Cirrus CS8420 Digital audio sample rate converter Datasheet

CS8420
Digital Audio Sample Rate Converter
Features
General Description
 Complete IEC60958, AES3, S/PDIF, EIAJ
The CS8420 is a stereo digital audio sample rate converter (SRC) with AES3-type and serial digital audio
inputs, AES3-type and serial digital audio outputs, and
includes comprehensive control ability via a 4-wire microcontroller port. Channel status and user data can be
assembled
in
block-sized
buffers,
making
read/modify/write cycles easy.
CP1201-compatible Transceiver with
Asynchronous Sample Rate Converter
 Flexible 3-wire Serial Digital I/O Ports
 8-kHz to 108-kHz Sample Rate Range
 1:3 and 3:1 Maximum Input to Output Sample
Rate Ratio
 128 dB Dynamic Range
 -117 dB THD+N at 1 kHz
 Excellent Performance at Almost a 1:1 Ratio
 Excellent Clock Jitter Rejection
 Pin and Microcontroller Read/Write Access to
Channel Status and User Data
 Microcontroller and Stand-Alone Modes
VA+ AGND FILT
Target applications include CD-R, DAT, MD, DVD and
VTR equipment, mixing consoles, digital audio transmission equipment, high-quality D/A and A/D
converters, effects processors, and computer audio
systems.
VD+ DGND
RERR RMCK
Serial
Audio
Input
Sample
Rate
Converter
RXP
Receiver
RXN
Misc.
Control
H/S
The CS8420 is available in a 28-pin SOIC package in
both Commercial (-10º to +70º C) and Automotive
grades (-40º to +85º C). The CDB8420 Customer Demonstration board is also available for device evaluation
and implementation suggestions.
Please refer to “Ordering Information” on page 93 for ordering information.
 24-bit I/O Words
ILRCK
ISCLK
SDIN
Digital audio inputs and outputs may be 24, 20, or 16
bits. The input data can be completely asynchronous to
the output data, with the output data being synchronous
to an external system clock.
RST
http://www.cirrus.com
Clock &
Data
Recovery
AES3
S/PDIF
Decoder
C & U bit
Data
Buffer
Control
Port &
Registers
EMPH U TCBL SDA/
SCL/ AD1/ AD0/ INT
CDOUT CCLK CDIN CS
Copyright © Cirrus Logic, Inc. 2007
(All Rights Reserved)
Serial
Audio
Output
AES3
S/PDIF
Encoder
OLRCK
OSCLK
SDOUT
TXP
Driver
TXN
Output
Clock
Generator
OMCK
APRIL '07
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CS8420
TABLE OF CONTENTS
1. CHARACTERISTICS AND SPECIFICATIONS ...................................................................................... 6
SPECIFIED OPERATING CONDITIONS .............................................................................................. 6
ABSOLUTE MAXIMUM RATINGS ........................................................................................................ 6
PERFORMANCE SPECIFICATIONS .................................................................................................... 7
DIGITAL FILTER CHARACTERISTICS ................................................................................................. 7
DC ELECTRICAL SPECIFICATIONS .................................................................................................... 7
DIGITAL INPUT CHARACTERISTICS .................................................................................................. 8
DIGITAL INTERFACE SPECIFICATIONS ............................................................................................. 8
TRANSMITTER CHARACTERISTICS .................................................................................................. 8
SWITCHING CHARACTERISTICS ....................................................................................................... 8
SWITCHING CHARACTERISTICS - SERIAL AUDIO PORTS .............................................................. 9
SWITCHING CHARACTERISTICS - CONTROL PORT - SPI™ MODE ............................................. 10
SWITCHING CHARACTERISTICS - CONTROL PORT - I²C® MODE ............................................... 11
2. TYPICAL CONNECTION DIAGRAM ................................................................................................... 12
3. GENERAL DESCRIPTION ................................................................................................................... 13
4. DATA I/O FLOW AND CLOCKING OPTIONS ..................................................................................... 14
5. SAMPLE RATE CONVERTER (SRC) .................................................................................................. 18
5.1 Dither ............................................................................................................................................. 18
5.2 SRC Locking, Varispeed and the Sample Rate Ratio Register ..................................................... 18
6. THREE-WIRE SERIAL AUDIO PORTS ............................................................................................... 19
7. AES3 TRANSMITTER AND RECEIVER .............................................................................................. 22
7.1 AES3 Receiver ............................................................................................................................... 22
7.1.1 PLL, Jitter Attenuation, and Varispeed .................................................................................. 22
7.1.2 OMCK Out On RMCK ........................................................................................................... 22
7.1.3 Error Reporting and Hold Function ........................................................................................ 22
7.1.4 Channel Status Data Handling .............................................................................................. 23
7.1.5 User Data Handling ............................................................................................................... 23
7.1.6 Non-Audio Auto Detection ..................................................................................................... 24
7.2 AES3 Transmitter ........................................................................................................................... 24
7.2.1 Transmitted Frame and Channel Status Boundary Timing ................................................... 24
7.2.2 TXN and TXP Drivers ............................................................................................................ 25
7.3 Mono Mode Operation ................................................................................................................... 25
8. AES3 TRANSMITTER AND RECEIVER .............................................................................................. 28
8.1 Sample Rate Converter ................................................................................................................. 28
8.2 Non-SRC Delay ............................................................................................................................. 29
9. CONTROL PORT DESCRIPTION AND TIMING ................................................................................. 30
9.1 SPI Mode ....................................................................................................................................... 30
9.2 I²C Mode ........................................................................................................................................ 31
9.3 Interrupts ........................................................................................................................................ 31
10. CONTROL PORT REGISTER BIT DEFINITIONS ............................................................................. 32
10.1 Memory Address Pointer (MAP) .................................................................................................. 32
10.2 Miscellaneous Control 1 (01h) ..................................................................................................... 34
10.3 Miscellaneous Control 2 (02h) ..................................................................................................... 35
10.4 Data Flow Control (03h) ............................................................................................................... 36
10.5 Clock Source Control (04h) .......................................................................................................... 37
10.6 Serial Audio Input Port Data Format (05h) ................................................................................... 38
10.7 Serial Audio Output Port Data Format (06h) ................................................................................ 39
10.8 Interrupt 1 Register Status (07h) (Read Only) ............................................................................. 40
10.9 Interrupt Register 2 Status (08h) (Read Only) ............................................................................. 41
10.10 Interrupt 1 Register Mask (09h) ................................................................................................. 41
10.11 Interrupt Register 1 Mode Registers MSB & LSB (0Ah,0Bh) ..................................................... 41
10.12 Interrupt 2 Register Mask (0Ch) ................................................................................................. 42
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CS8420
10.13 Interrupt Register 2 Mode Registers MSB & LSB (0Dh,0Eh) ..................................................... 42
10.14 Receiver Channel Status (0Fh) (Read Only) ............................................................................. 43
10.15 Receiver Error (10h) (Read Only) .............................................................................................. 44
10.16 Receiver Error Mask (11h) ......................................................................................................... 45
10.17 Channel Status Data Buffer Control (12h) ................................................................................. 45
10.18 User Data Buffer Control (13h) .................................................................................................. 46
10.19 Sample Rate Ratio (1Eh) (Read Only) ....................................................................................... 47
10.20 C-Bit or U-Bit Data Buffer (20h - 37h) ........................................................................................ 47
10.21 CS8420 I.D. and Version Register (7Fh) (Read Only) ............................................................... 47
11. SYSTEM AND APPLICATIONS ISSUES ........................................................................................... 48
11.1 Reset, Power Down and Start-up Options ................................................................................... 48
11.2 Transmitter Startup ...................................................................................................................... 48
11.3 SRC Invalid State ......................................................................................................................... 49
11.4 C/U Buffer Data Corruption .......................................................................................................... 49
11.5 Block-Mode U-Data D-to-E Buffer Transfers ............................................................................... 50
11.6 ID Code and Revision Code ........................................................................................................ 50
11.7 Power Supply, Grounding, and PCB layout ................................................................................. 50
11.8 Synchronization of Multiple CS8420s .......................................................................................... 50
11.9 Extended Range Sample Rate Conversion ................................................................................. 50
12. SOFTWARE MODE - PIN DESCRIPTION ......................................................................................... 51
13. HARDWARE MODES ......................................................................................................................... 55
13.1 Overall Description ....................................................................................................................... 55
13.1.1 Hardware Mode Definitions ................................................................................................. 55
13.1.2 Serial Audio Port Formats ................................................................................................... 55
13.2 Hardware Mode 1 Description (DEFAULT Data Flow, AES3 Input) ............................................ 56
13.2.1 Pin Description - Hardware Mode 1 .................................................................................... 57
13.3 Hardware Mode 2 Description ..................................................................................................... 59
13.3.1 Pin Description - Hardware Mode 2 .................................................................................... 61
13.4 Hardware Mode 3 Description ..................................................................................................... 63
13.4.1 Pin Description - Hardware Mode 3 .................................................................................... 65
13.5 Hardware Mode 4 Description ..................................................................................................... 67
13.5.1 Pin Description - Hardware Mode 4 .................................................................................... 69
13.6 Hardware Mode 5 Description ..................................................................................................... 71
13.6.1 Pin Description - Hardware Mode 5 .................................................................................... 72
13.7 Hardware Mode 6 Description ..................................................................................................... 74
13.7.1 Pin Description - Hardware Mode 6 .................................................................................... 76
14. EXTERNAL AES3/SPDIF/IEC60958 TRANSMITTER AND RECEIVER COMPONENTS ................ 78
14.1 AES3 Transmitter External Components ..................................................................................... 78
14.2 AES3 Receiver External Components ......................................................................................... 79
14.3 Isolating Transformer Requirements ............................................................................................ 80
15. CHANNEL STATUS AND USER DATA BUFFER MANAGEMENT .................................................. 81
15.1 AES3 Channel Status(C) Bit Management .................................................................................. 81
15.1.1 Manually Accessing the E Buffer ......................................................................................... 82
15.1.2 Reserving the First 5 Bytes in the E Buffer ......................................................................... 83
15.1.3 Serial Copy Management System (SCMS) ......................................................................... 83
15.1.4 Channel Status Data E Buffer Access ................................................................................. 83
15.1.5 One-Byte Mode ................................................................................................................... 84
15.1.6 Two-Byte Mode ................................................................................................................... 84
15.2 AES3 User (U) Bit Management .................................................................................................. 84
15.2.1 Mode 1: Transmit All Zeros ................................................................................................. 84
15.2.2 Mode 2: Block Mode ............................................................................................................ 84
15.2.3 IEC60958 Recommended U Data Format for Consumer Applications ............................... 85
15.2.4 Mode (3): Reserved ............................................................................................................. 85
15.2.5 Mode (4): IEC Consumer B ................................................................................................. 85
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CS8420
16. PLL FILTER ........................................................................................................................................ 87
16.1 General ........................................................................................................................................ 87
16.2 External Filter Components ......................................................................................................... 87
16.2.1 General ................................................................................................................................ 87
16.2.2 Capacitor Selection ............................................................................................................. 88
16.2.3 Circuit Board Layout ............................................................................................................ 88
16.3 Component Value Selection ........................................................................................................ 88
16.3.1 Identifying the Part Revision ................................................................................................ 88
16.3.2 Locking to the RXP/RXN Receiver Inputs ........................................................................... 89
16.3.3 Locking to the ILRCK Input ................................................................................................. 89
16.3.4 Jitter Tolerance .................................................................................................................... 90
16.3.5 Jitter Attenuation ................................................................................................................. 90
17. PARAMETER DEFINITIONS .............................................................................................................. 91
18. PACKAGE DIMENSIONS .................................................................................................................. 92
THERMAL CHARACTERISTICS AND SPECIFICATIONS ................................................................. 92
19. ORDERING INFORMATION .............................................................................................................. 93
20. REVISION HISTORY .......................................................................................................................... 93
LIST OF FIGURES
Figure 1.Audio Port Master Mode Timing ................................................................................................... 9
Figure 2.Audio Port Slave Mode and Data Input Timing ............................................................................. 9
Figure 3.SPI Mode Timing ........................................................................................................................ 10
Figure 4.I²C Mode Timing ......................................................................................................................... 11
Figure 5.Recommended Connection Diagram for Software Mode ........................................................... 12
Figure 6.Software Mode Audio Data Flow Switching Options ................................................................... 14
Figure 7.CS8420 Clock Routing ................................................................................................................ 14
Figure 8.Serial Audio Input, using PLL, SRC Enabled .............................................................................. 16
Figure 9.Serial Audio Input, No PLL, SRC Enabled .................................................................................. 16
Figure 10.AES3 Input, SRC Enabled ........................................................................................................ 16
Figure 11.Serial Audio Input, AES3 Input Clock Source, SRC Enabled ................................................... 16
Figure 12.Serial Audio Input, SRC Output Clocked by AES3 Recovered Clock ....................................... 16
Figure 13.AES3 Input, SRC to Serial Audio Output, Serial Audio Input to AES3 Out ............................... 16
Figure 14.AES3 Input to Serial Audio Output, Serial Audio Input to AES3 Out, No SRC ......................... 17
Figure 15.AES3 Input to Serial Audio Output Only ................................................................................... 17
Figure 16.Input Serial Port to AES3 Transmitter ....................................................................................... 17
Figure 17.Serial Audio Input Example Formats ........................................................................................ 20
Figure 18.Serial Audio Output Example Formats ...................................................................................... 21
Figure 19.AES3 Receiver Timing for C & U Pin Output Data ................................................................... 23
Figure 20.AES3 Transmitter Timing for C, U and V Pin Input Data .......................................................... 26
Figure 21.Mono Mode Operation Compared to Normal Stereo Operation ............................................... 27
Figure 22.Control Port Timing in SPI Mode .............................................................................................. 30
Figure 23.Control Port Timing in I²C Mode ............................................................................................... 31
Figure 24.Hardware Mode 1 - Default Data Flow, AES3 Input ................................................................. 56
Figure 25.Hardware Mode 2 - Default Data Flow, Serial Audio Input ....................................................... 59
Figure 26.Hardware Mode 3 - Transceive Data Flow, with SRC .............................................................. 63
Figure 27.Hardware Mode 4 - Transceive Data Flow, Without SRC ......................................................... 67
Figure 28.Hardware Mode 5 - AES3 Receiver Only ................................................................................. 71
Figure 29.Hardware Mode 6 - AES3 Transmitter Only ............................................................................. 74
Figure 30.Professional Output Circuit ....................................................................................................... 78
Figure 31.Consumer Output Circuit .......................................................................................................... 78
Figure 32.TTL/CMOS Output Circuit ......................................................................................................... 79
Figure 33.Professional Input Circuit .......................................................................................................... 79
Figure 34.Transformerless Professional Input Circuit ............................................................................... 79
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CS8420
Figure 35.Consumer Input Circuit ............................................................................................................. 80
Figure 36.TTL/CMOS Input Circuit ............................................................................................................ 80
Figure 37.Channel Status Data Buffer Structure ....................................................................................... 81
Figure 38.Channel Status Block Handling When Fso is Not Equal to Fsi ................................................. 82
Figure 39.Flowchart for Reading the E Buffer ........................................................................................... 82
Figure 40.Flowchart for Writing the E Buffer ............................................................................................. 83
Figure 41.PLL Block Diagram ................................................................................................................... 87
Figure 42.Recommended Layout Example ............................................................................................... 88
Figure 43.Jitter Tolerance Template ......................................................................................................... 90
Figure 44.Revision D Jitter Attenuation ..................................................................................................... 90
Figure 45.Revision D1 Jitter Attenuation ................................................................................................... 90
LIST OF TABLES
Table 1. Minimizing Group Delay Through Multiple CS8420s When Locking to RXP/RXN ...................... 28
Table 2. Minimizing Group Delay Through Multiple CS8420s When Locking to ILRCK ........................... 28
Table 3. Non-SRC Delay ........................................................................................................................... 29
Table 4. Summary of all Bits in the Control Register Map ........................................................................ 33
Table 5. Hardware Mode Definitions ......................................................................................................... 55
Table 6. Serial Audio Output Formats Available in Hardware Mode ......................................................... 55
Table 7. Serial Audio Input Formats Available in Hardware Mode ............................................................ 55
Table 8. Hardware Mode 1 Start-Up Options ............................................................................................ 56
Table 9. HW Mode 2A COPY/C and ORIG/U Pin Function ...................................................................... 60
Table 10. HW Mode 2 Serial Audio Port Format Selection ....................................................................... 60
Table 11. Hardware Mode 2 Start-Up Options .......................................................................................... 60
Table 12. Hardware Mode 3 Start-Up Options .......................................................................................... 64
Table 13. Hardware Mode 4 Start-Up Options .......................................................................................... 68
Table 14. Hardware Mode 5 Start-Up Options .......................................................................................... 71
Table 15. HW 6 COPY/C and ORIG Pin Function .................................................................................... 75
Table 16. HW 6 Serial Port Format Selection ........................................................................................... 75
Table 17. Second Line Part Marking ......................................................................................................... 88
Table 18. Locking to RXP/RXN - Fs = 8 to 96 kHz ................................................................................... 89
Table 19. Locking to RXP/RXN - Fs = 32 to 96 kHz* ................................................................................ 89
Table 20. Locking to the ILRCK Input ....................................................................................................... 89
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CS8420
1.
CHARACTERISTICS AND SPECIFICATIONS
All Min/Max characteristics and specifications are guaranteed over the Specified Operating Conditions. Typical
performance characteristics and specifications are derived from measurements taken at nominal supply voltages
and TA = 25°C.
SPECIFIED OPERATING CONDITIONS
AGND, DGND = 0 V, all voltages with respect to 0 V.
Parameter
Power Supply Voltage
Ambient Operating Temperature:
Commercial Grade
Automotive Grade
Symbol
Min
Typ
Max
Units
VD+, VA+
4.75
5.0
5.25
V
TA
-10
-40
-
+70
+85
°C
°C
ABSOLUTE MAXIMUM RATINGS
AGND, DGND = 0 V; all voltages with respect to 0 V. Operation beyond these limits may result in permanent damage to the device. Normal operation is not guaranteed at these extremes.
Parameter
Symbol
Min
Max
Units
VD+, VA+
-
6.0
V
Input Current, Any Pin Except Supplies, RXP/RXN (Note 1)
Iin
-
±10
mA
Input Voltage
Vin
-0.3
(VD+) + 0.3
V
Ambient Operating Temperature (power applied)
TA
-55
125
°C
Storage Temperature
Tstg
-65
150
°C
Power Supply Voltage
Notes:
1. Transient currents of up to 100 mA will not cause SCR latch-up.
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CS8420
PERFORMANCE SPECIFICATIONS
Parameter*
Symbol
Dynamic Range
Min
Typ
Max
Units
120
128
-
dB
Fsi
8
-
108
kHz
Fso
8
-
108
kHz
0.33
-
3
-
-
-117
-112
-110
-107
dB
dB
dB
dB
-
-
-140
dBFS
Resolution
16
-
24
bits
Gain Error
-0.12
-
0
dB
Input Sample Rate
(serial input port)
Output Sample Rate
Output to Input Sample Rate Ratio
THD+N
Total Harmonic Distortion + Noise
1 kHz, -1 dBFS, 0.33 < Fso/Fsi < 1.7
1 kHz, -1 dBFS, 0.33 < Fso/Fsi < 3
10 kHz, -1 dBFS, 0.33 < Fso/Fsi < 1.7
10 kHz, -1 dBFS, 0.33 < Fso/Fsi < 3
Peak idle channel noise component
DIGITAL FILTER CHARACTERISTICS
Parameter*
Passband
Symbol
Min
Typ
Max
Units
0
0
-
0.4535*Fsi
0.4535*Fso
Hz
Hz
-
-
±0.007
dB
0.5465*Fso
-
Fsi/2
Hz
110
-
-
dB
tgd
-
-
1.75
ms
Δtgd
-
-
0.0
μs
-
-
0.0
°
Upsampling
Downsampling
Passband Ripple
Stopband (Downsampling)
Stopband Attenuation
Group Delay
(Note 2)
Group Delay Variation vs. Frequency
Interchannel Phase Deviation
2. See “AES3 Transmitter and Receiver” on page 28.
DC ELECTRICAL SPECIFICATIONS
AGND = DGND = 0 V; all voltages with respect to 0 V.
Parameters
Symbol
Min
Typ
Max
Units
VA+
VD+
-
20
20
-
μA
μA
Supply Current at 48 kHz Fso and Fsi
VA+
VD+
-
3.7
66
-
mA
mA
Supply Current at 96 kHz Fso and Fsi
VA+
VD+
-
7.0
125
-
mA
mA
Power Down Mode (Note 3)
Supply Current in power down
Normal Operation (Note 4)
3. Power Down Mode is defined as RST = LO with all clocks and data lines held static.
4. Normal operation is defined as RST = HI.
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CS8420
DIGITAL INPUT CHARACTERISTICS
Parameters
Input Leakage Current
Differential Input Voltage, RXP to RXN
Symbol
Min
Typ
Max
Units
Iin
-
±10
±15
μA
VTH
200
-
-
mVpp
DIGITAL INTERFACE SPECIFICATIONS
AGND = DGND = 0 V; all voltages with respect to 0 V.
Parameters
Symbol
Min
Max
Units
High-Level Output Voltage (IOH = -3.2 mA), except TXP/TXN
VOH
(VD+) - 1.0
-
V
Low-Level Output Voltage (IOH = 3.2 mA), except TXP/TXN
VOL
-
0.4
V
High-Level Output Voltage (IOH = -21 mA), TXP, TXN
(VD+) - 0.7
-
V
Low-Level Output Voltage (IOH = 21 mA), TXP, TXN
-
0.7
V
High-Level Input Voltage, except RXP, RXN
VIH
2.0
(VD+) + 0.3
V
Low-Level Input Voltage, except RXP, RXN
VIL
-0.3
0.8
V
TRANSMITTER CHARACTERISTICS
Parameters
Symbol
Typ
Units
TXP Output Resistance
RTXP
25
Ω
TXN Output Resistance
RTXN
25
Ω
SWITCHING CHARACTERISTICS
Inputs: Logic 0 = 0 V, Logic 1 = VD+; CL = 20 pF.
Parameter
Symbol
RST pin Low Pulse Width
OMCK Frequency for OMCK = 512 * Fso
OMCK Low and High Width for OMCK = 512 * Fso
Min
Typ
Max
Units
200
-
-
μs
4.096
-
55.3
MHz
8.2
-
-
ns
OMCK Frequency for OMCK = 384 * Fso
3.072
-
41.5
MHz
OMCK Low and High Width for OMCK = 384 * Fso
12.3
-
-
ns
OMCK Frequency for OMCK = 256 * Fso
2.048
-
27.7
MHz
OMCK Low and High Width for OMCK = 256 * Fso
16.4
-
-
ns
8.0
-
108.0
kHz
-
200
-
ps RMS
40
50
60
%
27.7
MHz
PLL Clock Recovery Sample Rate Range
RMCK output jitter
(Note 5)
RMCK output duty cycle
RMCK Input Frequency
(Note 6)
2.048
-
RMCK Input Low and High Width
(Note 6)
16.4
-
-
ns
-
-
1
ns
AES3 Transmitter Output Jitter
5. Cycle-to-cycle jitter using 32-96 kHz external PLL components.
6. PLL is bypassed (RXD1:0 bits in the Clock Source Control register set to 10b), clock is input to the RMCK
pin.
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CS8420
SWITCHING CHARACTERISTICS - SERIAL AUDIO PORTS
Inputs: Logic 0 = 0 V, Logic 1 = VD+; CL = 20 pF.
Parameter
Symbol
Min
Typ
Max
Units
OSCLK Active Edge to SDOUT Output Valid
(Note 7)
tdpd
-
-
25
ns
SDIN Setup Time Before ISCLK Active Edge
(Note 7)
tds
20
-
-
ns
SDIN Hold Time After ISCLK Active Edge
(Note 7)
tdh
20
-
-
ns
(Note 7, 8)
tsmd
0
-
16
ns
(Note 9)
tlmd
0
-
17
ns
-
50
-
%
tsckw
36
-
-
ns
tsckl
14
-
-
ns
I/OSCLK Input High Width
tsckh
14
-
-
ns
I/OSCLK Active Edge to I/OLRCK Edge
tlrckd
20
-
-
ns
tlrcks
20
-
-
ns
Master Mode
O/RMCK to I/OSCLK active edge delay
O/RMCK to I/OLRCK delay
I/OSCLK and I/OLRCK Duty Cycle
Slave Mode
I/OSCLK Period
(Note 10)
I/OSCLK Input Low Width
(Note 7, 9, 11)
I/OLRCK Edge Setup Before I/OSCLK Active Edge
(Note 7, 9, 12)
7. The active edges of ISCLK and OSCLK are programmable.
8. When OSCLK, OLRCK, ISCLK, and ILRCK are derived from OMCK they are clocked from its rising edge.
When these signals are derived from RMCK, they are clocked from its falling edge.
9. The polarity of ILRCK and OLRCK is programmable.
10. No more than 128 SCLK per frame.
11. This delay is to prevent the previous I/OSCLK edge from being interpreted as the first one after I/OLRCK
has changed.
12. This setup time ensures that this I/OSCLK edge is interpreted as the first one after I/OLRCK has changed.
ISCLK
OSCLK
(output)
ILRCK
OLRCK
(input)
ILRCK
O LRCK
(output)
t lrcks
t sckh
t sckl
ISCLK
OSCLK
(input)
t sm d
t
t lrckd
lm d
t sckw
RM CK
(output)
Hardware M ode
SDIN
RM CK
(output)
t ds
t dh
t dpd
Software M ode
O M CK
(input)
Figure 1. Audio Port Master Mode Timing
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SDOUT
Figure 2. Audio Port Slave Mode and Data Input Timing
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CS8420
SWITCHING CHARACTERISTICS - CONTROL PORT - SPI™ MODE
Inputs: Logic 0 = 0 V, Logic 1 = VD+; CL = 20 pF.
Parameter
Symbol
Min
Typ
Max
Units
fsck
0
-
6.0
MHz
CS High Time Between Transmissions
tcsh
1.0
-
-
μs
CCLK Clock Frequency
(Note 13)
CS Falling to CCLK Edge
tcss
20
-
-
ns
CCLK Low Time
tscl
66
-
-
ns
CCLK High Time
tsch
66
-
-
ns
CDIN to CCLK Rising Setup Time
tdsu
40
-
-
ns
CCLK Rising to DATA Hold Time
tdh
18
-
-
ns
CCLK Falling to CDOUT Stable
(Note 14)
tpd
-
-
45
ns
Rise Time of CDOUT
tr1
-
-
25
ns
Fall Time of CDOUT
tf1
-
-
25
ns
Rise Time of CCLK and CDIN
(Note 15)
tr2
-
-
100
ns
Fall Time of CCLK and CDIN
(Note 15)
tf2
-
-
100
ns
13. If Fso or Fsi is lower than 46.875 kHz, the maximum CCLK frequency should be less than 128 Fso and
less than 128 Fsi. This is dictated by the timing requirements necessary to access the Channel Status and
User Bit buffer memory. Access to the control register file can be carried out at the full 6 MHz rate. The
minimum allowable input sample rate is 8 kHz, so choosing CCLK to be less than or equal to 1.024 MHz
should be safe for all possible conditions.
14. Data must be held for sufficient time to bridge the transition time of CCLK.
15. For fsck < 1 MHz.
CS
t scl
t css
t sch
t csh
CCLK
t r2
t f2
CDIN
t dsu
t dh
t pd
CDOUT
Figure 3. SPI Mode Timing
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SWITCHING CHARACTERISTICS - CONTROL PORT - I²C® MODE
Inputs: Logic 0 = 0 V, Logic 1 = VD+; CL = 20 pF.
Parameter
Symbol
Min
Typ
Max
Units
SCL Clock Frequency
fscl
-
-
100
kHz
Bus Free Time Between Transmissions
tbuf
4.7
-
-
μs
Start Condition Hold Time (prior to first clock pulse)
thdst
4.0
-
-
μs
Clock Low Time
tlow
4.7
-
-
μs
Clock High Time
thigh
4.0
-
-
μs
Setup Time for Repeated Start Condition
tsust
4.7
-
-
μs
thdd
0
-
-
μs
tsud
250
-
-
ns
Rise Time of Both SDA and SCL Lines
tr
-
-
25
ns
Fall Time of Both SDA and SCL Lines
tf
-
-
25
ns
tsusp
4.7
-
-
μs
SDA Hold Time from SCL Falling
(Note 16)
SDA Setup Time to SCL Rising
Setup Time for Stop Condition
16. Data must be held for sufficient time to bridge the 25 ns transition time of SCL.
Stop
Repeated
Start
Start
Stop
SDA
t buf
t
t high
t hdst
tf
hdst
t susp
SCL
t
low
t
hdd
t sud
t sust
tr
Figure 4. I²C Mode Timing
DS245F4
11
CS8420
2.
TYPICAL CONNECTION DIAGRAM
+5V
Analog
Supply *
Ferrite *
Bead
VA+
AES3/
SPDIF
Source
Cable
Termination
+5V
Digital
Supply
0.1μF
0.1μF
VD+
TXP
TXN
RXP
RXN
Cable
Interface
CS8420
OLRCK
OSCLK
SDOUT
3-wire Serial
Audio Source
ILRCK
ISCLK
SDIN
Clock Source
and Control
SDA/CDOUT
AD0 / CS
SCL/CCLK
AD1/CDIN
INT
EMPH / AD2
U
RERR
RST
TCBL
H/S
AGND FILT
DGND
47kΩ
Hardware
Control
To other
CS8420's
AES3/
SPDIF
Equipment
3-wire Serial
Audio Input
Device
RMCK
OMCK
Microcontroller
RFILT
CFILT
CRIP
* A separate analog supply is only necessary in applications where
RMCK is used for a jitter sensitive task. For applications where
RMCK is not used for a jitter sensitive task, connect VA+ to VD+
via a ferrite bead. Keep the decoupling capacitor between VA+
and AGND.
Figure 5. Recommended Connection Diagram for Software Mode
12
DS245F4
CS8420
3.
GENERAL DESCRIPTION
The CS8420 is a fully asynchronous sample rate converter plus AES3 transceiver intended to be used in digital audio systems. Such systems include digital mixing consoles, effects processors, tape recorders, and computer multimedia systems. The CS8420 is intended for 16-, 20-, and 24-bit applications where the input sample rate is
unknown, or is known to be asynchronous to the system sample rate.
On the input side of the CS8420, AES3 or 3-wire serial format can be chosen. The output side produces both AES3
and 3-wire serial format. An I²C/SPI-compatible microcontroller interface allows full block processing of channel status and user data via block reads from the incoming AES3 data stream and block writes to the outgoing AES3 data
stream. The user can also access information decoded from the input AES3 data stream, such as the presence of
non-audio data and pre-emphasis, as well as control the various modes of the device. For users who prefer not to
use a micro-controller, six hardware modes have been provided and documented towards the end of this data sheet.
In these modes, flexibility is limited, with pins providing some programmability.
When used for AES3-input/AES3-output applications, the CS8420 can automatically transceive user data that conforms to the IEC60958-recommended format. The CS8420 also allows access to the relevant bits in the AES3 data
stream to comply with the serial copy management system (SCMS).
The diagram on the cover of this data sheet shows the main functional blocks of the CS8420. Figure 5 shows the
supply and external connections to the device.
Familiarity with the AES3 and IEC60958 specifications are assumed throughout this document. Application Note 22:
Overview of Digital Audio Interface Data Structures, contains a tutorial on digital audio specifications. The paper An
Understanding and Implementation of the SCMS Serial Copy Management System for Digital Audio Transmission,
by Clif Sanchez, is an excellent tutorial on SCMS. It may be obtained from Cirrus Logic, Inc., or from the AES.
To guarantee system compliance, the proper standards documents should be obtained. The latest AES3 standard
should be obtained from the Audio Engineering Society (ANSI), the latest IEC60958 standard from the International
Electrotechnical Commission and the latest EIAJ CP-1201 standard from the Japanese Electronics Bureau.
DS245F4
13
CS8420
4.
DATA I/O FLOW AND CLOCKING OPTIONS
The CS8420 can be configured for nine connectivity alternatives, referred to as data flows. Each data flow has an
associated clocking set-up. Figure 6 shows the data flow switching, along with the control register bits which control
the switches. This drawing only shows the audio data paths for simplicity. Figure 7 shows the internal clock routing
and the associated control register bits. The clock routing constraints determine which data routing options are actually usable.
SPD1-0
ILRCK
ISCLK
SDIN
Serial
Audio
Input
Serial
Audio
Output
SRCD
Sample
Rate
Converter
RXN
AESBP TXOFF
AES3
Receiver
RXP
OLRCK
OSCLK
SDOUT
TXP
AES3
Encoder
TXN
TXD1-0
Figure 6. Software Mode Audio Data Flow Switching Options
SDIN
ISCLK
ILRCK
SIMS
SERIAL
SAMPLE
RATE
CONVERTER
AUDIO
INPUT
RXD0
1
0
÷
PLL
MUX
RXP
1
1
OSCLK
OLRCK
0
TXN
CHANNEL
STATUS
MEMORY
AES3
TRANSMIT
TXP
USER
BIT
0
MUX
SDOUT
INC
MUX
RMCKF
SERIAL
AUDIO
OUTPUT
SWCLK
UNLOCK
MEMORY
OUTC
MUX
1
0
0
MUX
RMCK
÷
1
RXD1
OMCK
CLK[1:0]
*Note: When SWCLK mode is enabled, signal input on OMCK is only output through RMCK and not
routed back through the RXD1 multiplexer; RMCK is not bi-directional in this mode.
Figure 7. CS8420 Clock Routing
14
DS245F4
CS8420
The AESBP switch allows a TTL level, bi-phase mark-encoded data stream connected to RXP to be routed to the
TXP and TXN pin drivers. The TXOFF switch causes the TXP and TXN outputs to be driven to ground
In modes including the SRC function, there are two audio-data-related clock domains. One domain includes the input side of SRC, plus the attached data source. The second domain includes the output side of the SRC, plus any
attached output ports.
There are two possible clock sources. The first known as the recovered clock, is the output of a PLL, and is connected to the RCMK pin. The input to the PLL can be either the incoming AES3 data stream or the ILRCK word rate
clock from the serial audio input port. The second clock is input via the OMCK pin, and would normally be a crystalderived stable clock. The Clock Source Control Register bits determine which clock is connected to which domain.
By studying the following drawings, and appropriately setting the Data Flow Control and Clock Source Control register bits, the CS8420 can be configured to fit a variety of application requirements.
The following drawings illustrate the possible valid data flows. The audio data flow is indicated by the thin lines; the
clock routing is indicated by the bold lines. The register settings for the Data Flow Control register and the Clock
Source Register are also shown for each data flow. Some of the register settings may appear to be not relevant to
the particular data flow in question, but have been assigned a particular state. This is done to minimize power consumption. The AESBP data path from the RXP pin to the AES3 output drivers, and the TXOFF control, have been
omitted for clarity, but are present and functional in all modes where the AES3 transmitter is in use.
Figures 8 and 9 show audio data entering via the serial audio input port, then passing through the sample rate converter, and then output both to the serial audio output port and to the AES3 transmitter. Figure 8 shows the PLL
recovering the input clock from ILRCK word clock. Figure 9 shows using a direct 256*Fsi clock input via the RMCK
pin, instead of the PLL.
Figure 10 shows audio data entering via the AES3 Receiver. The PLL locks onto the pre-ambles in the incoming
audio stream, and generates a 256*Fsi clock. The rate-converted data is then output via the serial audio output port
and via the AES3 transmitter.
Figure 11 shows the same data flow as Figure 8. The input clock is derived from an incoming AES3 data stream.
The incoming data must be synchronous to the AES3 data stream.
Figure 12 shows the same data flow as Figure 8. The input data must be synchronous to OMCK. The output data
is clocked by the recovered PLL clock from an AES3 input stream. This may be used to implement a “house sync”
architecture.
Figure 8 shows audio data entering via the AES3 receiver, passing through the sample rate converter, and then exiting via the serial audio output port. Synchronous audio data may then be input via the serial audio input port and
output via the AES3 transmitter.
Figure 14 is the same as Figure 13, but without the sample rate converter. The whole data path is clocked via the
PLL generated recovered clock.
Figure 15 illustrates a standard AES3 receiver function, with no rate conversion.
Figure 16 shows a standard AES3 transmitter function, with no rate conversion.
DS245F4
15
CS8420
Serial
Audio
Output
SDIN
ISCLK
ILRCK
Serial
Audio
Input
Sample
Rate
Converter
AES3
Encoder
& Driver
PLL
RMCK
OLRCK
OSCLK
SDOUT
TXP
RMCK
Clock Source Control Bits
OUTC: 0
INC:
0
RXD1-0: 00
Serial
Audio
Output
RXP
Sample
Rate
Converter
AES3
Encoder
& Driver
PLL
OLRCK
OSCLK
SDOUT
TXP
AES3
Encoder
& Driver
TXP
TXN
Clock Source Control Bits
OUTC: 0
INC:
0
RXD1-0: 10
Figure 9. Serial Audio Input, No PLL, SRC Enabled
SDIN
ISCLK
ILRCK
Serial
Audio
Input
RXN
AES3
Rx
TXN
OMCK
Data Flow Control Bits
TXD1-0: 00
SPD1-0: 00
SRCD: 1
OLRCK
OSCLK
SDOUT
OMCK
Data Flow Control Bits
TXD1-0: 00
SPD1-0: 00
SRCD: 0
RXP
RMCK
Sample
Rate
Converter
TXN
Figure 8. Serial Audio Input, using PLL, SRC Enabled
AES3
Rx &
Decode
Serial
Audio
Input
OMCK
Data Flow Control Bits
TXD1-0: 00
SPD1-0: 00
SRCD: 0
RXN
SDIN
ISCLK
ILRCK
Serial
Audio
Output
Sample
Rate
Converter
Serial
Audio
Output
OLRCK
OSCLK
SDOUT
AES3
Encoder
& Driver
TXP
TXN
PLL
RMCK OMCK
Clock Source Control Bits
OUTC: 0
0
INC:
RXD1-0: 01
Figure 10. AES3 Input, SRC Enabled
Data Flow Control Bits
TXD1-0: 00
SPD1-0: 00
SRCD: 0
Clock Source Control Bits
OUTC: 0
INC:
0
RXD1-0: 01
Figure 11. Serial Audio Input, AES3 Input Clock Source,
SDOUT OSCLK OLRCK SDIN ISCLK ILRCK
SDIN
ISCLK
ILRCK
Serial
Audio
Input
Sample
Rate
Converter
PLL
AES3
Rx
OMCK
RXP RXN
Data Flow Control Bits
TXD1-0: 00
SPD1-0: 00
SRCD: 0
Serial
Audio
Output
OLRCK
OSCLK
SDOUT
AES3
Encoder
& Driver
TXP
TXN
RXN
RXP
AES3
Sample
Rx &
Rate
Decode Converter
AES3
Encoder
& Driver
TXP
TXN
PLL
RMCK
Clock Source Control Bits
OUTC: 1
INC:
1
RXD1-0: 01
Figure 12. Serial Audio Input, SRC Output Clocked by
AES3 Recovered Clock
16
Serial Serial
Audio Audio
Output Input
RMCK
Data Flow Control Bits
TXD1-0: 01
SPD1-0: 00
SRCD: 1
OMCK
Clock Source Control Bits
OUTC: 0
INC:
0
RXD1-0: 01
Figure 13. AES3 Input, SRC to Serial Audio Output, Serial
Audio Input to AES3 Out
DS245F4
CS8420
SDOUT OSCLK OLRCK SDIN ISCLK ILRCK
Serial Serial
Audio Audio
Output Input
RXN
RXP
RXN
RXP
AES3
Rx &
Decode
AES3
Encoder
& Driver
AES3
Rx &
Decode
Serial
Audio
Output
OLRCK
OSCLK
SDOUT
TXP
PLL
TXN
PLL
RMCK
RMCK
Data Flow Control Bits
TXD1-0: 01
SPD1-0: 10
SRCD: 0
Data Flow Control Bits
TXD1-0: 10
SPD1-0: 10
SRCD: 0
TXOFF: 1
Clock Source Control Bits
OUTC: 1
INC:
0
RXD1-0: 01
Figure 14. AES3 Input to Serial Audio Output, Serial Audio Input to AES3 Out, No SRC
SDIN
ISCLK
ILRCK
Serial
Audio
Input
AES3
Encoder
& Driver
Clock Source Control Bits
OUTC: 1
INC:
0
RXD1-0: 01
Figure 15. AES3 Input to Serial Audio Output Only
TXP
TXN
OMCK
Data Flow Control Bits
TXD1-0: 01
SPD1-0: 01
SRCD: 0
Clock Source Control Bits
OUTC: 0
INC:
1
RXD1-0: 00
Figure 16. Input Serial Port to AES3 Transmitter
DS245F4
17
CS8420
5.
SAMPLE RATE CONVERTER (SRC)
Multirate digital signal processing techniques are used to conceptually upsample the incoming data to very high rate
and then downsample to the outgoing rate, resulting in a 24-bit output, regardless of the width of the input. The filtering is designed so that a full input audio bandwidth of 20 kHz is preserved if the input sample and output sample
rates are greater than 44.1 kHz. When the output sample rate becomes less than the input sample rate, the input is
automatically band limited to avoid aliasing products in the output. Careful design ensures minimum ripple and distortion products are added to the incoming signal. The SRC also determines the ratio between the incoming and
outgoing sample rates, and sets the filter corner frequencies appropriately. Any jitter in the incoming signal has little
impact on the dynamic performance of the rate converter and has no influence on the output clock.
5.1
Dither
When using the AES3 input, and when using the serial audio input port in Left-Justified and I²S modes, all
input data is treated as 24 bits wide. Any truncation that has been done prior to the CS8420 to less than 24
bits should have been done using an appropriate dither process. If the serial audio input port is used to feed
the SRC, and the port is in Right-Justified mode, then the input data will be truncated to the SIRES bit setting
value. If SIRES bits are set to 16 or 20 bits, and the input data is 24 bits wide, truncation distortion will occur.
Similarly, in any serial audio input port mode, if an inadequate number of bit clocks are entered (say 16 instead of 20), the input words will be truncated, causing truncation distortion at low levels. In summary, there
is no dithering mechanism on the input side of the CS8420, and care must be taken to ensure that no truncation occurs.
Dithering is used internally where appropriate inside the SRC block.
The output side of the SRC can be set to 16, 20, or 24 bits. Optional dithering can be applied, and is automatically scaled to the selected output word length. This dither is not correlated between left and right channels. It is recommended that the dither control bit be left in its default ON state.
5.2
SRC Locking, Varispeed and the Sample Rate Ratio Register
The SRC calculates the ratio between the input sample rate and the output sample rate and uses this information to set up various parameters inside the SRC block. The SRC takes some time to make this calculation. For a worst case 3:1 to 1:3 input sample rate transition, the SRC will take 9400/Fso to settle (195 ms
at Fso of 48 kHz). For a power-up situation, the SRC will start from 1:1; the worst case time becomes
8300/Fso (172 ms at Fso of 48 kHz).
If the PLL is in use (either AES3 or serial input port), the worst case locking time for the PLL and the SRC
is the sum of each locking time.
If Fsi is changing, for example in a varispeed application, the REUNLOCK interrupt will occur, and the SRC
will track the incoming sample rate. During this tracking mode, the SRC will still rate convert the audio data,
but at increased distortion levels. Once the incoming sample rate is stable, the REUNLOCK interrupt will
become false, and the SRC will return to normal levels of audio quality.
The VFIFO interrupt occurs if the data buffer in the SRC overflows, which can occur if the input sample rate
changes at >10%/second.
Varispeed at Fsi slew rates approaching 10%/sec is only supported when the input is via the serial audio
input port. When using the AES3 input, high frame rate slew rates will cause the PLL to lose lock.
The sample rate ratio is also made available as a register, accessible via the control port. The upper 2 bits
of this register form the integer part of the ratio, while the lower 6 bits form the fractional part. Since, in many
instances Fso is known, this allows the calculation of the incoming sample rate by the host microcontroller.
18
DS245F4
CS8420
6.
THREE-WIRE SERIAL AUDIO PORTS
A 3-wire serial audio input port and a 3-wire serial audio output port is provided. Each port can be adjusted to suit
the attached device via control registers. The following parameters are adjustable: master or slave, serial clock frequency, audio data resolution, left or right justification of the data relative to left/right clock, optional 1-bit cell delay
of the 1st data bit, the polarity of the bit clock and the polarity of the left/right clock. By setting the appropriate control
bits, many formats are possible.
Figure 17 shows a selection of common input formats, along with the control bit settings. The clocking of the input
section of the CS8420 may be derived from the incoming ILRCK word rate clock, using the on-chip PLL. The PLL
operation is described in the AES receiver description on page 22. In the case of use with the serial audio input port,
the PLL locks onto the leading edges of the ILRCK clock.
Figure 18 shows a selection of common output formats, along with the control bit settings. A special AES3 direct
output format is included, which allows serial output port access to the V, U, and C bits embedded in the serial audio
data stream. The P bit is replaced by a bit indicating the location of the start of a block. This format is only available
when the serial audio output port is being clocked by the AES3 receiver-recovered clock. Also, the received-channel
status block start signal is only available in Hardware mode 5, as the RCBL pin.
In Master mode, the left/right clock and the serial bit clock are outputs, derived from the appropriate clock domain
master clock.
In Slave mode, the left/right clock and the serial bit clock are inputs. The left/right clock must be synchronous to the
appropriate master clock, but the serial bit clock can be asynchronous and discontinuous if required. By appropriate
phasing of the left/right clock and control of the serial clocks, multiple CS8420’s can share one serial port. The
left/right clock should be continuous, but the duty cycle does not have to be 50%, provided that enough serial clocks
are present in each phase to clock all the data bits. When in Slave mode, the serial audio output port must be set to
left-justified or I²S data.
When using the serial audio output port in Slave mode with an OLRCK input which is asynchronous to the port’s
data source, then an interrupt bit is provided to indicate when repeated or dropped samples occur.
The CS8420 allows immediate mute of the serial audio output port audio data via a control register bit.
DS245F4
19
CS8420
ILRCK
Left
Justified
(In)
Channel A
ISCLK
SDIN
MSB
LSB
ILRCK
I²S
(In)
Channel B
MSB
LSB
Channel A
MSB
Channel B
ISCLK
SDIN
MSB
ILRCK
Right
Justified
(In)
MSB
LSB
MSB
LSB
Channel A
Channel B
ISCLK
SDIN
MSB
LSB
MSB
LSB
SIMS
SISF
SIRES1/0
SIJUST
SIDEL
SISPOL
SILRPOL
Left-Justified
X
X
00
0
0
0
0
I²S
X
X
00+
0
1
0
1
0
0
0
Right-Justified
X
X
XX*
1
X = don’t care to match format, but does need to be set to the desired setting
+ I²S can accept an arbitrary number of bits, determined by the number of ISCLK cycles
* not 11 - See Serial Input Port Data Format Register Bit Descriptions for an explanation of the meaning of each bit
Figure 17. Serial Audio Input Example Formats
20
DS245F4
CS8420
OLRCK
Left
Justified OSCLK
(Out)
SDOUT
Channel A
LSB
MSB
OLRCK
I²S
(Out)
MSB
LSB
Channel A
MSB
Channel B
OSCLK
SDOUT
LSB
MSB
OLRCK
Right
Justified OSCLK
(Out)
SDOUT
AES3
Direct
(Out)
Channel B
MSB
Channel A
MSB Extended
OLRCK
Channel B
MSB Extended
LSB
MSB
Channel B
Channel A
MSB
LSB
MSB
LSB
Channel A
Channel B
OSCLK
SDOUT
LSB
MSB V U C
LSB
MSB V U C
LSB
MSB V U C Z
LSB
MSB V U C Z
Frame 0
Frame 191
SOMS
SOSF
SORES1/0
SOJUST
SODEL
SOSPOL
SOLRPOL
Left-Justified
X
X
XX*
0
0
0
0
I²S
X
X
XX*
0
1
0
1
Right-Justified
1
X
XX*
1
0
0
0
AES3 Direct
X
X
11
0
0
0
0
X = don’t care to match format, but does need to be set to the desired setting
* not 11 - See Serial Output Data Format Register Bit Descriptions for an explanation of the meaning of each bit
Figure 18. Serial Audio Output Example Formats
DS245F4
21
CS8420
7.
AES3 TRANSMITTER AND RECEIVER
The CS8420 includes an AES3-type digital audio receiver and an AES3-type digital audio transmitter. A comprehensive buffering scheme provides read/write access to the channel status and user data. This buffering scheme is
described in “Channel Status and User Data Buffer Management” on page 81.
7.1
AES3 Receiver
The AES3 receiver accepts and decodes audio and digital data according to the AES3, IEC60958 (S/PDIF),
and EIAJ CP-1201 interface standards. The receiver consists of a differential input stage, accessed via pins
RXP and RXN, a PLL based clock recovery circuit, and a decoder which separates the audio data from the
channel status and user data.
External components are used to terminate and isolate the incoming data cables from the CS8420. These
components are detailed in “External AES3/SPDIF/IEC60958 Transmitter and Receiver Components” on
page 78.
7.1.1
PLL, Jitter Attenuation, and Varispeed
Please see “PLL Filter” on page 87 for general description of the PLL, selection of recommended PLL filter
components, and layout considerations. Figure 5 shows the recommended configuration of the two capacitors and one resistor that comprise the PLL filter.
7.1.2
OMCK Out On RMCK
A special mode is available that allows the clock that is being input through the OMCK pin to be output
through the RMCK pin. This feature is controlled by the SWCLK bit in register 4 of the control registers.
When the PLL loses lock, the frequency of the VCO drops to 300 kHz. The SWCLK function allows the
clock from RMCK to be used as a clock in the system without any disruption when input is removed from
the Receiver.
7.1.3
Error Reporting and Hold Function
While decoding the incoming AES3 data stream, the CS8420 can identify several kinds of error, indicated
in the Receiver Error register. The UNLOCK bit indicates whether the PLL is locked to the incoming AES3
data. The V bit reflects the current validity bit status. The CONF (confidence) bit indicates the amplitude
of the eye pattern opening, indicating a link that is close to generating errors. The BIP (bi-phase) error bit
indicates an error in incoming bi-phase coding. The PAR (parity) bit indicates a received parity error.
The error bits are “sticky” - they are set on the first occurrence of the associated error and will remain set
until the user reads the register via the control port. This enables the register to log all unmasked errors
that occurred since the last time the register was read.
The Receiver Error Mask register allows masking of individual errors. The bits in this register serve as
masks for the corresponding bits of the Receiver Error Register. If a mask bit is set to 1, the error is considered unmasked, meaning that its occurrence will be reported in the receiver error register, will affect
the RERR pin, will invoke the occurrence of a RERR interrupt, and will affect the current audio sample
according to the status of the HOLD bits. The HOLD bits allow a choice of holding the previous sample,
replacing the current sample with zero (mute), or do not change the current audio sample. If a mask bit is
set to 0, the error is considered masked, meaning that its occurrence will not be reported in the receiver
error register, will not induce a pulse on RERR or generate a RERR interrupt, and will not affect the current
audio sample. The QCRC and CCRC errors do not affect the current audio sample, even if unmasked.
22
DS245F4
CS8420
7.1.4
Channel Status Data Handling
The first 2 bytes of the Channel Status block are decoded into the Receiver Channel Status register. The
setting of the CHS bit in the Channel Status Data Buffer Control register determines whether the channel
status decodes are from the A channel (CHS = 0) or B channel (CHS = 1).
The PRO (professional) bit is extracted directly. Also, for consumer data, the COPY (copyright) bit is extracted, and the category code and L bits are decoded to determine SCMS status, indicated by the ORIG
(original) bit. Finally, the AUDIO bit is extracted, and used to set an AUDIO indicator, as described in the
Non-Audio Auto Detection section below.
If 50/15 µs pre-emphasis is detected, then this is reflected in the state of the EMPH pin.
The encoded sample word length channel status bits are decoded according to AES3-1992 or IEC 60958.
If the AES3 receiver is the data source for the SRC, then the SRC audio input data is truncated according
to the channel status word length settings. Audio data routed to the serial audio output port is unaffected
by the word length settings; all 24 bits are passed on as received.
“Channel Status and User Data Buffer Management” on page 81 describes the overall handling of CS and
U data.
7.1.5
User Data Handling
The incoming user data is buffered in a user-accessible buffer. Various automatic modes of re-transmitting received U data are provided. “Channel Status and User Data Buffer Management” on page 81 describes the overall handling of CS and U data.
Received U data may also be output to the U pin, under the control of a control register bit. Depending on
the data flow and clocking options selected, there may not be a clock available to qualify the U data output.
Figure 19 illustrates the timing.
If the incoming user data bits have been encoded as Q-channel subcode, the data is decoded and presented in 10 consecutive register locations. An interrupt may be enabled to indicate the decoding of a new
Q-channel block, which may be read via the control port.
RCBL
out
VLRCK
C, U
Output
RCBL and C output are only available in hardware mode 5.
RCBL goes high 2 frames after receipt of a Z pre-amble, and is high for 16 frames.
VLRCK is a virtual word clock, which may not exist, but is used to illustrate the CU timing.
VLRCK duty cycle is 50%. VLRCK frequency is always equal to the incoming frame rate.
If no SRC is used, and the serial audio output port is in master mode, VLRCK = OLRCK.
If the serial audio output port is in slave mode, then VLRCK needs to be externally created, if required.
C, U transitions are aligned within ±1% of VLRCK period to VLRCK edges
Figure 19. AES3 Receiver Timing for C & U Pin Output Data
DS245F4
23
CS8420
7.1.6
Non-Audio Auto Detection
Since it is possible to convey non-audio data in an AES3 data stream, it is important to know whether the
incoming AES3 data stream is digital audio or other data. This information is typically conveyed in channel
status bit 1 (AUDIO), which is extracted automatically by the CS8420. However, certain non-audio sources, such as AC-3® or MPEG encoders, may not adhere to this convention, and the bit may not be properly
set. The CS8420 AES3 receiver can detect such non-audio data. This is accomplished by looking for a
96-bit sync code, consisting of 0x0000, 0x0000, 0x0000, 0x0000, 0xF872, and 0x4E1F. When the sync
code is detected, an internal AUTODETECT signal will be asserted. If no additional sync codes are detected within the next 4096 frames, AUTODETECT will be de-asserted until another sync code is detected. The AUDIO bit in the Receiver Channel Status register is the logical OR of AUTODETECT and the
received channel status bit 1. If non-audio data is detected, the data is still processed exactly as if it were
normal audio. It is up to the user to mute the outputs as required.
7.2
AES3 Transmitter
The AES3 transmitter encodes and transmits audio and digital data according to the AES3, IEC60958
(S/PDIF), and EIAJ CP-1201 interface standards. Audio and control data are multiplexed together and
bi-phase mark-encoded. The resulting bit stream is then driven directly, or through a transformer, to an
output connector.
The transmitter is usually clocked from the output side clock domain of the sample rate converter. This
clock may be derived from the clock input pin OMCK, or from the incoming data. In data flows with no
SRC, and where OMCK is asynchronous to the data source, an interrupt bit is provided that will go high
every time a data sample is dropped or repeated.
The channel status (C) and user channel (U) bits in the transmitted data stream are taken from storage
areas within the CS8420. The user can manipulate the contents of the internal storage with a microcontroller. The CS8420 will also run in one of several automatic modes. “Channel Status and User Data Buffer
Management” on page 81 provides detailed descriptions of each automatic mode, and describes methods
for accessing the storage areas. The transmitted user data can optionally be input via the U pin, under the
control of a control port register bit. Figure 20 shows the timing requirements for inputting U data via the
U pin.
7.2.1
Transmitted Frame and Channel Status Boundary Timing
The TCBL pin may be an input or an output, and is used to control or indicate the start of transmitted channel status block boundaries.
In some applications, it may be necessary to control the precise timing of the transmitted AES3 frame
boundaries. This may be achieved in 3 ways:
1) With TCBL configured as an input, and TCBL transitions high for >3 OMCK clocks, it will cause a frame
start, and a new channel status block start.
2) If the AES3 output comes from the AES3 input, while there is no SRC, setting TCBL as output will cause
AES3 output frame boundaries to align with AES3 input frame boundaries.
3) If the AES3 output comes from the serial audio input port while the port is in Slave mode, and TCBL is
set to output, then the start of the A channel sub-frame will be aligned with the leading edge of ILRCK.
24
DS245F4
CS8420
7.2.2
TXN and TXP Drivers
The line drivers are low-skew, low-impedance, differential outputs capable of driving cables directly. Both
drivers are set to ground during reset (RST = low), when no AES3 transmit clock is provided, and optionally under the control of a register bit. The CS8420 also allows immediate mute of the AES3 transmitter
audio data via a control register bit.
External components are used to terminate and isolate the external cable from the CS8420. These components are detailed in “External AES3/SPDIF/IEC60958 Transmitter and Receiver Components” on
page 78.
7.3
Mono Mode Operation
Currently, the AES3 standard is being updated to include options for 96-kHz sample rate operation. One
method is to double the frame rate of the current format. This results in a
96-kHz sample rate, stereo signal carried over a single twisted pair cable. An alternate method is where the
2 sub-frames in a 48-kHz frame rate AES3 signal are used to carry consecutive samples of a mono signal,
resulting in a 96-kHz sample rate stream. This allows older equipment, whose AES3 transmitters and receivers are not rated for 96-kHz frame rate operation, to handle 96-kHz sample rate information. In this
“mono mode”, 2 AES3 cables are needed for stereo data transfer. The CS8420 offers mono mode operation, both for the AES3 receiver and for the AES3 transmitter. Figure 21 shows the operation of mono mode
in comparison with normal stereo mode. The receiver and transmitter sections may be independently set to
mono mode via the MMR and MMT control bits.
The receiver mono mode effectively doubles Fsi compared to the input frame rate. The clock output on the
RMCK pin tracks Fsi, and so is doubled in frequency compared to stereo mode. In mono mode, A and B
sub-frames are routed to the SRC inputs as consecutive samples.
When the transmitter is in mono mode, either A or B SRC consecutive outputs are routed alternately to A
and B sub-frames in the AES3 output stream. Which channel status block is transmitted is also selectable.
For the AES3 input to serial audio port output data flow, in receiver mono mode, then the receiver will run
at a frame rate of Fsi/2, and the serial audio output port will run at Fsi. Identical data will appear in both left
and right data fields on the SDOUT pin.
For the serial audio input port to AES3 transmitter data flow, in transmitter mono mode, then the input port
will run at Fso audio sample rate, while the AES3 transmitter frame rate will be at Fso/2. The data from either
consecutive left, or right, positions will be selected for transmitting in A and B sub-frames.
DS245F4
25
CS8420
Tth
TCBL
In or Out
VLRCK
Tsetup
Thold
VCU
Input
VCU[0]
SDIN
Input
TXP(N)
Data[4]
Z
VCU[1]
Data[5]
Data[0]
Y
Data[1]
VCU[2]
Data[6]
X
Data[2]
VCU[3]
Data[7]
Y
Data[3]
AES3 Transmitter in Stereo Mode
TCBL
In or Out
Tth
VCU[4]
Data[8]
X
Data[4]
Tsetup = > 7.5 % AES3 frame time
Thold = 0
Tth > 3 OMCK if TCBL is Input
VLRCK
U
Input
U[0]
SDIN
Input
TXP(N)
Output
Data[4]
Z
Data[5]
Data[0]*
U[2]
Data[6]
Data[7]
Data[8]
Y
Data[2]*
X
Data[4]*
Y
Data[3]*
X
Data[5]*
*Assume MMTLR = 0
TXP(N)
Z
Data[1]*
Output
*Assume MMTLR = 1
AES3 Transmitter in Mono Mode
Tsetup = > 15 % AES3 frame time
Thold = 0
Tth > 3 OMCK if TCBL is Input
VLRCK is a virtual word clock, which may not exist, and is used to illustrate CUV timing.
VLRCK duty cycle is 50%
In stereo mode, VLRCK frequency = AES3 frame rate. In mono mode, ALRCK frequency = 2xAES3 frame rate.
If the serial audio input port is .in slave mode and TCBL is an output, the VLRCK=ILRCK if SILRPOL=0 and
VLRCK = ILRCK if SILRPOL = 1.
If the serial audio input port is in master mode and TCBL is an input, the VLRCK=ILRCK if SILRPOL=0 and
VLRCK= ILRCK if SILRPOL = 1.
Figure 20. AES3 Transmitter Timing for C, U and V Pin Input Data
26
DS245F4
CS8420
TRANSMITTER
STEREO MODE
RECEIVER
STEREO MODE
96kHz
Fsi
96kHz stereo
96kHz frame rate
AES3
Receiver
A
A
B
B
PLL
In
96kHz
Fso
SRC
Out
A
A
B
AES3
B Transmitter
OMCK (256, 384, or 512x 96kHz)
256x96kHz
TRANSMITTER
MONO MODE
RECEIVER
MONO MODE
96kHz
Fsi
96kHz mono
48kHz frame rate
A
AES3
Receiver
96kHz stereo
96kHz frame rate
*
B
A
In
96kHz
Fso
SRC
A
A
+
B
PLL (x2)
Out
96kHz mono
48kHz frame rate
MMTLR
B
AES3
B Transmitter
256x96kHz
OMCK (256, 384, or 512x 96kHz)
* A & B sub-frames data are time-multiplexed
into consecutive samples
+ Consecutive samples are alternately routed
to A & B sub-fames
TRANSMITTER TIMING
RECEIVER TIMING
Frame
Incoming
AES3
B1
A1
A2
B2
SRC Ain
A1
A2
SRC Bin
B1
B2
MONO
A1
A1
A2
SRC Bout
B1
B2
STEREO
STEREO
Ain & Bin
SRC
SRC Aout
B1
A2
B2
Outgoing
AES3
Outgoing
AES3
A selected
Frame
A1
B1
B2
Frame
MONO
Outgoing
AES3
B selected
A2
A1
A2
B1
B2
Figure 21. Mono Mode Operation Compared to Normal Stereo Operation
DS245F4
27
CS8420
8.
8.1
AES3 TRANSMITTER AND RECEIVER
Sample Rate Converter
The equation for the group delay through the sample rate converter, with the serial ports in Master mode is:
((input interface delay + 43) / Fsi) + ((43 + output interface delay ± 0.5) / Fso)
The unit of delay depends on the frame rate (sample rate) Fs. The AES receiver has a interface delay of 2
frames. The AES transmitter, the serial input port, and the serial output port each have an interface delay
of 1 frame. The ± 0.5 frame delay in the second half of the equation is due to the start-up uncertainty of the
logic within the part.
When using multiple parts together, it is possible to start the parts simultaneously in a fashion that minimizes
the relative group delay between the parts. When multiple parts are started together in the proper way, the
variation in signal delay through the parts is ±1.5 μs.
To start the parts simultaneously, set up each one so that the PLL will lock, with the active input port driving
both output ports. Then simultaneously enable the RUN bits in all of the parts. TCBL on one of the CS8420
parts should be set as an output, while the remaining TCBL pins should be set as inputs. This synchronizes
the AES transmitter on all of the parts.
Depending upon software considerations, it may be advantageous to configure the registers so that an interrupt is generated on the INT pin when lock occurs. The control logic should either poll the unlock bits until
all PLL’s are locked or wait for the interrupts to indicate that all are locked, depending on which approach
you’ve chosen.
When all of the PLL’s are locked, the CS8420’s should be advanced to the next state together. Drive all the
serial control ports together with the same clock and data. Change the configuration in register 03h according to Table 1 or Table 2.
Register
(HEX)
Initial Value
(HEX)
Value After Advancing to the Running
State, After the PLL’s are Locked (HEX)
01
01 or 00
01 or 00
03
95
81
04
41
41
11
10
10
Table 1. Minimizing Group Delay Through Multiple CS8420s When Locking to RXP/RXN
Register
(HEX)
Initial Value
(HEX)
Value After Advancing to the Running
State, After the PLL’s are Locked (HEX)
01
01 or 00
01 or 00
03
8A
80
04
40
40
11
10
10
Table 2. Minimizing Group Delay Through Multiple CS8420s When Locking to ILRCK
28
DS245F4
CS8420
8.2
Non-SRC Delay
The unit of delay depends on the frame rate (sample rate) Fs. The AES receiver has a interface delay of two
frames. The AES transmitter, the serial input port, and the serial output port each have an interface delay
of 1 frame. The ± 0.5 frame delay in the second half of the equation is due to the startup uncertainty of the
logic within the part.
1. All inputs are slaves and all outputs are masters, both with respect to the outside world.
2. The inputs and outputs are synchronous to one another.
Path
Delay (in units of a frame)
RX to TX
3 ± 1/128
Serial Input to TX
2 ± 1/128
RX to Serial Output
3 ± 1/128
Serial Input to Serial Output
2 ± 1/128
Table 3. Non-SRC Delay
DS245F4
29
CS8420
9.
CONTROL PORT DESCRIPTION AND TIMING
The control port is used to access the registers, allowing the CS8420 to be configured for the desired operational
modes and formats. In addition, Channel Status and User data may be read and written via the control port. The
operation of the control port may be completely asynchronous with respect to the audio sample rates. However, to
avoid potential interference problems, the control port pins should remain static if no operation is required.
The control port has two modes: SPI and I²C, with the CS8420 acting as a slave device. SPI mode is selected if
there is a high-to-low transition on the AD0/CS pin after the RST pin has been brought high. I²C mode is selected
by connecting the AD0/CS pin to VD+ or DGND, thereby permanently selecting the desired AD0 bit address state.
9.1
SPI Mode
In SPI mode, CS is the CS8420 chip select signal. CCLK is the control port bit clock (input into the CS8420
from the microcontroller), CDIN is the input data line from the microcontroller, CDOUT is the output data line
to the microcontroller. Data is clocked in on the rising edge of CCLK and out on the falling edge.
Figure 22 shows the operation of the control port in SPI mode. To write to a register, bring CS low. The first
7 bits on CDIN form the chip address and must be 0010000b. The eighth bit is a read/write indicator (R/W),
which should be low to write. The next 8 bits form the Memory Address Pointer (MAP), which is set to the
address of the register that is to be updated. The next 8 bits are the data which will be placed into the register
designated by the MAP. During writes, the CDOUT output stays in the Hi-Z state. It may be externally pulled
high or low with a 47 kΩ resistor, if desired.
CS
CCLK
C H IP
ADDRESS
C D IN
0010000
MAP
MSB
R/W
C H IP
ADDRESS
DATA
b y te 1
LSB
0010000
R/W
b y te n
High Impedance
CDOUT
MSB
LSB MSB
LSB
MAP = Memory Address Pointer, 8 bits, MSB first
Figure 22. Control Port Timing in SPI Mode
There is a MAP auto-increment capability, enabled by the INCR bit in the MAP register. If INCR is a zero,
then the MAP will stay constant for successive read or writes. If INCR is set to a 1, then the MAP will autoincrement after each byte is read or written, allowing block reads or writes of successive registers.
To read a register, the MAP has to be set to the correct address by executing a partial write cycle which
finishes (CS high) immediately after the MAP byte. The MAP auto-increment bit (INCR) may be set or not,
as desired. To begin a read, bring CS low, send out the chip address and set the read/write bit (R/W) high.
The next falling edge of CCLK will clock out the MSB of the addressed register (CDOUT will leave the highimpedance state). If the MAP auto-increment bit is set to 1, the data for successive registers will appear
consecutively.
30
DS245F4
CS8420
9.2
I²C Mode
In I²C mode, SDA is a bidirectional data line. Data is clocked into and out of the part by the clock, SCL, with
the clock to data relationship as shown in Figure 23. There is no CS pin. Each individual CS8420 is given a
unique address. Pins AD[1:0] form the two least significant bits of the chip address and should be connected
to VD+ or DGND as desired. The EMPH pin is used to set the AD2 bit, by connecting a resistor from the
EMPH pin to VD+ or to DGND. The state of the pin is sensed while the CS8420 is being reset. The upper
four bits of the 7-bit address field are fixed at 0010b. To communicate with a CS8420, the chip address field,
which is the first byte sent to the CS8420, should match 0010b followed by the settings of the EMPH, AD1,
and AD0. The eighth bit of the address is the R/W bit. If the operation is a write, the next byte is the Memory
Address Pointer (MAP) which selects the register to be read or written. If the operation is a read, the contents of the register pointed to by the MAP will be output. Setting the auto-increment bit in MAP allows successive reads or writes of consecutive registers. Each byte is separated by an acknowledge bit. The ACK
bit is output from the CS8420 after each input byte is read and is input to the CS8420 from the microcontroller after each transmitted byte.
Note 1
0010
SDA
AD2-0
R/W
Note 2
ACK
DATA7-0 ACK
Note 3
DATA7-0
ACK
SCL
Start
Notes:
1. AD2 is derived from a resistor attached to the EMPH pin
AD1, and AD0 are determined by the state of the corresponding pins.
Stop
2. If operation is a write, this byte contains the Memory Address Pointer, MAP.
3. If operation is a read, the last bit of the read should be NACK (high).
Figure 23. Control Port Timing in I²C Mode
9.3
Interrupts
The CS8420 has a comprehensive interrupt capability. The INT output pin is intended to drive the interrupt
input pin on the host microcontroller. The INT pin may be set to be active-low, active-high, or active-low with
no active pull-up transistor. This last mode is used for active-low, wired-OR hook-ups, with multiple peripherals connected to the microcontroller interrupt input pin.
Many conditions can cause an interrupt, as listed in the interrupt status register descriptions. Each source
may be masked via mask registers. In addition, each source may be set to rising-edge, falling-edge, or levelsensitive. Combined with the option of level-sensitive or edge-sensitive modes within the microcontroller,
many different set-ups are possible, depending on the needs of the equipment designer.
DS245F4
31
CS8420
10. CONTROL PORT REGISTER BIT DEFINITIONS
10.1
Memory Address Pointer (MAP)
7
INCR
6
MAP6
5
MAP5
4
MAP4
3
MAP3
2
MAP2
1
MAP1
0
MAP0
This register defaults to 01
INCR
Auto-Increment Address Control Bit
0Auto-increment address off
1Auto-increment address on
MAP6-MAP0
Register address and function list
0Reserved
1Misc. Control 1
2Misc. Control 2
3Data Flow Control
4Clock Source Control
5Serial Audio Input Port Data Format
6Serial Audio Output Port Data Format
7Interrupt Register 1 Status
8Interrupt Register 2 Status
9Interrupt Register 1 Mask
10 Interrupt Register1 Mode (MSB)
11 Interrupt Register 1 Mode (LSB)
12 Interrupt Register 2 Mask
13 Interrupt Register 2 Mode (MSB)
14 Interrupt Register 2 Mode (LSB)
15 Receiver Channel Status Bits
16 Receiver Error Status
17 Receiver Error Mask
18 Channel Status Data Buffer Control
19 User Data Buffer Control
20 to 29 - Q-channel Subcode Bytes 0 to 9
30 Sample Rate Ratio
31 Reserved
32 to 55 - C-bit or U-bit Data Buffer
56 to 126 - Reserved
127 Chip ID and version register
Reserved registers must not be written to during normal operation. Some reserved registers are used for
test modes, which can completely alter the normal operation of the CS8420.
32
DS245F4
CS8420
Addr
(HEX)
01
02
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
13
14-1D
1E
20-37
7F
Function
7
Control 1
Control 2
Data Flow Control
Clock Source Control
Serial Input Format
Serial Output Format
Interrupt 1 Status
Interrupt 2 Status
Interrupt 1 Mask
Interrupt 1 Mode (MSB)
Interrupt 1 Mode (LSB)
Interrupt 2 Mask
Interrupt 2 Mode (MSB)
Interrupt 2 Mode (LSB)
Receiver CS Data
Receiver Errors
Receiver Error Mask
CS Data Buffer Control
U Data Buffer Control
Q Sub-Code Data
Sample Rate Ratio
C or U Data Buffer
ID and Version
6
5
4
3
2
1
0
SWCLK
VSET
MUTESAO
MUTEAES
DITH
INT1
INT0
TCBLD
TRUNC
HOLD1
HOLD0
RMCKF
MMR
MMT
MMTCS
MMTLR
AMLL
TXOFF
AESBP
TXD1
TXD0
SPD1
SPD0
SRCD
0
RUN
CLK1
CLK0
OUTC
INC
RXD1
RXD0
SILRPOL
SIMS
SISF
SIRES1
SIRES0
SIJUST
SIDEL
SISPOL
SOMS
SOSF
SORES1
SORES0
SOJUST
SODEL
SOSPOL SOLRPOL
TSLIP
OSLIP
SRE
OVRGL
OVRGR
DETC
EFTC
RERR
0
0
VFIFO
REUNLOCK
DETU
EFTU
QCH
UOVW
TSLIPM OSLIPM
SREM
OVRGLM
OVRGRM DETCM
EFTCM
RERRM
TSLIP1
OSLIP1
SRE1
OVRGL1
OVRGR1
DETC1
EFTC1
RERR1
TSLIP0
OSLIP0
SRE0
OVRGL0
OVRGR0
DETC0
EFTC0
RERR0
0
0
VFIFOM
REUNLOCKM
DETUM
EFTUM
QCHM
UOVWM
0
0
VFIFO1
REUNLOCK1
DETU1
EFTU1
QCH1
UOVW1
0
0
VFIFO0
REUNLOCK0
DETU0
EFTU0
QCH0
UOVW0
AUX3
AUX2
AUX1
AUX0
PRO
AUDIO
COPY
ORIG
0
QCRC
CCRC
UNLOCK
V
CONF
BIP
PAR
0
QCRCM
CCRCM
UNLOCKM
VM
CONFM
BIPM
PARM
0
0
BSEL
CBMR
DETCI
EFTCI
CAM
CHS
0
0
0
UD
UBM1
UBM0
DETUI
EFTUI
SRR7
SRR6
SRR5
SRR4
SRR3
SRR2
SRR1
SRR0
ID3
ID2
ID1
ID0
VER3
VER2
VER1
VER0
Table 4. Summary of all Bits in the Control Register Map
DS245F4
33
CS8420
10.2
Miscellaneous Control 1 (01h)
7
SWCLK
6
VSET
5
MUTESAO
4
MUTEAES
3
DITH
2
INT1
1
INT0
0
TCBLD
SWCLK
Causes OMCK to be output through the RMCK pin when the PLL is unlocked
0 - RMCK is driven by the PLL VCO (default)
1 - OMCK is switched to output through the RMCK pin when the PLL is unlocked. Circuitry driven by the PLL is driven by OMCK.
VSET
Transmitted V bit level
0 - Transmit a 0 for the V bit, indicating that the data is valid, and is normally linear PCM audio
(default)
1 - Transmit a 1 for the V bit, indicating that the data is invalid or is not linear PCM audio data
MUTESAO
Mute control for the serial audio output port
0 - Normal output (default)
1 - Mute the serial audio output port
MUTEAES
Mute control for the AES3 transmitter output
0 - Normal output (default)
1 - Mute the AES3 transmitter output
DITH
Dither Control
0 - Triangular PDF dither applied to output data. The level of the dither is automatically adjusted
to be appropriate for the output word length selected by the SORES bits (default)
1 - No dither applied to output data.
INT[1:0]
Interrupt (INT) output pin control
00 - Active high, high output indicates an interrupt condition has occurred (default)
01 - Active low, low output indicates an interrupt condition has occurred
10 - Open drain, active low. This setting requires an external pull up resistor on the INT pin.
11 - Reserved
TCBLD
Transmit Channel Status Block pin (TCBL) direction specifier
0 - TCBL is an input (default)
1 - TCBL is an output
34
DS245F4
CS8420
10.3
Miscellaneous Control 2 (02h)
7
TRUNC
6
HOLD1
5
HOLD0
4
RMCKF
3
MMR
2
MMT
1
MMTCS
0
MMTLR
TRUNC
Determines whether the word length is set according to the incoming Channel Status data
0 - Data to the SRC is not truncated (default)
1 - Data to the SRC is set according to the AUX field in the incoming data stream
HOLD[1:0]
The HOLD bits determine how the received audio sample is affected when a receiver
error occurs.
00 - Hold the last valid audio sample (default)
01 - Replace the current audio sample with 00 (mute)
10 - Do not change the received audio sample
11 - Reserved
RMCKF
Select recovered master clock output pin frequency.
0 - RMCK is equal to 256 * Fsi (default)
1 - RMCK is equal to 128 * Fsi
MMR
Select AES3 receiver mono or stereo operation
0 - Interpret A and B subframes as two independent channels (normal stereo operation, default)
1 - Interpret A and B subframes as consecutive samples of one channel of data.This data is
duplicated to both left and right parallel outputs of the AES receiver block. The input sample
rate (Fsi) is doubled compared to MMR=0
MMT
Select AES3 transmitter mono or stereo operation
0 - Outputs left channel input into A subframe and right channel input into B subframe (normal
stereo operation, default).
1 - Output either left or right channel inputs into consecutive subframe outputs (mono mode, left
or right is determined by MMTLR bit)
MMTCS
Select A or B channel status data to transmit in mono mode
0 - Use channel A CS data for the A sub-frame slot and use channel B CS data for the B subframe slot (default)
1 - Use the same CS data for both the A and B sub-frame output slots. If MMTLR = 0, use the
left channel CS data. If MMTLR = 1, use the right channel CS data.
MMTLR
Channel Selection for AES Transmitter mono mode
0 - Use left channel input data for consecutive sub-frame outputs (default)
1 - Use right channel input data for consecutive sub-frame outputs
DS245F4
35
CS8420
10.4
Data Flow Control (03h)
7
AMLL
6
TXOFF
5
AESBP
4
TXD1
3
TXD0
2
SPD1
1
SPD0
0
SRCD
The Data Flow Control register configures the flow of audio data to/from the following blocks:
Serial Audio Input Port, Serial Audio Output Port, AES3 receiver, AES3 transmitter, and Sample
Rate Converter. In conjunction with the Clock Source Control register, multiple Receiver/Transmitter/Transceiver modes may be selected. The output data should be muted prior to changing
bits in this register to avoid transients.
AMLL
Auto Mutes the SRC data sink when Receiver lock is lost, zero data is transmitted. The SRC
data sink may be either, or both, the Transmitter and the Serial Audio Output Port.
0 - Disables Auto Mute on loss of lock (default)
1 - Enables Auto Mute on loss of lock
TXOFF
AES3 Transmitter Output Driver Control
0 - AES3 transmitter output pin drivers normal operation (default)
1 - AES3 transmitter output pin drivers drive to 0 V.
AESBP
AES3 bypass mode selection
0 - normal operation
1 - Connect the AES3 transmitter driver input directly to the RXP pin, which become a normal
TTL threshold digital input.
TXD[1:0]
AES3 Transmitter Data Source
00 - SRC output (default)
01 - Serial audio input port
10 - AES3 receiver
11 - Reserved
SPD[1:0]
Serial Audio Output Port Data Source
00 - SRC output (default)
01 - Serial Audio Input Port
10 - AES3 receiver
11 - Reserved
SRCD
Input Data Source for SRC
0 - Serial Audio Input Port (default)
1 - AES3 Receiver
36
DS245F4
CS8420
10.5
Clock Source Control (04h)
7
0
6
RUN
5
CLK1
4
CLK0
3
OUTC
2
INC
1
RXD1
0
RXD0
This register configures the clock sources of various blocks. In conjunction with the Data Flow
Control register, various Receiver/Transmitter/Transceiver modes may be selected.
RUN
The RUN bit controls the internal clocks, allowing the CS8420 to be placed in a
“powered down”, low current consumption, state.
0 - Internal clocks are stopped. Internal state machines are reset. The fully static
control port is operational, allowing registers to be read or changed. Reading and
writing the U and C data buffers is not possible. Power consumption is low (default).
1 - Normal part operation. This bit must be written to the 1 state to allow the CS8420
to begin operation. All input clocks should be stable in frequency and phase when
RUN is set to 1.
CLK[1:0]
Output side master clock input (OMCK) frequency to output sample rate (Fso) ratio selector. If
these bits are changed during normal operation, then always stop the CS8420 first (RUN = 0),
then write the new value, then start the CS8420 (RUN = 1).
00 - OMCK frequency is 256*Fso(default)
01 - OMCK frequency is 384*Fso
10 - OMCK frequency is 512*Fso
11 - reserved
OUTC
Output Time Base
0 - OMCK input pin (modified by the selected divide ratio bits CLK1 & CLK0,
(default)
1 - Recovered Input Clock
INC
Input Time Base Clock Source
0 - Recovered Input Clock (default)
1 - OMCK input pin (modified by the selected divide ratio bits CLK1 & CLK0)
RXD[1:0]
Recovered Input Clock Source
00 - 256*Fsi, where Fsi is derived from the ILRCK pin (only possible when the
serial audio input port is in Slave mode, default)
01 - 256*Fsi, where Fsi is derived from the AES3 input frame rate
10 - Bypass the PLL and apply an external 256*Fsi clock via the RMCK pin. The AES3
receiver is held in synchronous reset. This setting is useful to prevent UNLOCK
interrupts when using an external RMCK and inputting data via the serial audio
input port.
11 - Reserved
DS245F4
37
CS8420
10.6
Serial Audio Input Port Data Format (05h)
7
SIMS
6
SISF
5
SIRES1
4
SIRES0
3
SIJUST
2
SIDEL
1
SISPOL
0
SILRPOL
SIMS
Master/Slave Mode Selector
0 - Serial audio input port is in Slave mode (default)
1 - Serial audio input port is in Master mode
SISF
ISCLK frequency (for Master mode)
0 - 64*Fsi (default)
1 - 128*Fsi
SIRES[1:0]
Resolution of the input data, for right-justified formats
00 - 24 bit resolution (default)
01 - 20 bit resolution
10 - 16 bit resolution
11 - Reserved
SIJUST
Justification of SDIN data relative to ILRCK
0 - Left-Justified (default)
1 - Right-Justified
SIDEL
Delay of SDIN data relative to ILRCK, for left-justified data formats
0 - MSB of SDIN data occurs in the first ISCLK period after the ILRCK edge (default)
1 - MSB of SDIN data occurs in the second ISCLK period after the ILRCK edge
SISPOL
ISCLK clock polarity
0 - SDIN sampled on rising edges of ISCLK (default)
1 - SDIN sampled on falling edges of ISCLK
SILRPOL
ILRCK clock polarity
0 - SDIN data is for the left channel when ILRCK is high (default)
1 - SDIN data is for the right channel when ILRCK is high
38
DS245F4
CS8420
10.7
Serial Audio Output Port Data Format (06h)
7
SOMS
6
SOSF
5
SORES1
4
SORES0
3
SOJUST
2
SODEL
1
SOSPOL
0
SOLRPOL
SOMS
Master/Slave Mode Selector
0 - Serial audio output port is in Slave mode (default)
1 - Serial audio output port is in Master mode
SOSF
OSCLK frequency (for Master mode)
0 - 64*Fso (default)
1 - 128*Fso
SORES[1:0]
Resolution of the output data on SDOUT and AES3 output when the sample rate converter is
set as the source
00 - 24 bit resolution (default)
01 - 20 bit resolution
10 - 16 bit resolution
11 - Direct copy of the received NRZ data from the AES3 receiver (including C, U, and
V bits, the time slot normally occupied by the P bit is used to indicate the location
of the block start, SDOUT pin only, serial audio output port clock must be derived
from the AES3 receiver recovered clock)
SOJUST
Justification of SDOUT data relative to OLRCK
0 - Left-Justified (default)
1 - Right-Justified (Master mode only)
SODEL
Delay of SDOUT data relative to OLRCK, for left-justified data formats
0 - MSB of SDOUT data occurs in the first OSCLK period after the OLRCK edge
(default)
1 - MSB of SDOUT data occurs in the second OSCLK period after the OLRCK edge
SOSPOL
OSCLK clock polarity
0 - SDOUT transitions occur on falling edges of OSCLK (default)
1 - SDOUT transitions occur on rising edges of OSCLK
SOLRPOL
OLRCK clock polarity
0 - SDOUT data is for the left channel when OLRCK is high (default)
1 - SDOUT data is for the right channel when OLRCK is high
DS245F4
39
CS8420
10.8
Interrupt 1 Register Status (07h) (Read Only)
7
TSLIP
6
OSLIP
5
SRE
4
OVRGL
3
OVRGR
2
DETC
1
EFTC
0
RERR
For all bits in this register, a “1” means the associated interrupt condition has occurred at least
once since the register was last read. A”0” means the associated interrupt condition has NOT
occurred since the last reading of the register. Reading the register resets all bits to 0, unless
the interrupt mode is set to level and the interrupt source is still true. Status bits that are masked
off in the associated mask register will always be “0” in this register. This register defaults to 00.
TSLIP
AES3 transmitter source data slip interrupt. In data flows with no SRC, and where OMCK, which
clocks the AES3 transmitter, is asynchronous to the data source, this bit will go high every time
a data sample is dropped or repeated. Also, when TCBL is an input, and when the SRC is not
in use, this bit will go high on receipt of a new TCBL signal.
OSLIP
Serial audio output port data slip interrupt. When the serial audio output port is in Slave mode,
and OLRCK is asynchronous to the port data source, this bit will go high every time a data sample is dropped or repeated. Also, when the SRC is used, and the SRC output goes to the output
serial port configured in Slave mode, this bit will indicate if the ratio of OMCK frequency to OLRCK frequency does not match what is set in the CLK1 and CLK0 bits.
SRE
Sample rate range exceeded indicator. Occurs if Fsi/Fso or Fso/Fsi exceeds 3.
OVRGL
Over-range indicator for left (A) channel SRC output. Occurs on internal over-range for left
channel data. Note that the CS8420 automatically clips over-ranges to plus or minus full scale.
OVRGR
Over-range indicator for right (B) channel SRC output. Occurs on internal over-range for right
channel data. Note that the CS8420 automatically clips over-ranges to plus or minus full scale
DETC
D to E C-buffer transfer interrupt. The source for this bit is true during the D to E buffer transfer
in the C bit buffer management process.
EFTC
E to F C-buffer transfer interrupt. The source for this bit is true during the E to F buffer transfer
in the C bit buffer management process.
RERR
A receiver error has occurred. The Receiver Error register may be read to determine the nature
of the error which caused the interrupt.
40
DS245F4
CS8420
10.9
Interrupt Register 2 Status (08h) (Read Only)
7
6
5
4
3
2
1
0
0
0
VFIFO
REUNLOCK
DETU
EFTU
QCH
UOVW
For all bits in this register, a “1” means the associated interrupt condition has occurred at least
once since the register was last read. A”0” means the associated interrupt condition has NOT
occurred since the last reading of the register. Reading the register resets all bits to 0, unless
the interrupt mode is set to level and the interrupt source is still true. Status bits that are masked
off in the associated mask register will always be “0” in this register. This register defaults to 00.
VFIFO
Varispeed FIFO overflow indicator. Occurs if the data buffer in the SRC overflows. This will occur if the input sample rate slows too fast.
REUNLOCK
Sample rate converter unlock indicator. This interrupt occurs if the SRC is still tracking a changing input or output sample rate.
DETU
D to E U-buffer transfer interrupt. The source of this bit is true during the D to E buffer transfer
in the U bit buffer management process (block mode only).
EFTU
E to F U-buffer transfer interrupt. The source of this bit is true during the E to F buffer transfer
in the U bit buffer management process (block mode only).
QCH
A new block of Q-subcode data is available for reading. The data must be completely read within 588 AES3 frames after the interrupt occurs to avoid corruption of the data by the next block.
UOVW
U-bit FIFO Overwrite. This interrupt occurs on an overwrite in the U-bit FIFO.
10.10 Interrupt 1 Register Mask (09h)
7
TSLIPM
6
OSLIPM
5
SREM
4
OVRGLM
3
OVRGRM
2
DETCM
1
EFTCM
0
RERRM
The bits of this register serve as a mask for the Interrupt 1 Register. If a mask bit is set to 1, the error is
considered unmasked, meaning that its occurrence will affect the INT pin and the status register. If a mask
bit is set to 0, the error is considered masked, meaning that its occurrence will not affect the INT pin or the
status register. The bit positions align with the corresponding bits in Interrupt Register 1. This register defaults to 00.
10.11 Interrupt Register 1 Mode Registers MSB & LSB (0Ah,0Bh)
7
TSLIP1
TSLIP0
6
OSLIP1
OSLIP0
5
SRE1
SRE0
4
OVRGL1
OVRGL0
3
OVRGR1
OVRGR0
2
DETC1
DETC0
1
EFTC1
EFTC0
0
RERR1
RERR0
The two Interrupt Mode registers form a 2-bit code for each Interrupt Register 1 function. This code determines whether the INT pin is set active on the arrival of the interrupt condition, on the removal of the interrupt
condition, or on the continuing occurrence of the interrupt condition. These registers default to 00.
00 - Rising edge active
01 - Falling edge active
10 - Level active
11 - Reserved
DS245F4
41
CS8420
10.12 Interrupt 2 Register Mask (0Ch)
7
0
6
0
5
VFIFOM
4
REUNLOCKM
3
DETUM
2
EFTUM
1
QCHM
0
UOVWM
The bits of this register serve as a mask for the Interrupt 2 Register. If a mask bit is set to 1, the error is
considered unmasked, meaning that its occurrence will affect the INT pin and the status register. If a mask
bit is set to 0, the error is considered masked, meaning that its occurrence will not affect the INT pin or the
status register. The bit positions align with the corresponding bits in Interrupt Register 2. This register defaults to 00.
10.13 Interrupt Register 2 Mode Registers MSB & LSB (0Dh,0Eh)
7
0
0
6
0
0
5
VFIFO1
VFIFO0
4
REUNLOCK1
REUNLOCK0
3
DETU1
DETU0
2
EFTU1
EFTU0
1
QCH1
QCH0
0
UOVW1
UOVW0
The two Interrupt mode registers form a 2-bit code for each Interrupt 2 register function. This code determines whether the INT pin is set active on the arrival of the interrupt condition, on the removal of the interrupt
condition, or on the continuing occurrence of the interrupt condition. These registers default to 00.
00 - Rising edge active
01 - Falling edge active
10 - Level active
11 - Reserved
42
DS245F4
CS8420
10.14 Receiver Channel Status (0Fh) (Read Only)
7
AUX3
6
AUX2
5
AUX1
4
AUX0
3
PRO
2
AUDIO
1
COPY
0
ORIG
The bits in this register can be associated with either channel A or B of the received data. The
desired channel is selected with the CHS bit of the Channel Status Data Buffer Control Register.
AUX[3:0]
The AUX3-0 bits indicate the width of the incoming auxiliary data field, as indicated by the incoming channel status bits, decoded according to IEC60958 and AES3.
0000 - Auxiliary data is not present
0001 - Auxiliary data is 1 bit long
0010 - Auxiliary data is 2 bits long
0011 - Auxiliary data is 3 bits long
0100 - Auxiliary data is 4 bits long
0101 - Auxiliary data is 5 bits long
0110 - Auxiliary data is 6 bits long
0111 - Auxiliary data is 7 bits long
1000 - Auxiliary data is 8 bits long
1001 - 1111 Reserved
PRO
Channel status block format indicator
0 - Received channel status block is in consumer format
1 - Received channel status block is in professional format
AUDIO
Audio indicator
0 - Received data is linearly coded PCM audio
1 - Received data is not linearly coded PCM audio
COPY
SCMS copyright indicator
0 - Copyright asserted
1 - Copyright not asserted
ORIG
SCMS generation indicator. This is decoded from the category code and the L bit.
0 - Received data is 1st generation or higher
1 - Received data is original
Note:
COPY and ORIG will both be set to 1 if the incoming data is flagged as professional or if the receiver is not
in use.
DS245F4
43
CS8420
10.15 Receiver Error (10h) (Read Only)
7
0
6
QCRC
5
CCRC
4
UNLOCK
3
V
2
CONF
1
BIP
0
PAR
This register contains the AES3 receiver and PLL status bits. Unmasked bits will go high on
occurrence of the error, and will stay high until the register is read. Reading the register resets
all bits to 0, unless the error source is still true. Bits that are masked off in the receiver error
mask register will always be 0 in this register. This register defaults to 00.
QCRC
Q-subcode data CRC error has occurred. Updated on Q-subcode block boundaries.
0 - No error
1 - Error
CCRC
Channel Status Block Cyclic Redundancy Check bit. Updated on CS block boundaries.
This bit is valid in Professional mode only.
0 - No error
1 - Error
UNLOCK
PLL lock status bit. Updated on CS block boundaries.
0 - PLL locked
1 - PLL out of lock
V
Received AES3 Validity bit status. Updated on sub-frame boundaries.
0 - Data is valid and is normally linear coded PCM audio
1 - Data is invalid, or may be valid compressed audio
CONF
Confidence bit. Updated on sub-frame boundaries.
0 - No error
1 - Confidence error. This indicates that the received data eye opening is less than
half a bit period, indicating a poor link that is not meeting specifications.
BIP
Bi-phase error bit. Updated on sub-frame boundaries.
0 - No error
1 - Bi-phase error. This indicates an error in the received bi-phase coding.
PAR
Parity bit. Updated on sub-frame boundaries.
0 - No error
1 - Parity error
44
DS245F4
CS8420
10.16 Receiver Error Mask (11h)
7
0
6
QCRCM
5
CCRCM
4
UNLOCKM
3
VM
2
CONFM
1
BIPM
0
PARM
The bits in this register serve as masks for the corresponding bits of the Receiver Error Register. If a mask bit is set to 1, the error is considered unmasked, meaning that its occurrence will
appear in the receiver error register, will affect the RERR pin, will affect the RERR interrupt, and
will affect the current audio sample according to the status of the HOLD bit. If a mask bit is set
to 0, the error is considered masked, meaning that its occurrence will not appear in the receiver
error register, will not affect the RERR pin, will not affect the RERR interrupt, and will not affect
the current audio sample. The CCRC and QCRC bits behave differently from the other bits: they
do not affect the current audio sample even when unmasked. This register defaults to 00.
10.17 Channel Status Data Buffer Control (12h)
7
0
6
0
5
BSEL
4
CBMR
3
DETCI
2
EFTCI
1
CAM
0
CHS
BSEL
Selects the data buffer register addresses to contain User data or Channel Status data
0 - Data buffer address space contains Channel Status data (default)
1 - Data buffer address space contains User data
CBMR
Control for the first 5 bytes of channel status “E” buffer
0 - Allow D to E buffer transfers to overwrite the first 5 bytes of channel status data
(default)
1 - Prevent D to E buffer transfers from overwriting first 5 bytes of channel status data
DETCI
D to E C-data buffer transfer inhibit bit.
0 - Allow C-data D to E buffer transfers (default)
1 - Inhibit C-data D to E buffer transfers
EFTCI
E to F C-data buffer transfer inhibit bit.
0 - Allow C-data E to F buffer transfers (default)
1 - Inhibit C-data E to F buffer transfers
CAM
C-data buffer control port access mode bit
0 - One byte mode
1 - Two byte mode
CHS
Channel select bit
0 - Channel A information is displayed at the EMPH pin and in the receiver channel
status register. Channel A information is output during control port reads when
CAM is set to 0 (One Byte Mode)
1 - Channel B information is displayed at the EMPH pin and in the receiver channel
status register. Channel B information is output during control port reads when
CAM is set to 0 (One Byte Mode)
DS245F4
45
CS8420
10.18 User Data Buffer Control (13h)
7
0
6
0
5
0
4
UD
3
UBM1
2
UBM0
1
DETUI
0
EFTUI
UD
User data pin (U) direction specifier
0 - The U pin is an input. The U data is latched in on both rising and falling edges of
OLRCK. This setting also chooses the U pin as the source for transmitted
U data (default).
1 - The U pin is an output. The received U data is clocked out on both rising and falling edges
of ILRCK. This setting also chooses the U data buffer as the source of transmitted
U data.
UBM[1:0]
Sets the operating mode of the AES3 U bit manager
00 - Transmit all zeros mode (default)
01 - Block mode
10 - Reserved
11 - IEC consumer mode B
DETUI
D to E U-data buffer transfer inhibit bit (valid in block mode only).
0 - Allow U-data D to E buffer transfers (default)
1 - Inhibit U-data D to E buffer transfers
EFTUI
E to F U-data buffer transfer inhibit bit (valid in block mode only).
0 - Allow U-data E to F buffer transfers (default)
1 - Inhibit U-data E to F buffer transfer
Q-Channel Subcode Bytes 0 to 9 (14h - 1Dh) (Read Only)
The following 10 registers contain the decoded Q-channel subcode data
7
6
5
4
3
2
1
0
CONTROL
CONTROL
CONTROL
CONTROL
ADDRESS
ADDRESS
ADDRESS
ADDRESS
TRACK
TRACK
TRACK
TRACK
TRACK
TRACK
TRACK
TRACK
INDEX
INDEX
INDEX
INDEX
INDEX
INDEX
INDEX
INDEX
MINUTE
MINUTE
MINUTE
MINUTE
MINUTE
MINUTE
MINUTE
MINUTE
SECOND
SECOND
SECOND
SECOND
SECOND
SECOND
SECOND
SECOND
FRAME
FRAME
FRAME
FRAME
FRAME
FRAME
FRAME
FRAME
ZERO
ZERO
ZERO
ZERO
ZERO
ZERO
ZERO
ZERO
ABS MINUTE ABS MINUTE ABS MINUTE ABS MINUTE ABS MINUTE ABS MINUTE ABS MINUTE ABS MINUTE
ABS SECOND ABS SECOND ABS SECOND ABS SECOND ABS SECOND ABS SECOND ABS SECOND ABS SECOND
ABS FRAME ABS FRAME ABS FRAME ABS FRAME ABS FRAME ABS FRAME ABS FRAME ABS FRAME
Each byte is LSB first with respect to the 80 Q-subcode bits Q[79:0]. Thus bit 7 of address 14h is Q[0] while
bit 0 of address 14h is Q[7]. Similarly bit 0 of address 1Dh corresponds to Q[79].
46
DS245F4
CS8420
10.19 Sample Rate Ratio (1Eh) (Read Only)
7
SRR7
6
SRR6
5
SRR5
4
SRR4
3
SRR3
2
SRR2
1
SRR1
0
SRR0
The Sample Rate Ratio is Fso divided by Fsi. This value is represented as an integer and a
fractional part. The value is meaningful only after the both the PLL and SRC have reached lock,
and the SRC output is being used
SRR[7:6
The integer part of the sample rate ratio
SRR[5:0]
The fractional part of the sample rate ratio
10.20 C-Bit or U-Bit Data Buffer (20h - 37h)
Either channel status data buffer E or user data buffer E (provided UBM bits are set to block mode) is accessible via these register addresses.
10.21 CS8420 I.D. and Version Register (7Fh) (Read Only)
7
ID3
6
ID2
5
ID1
4
ID0
3
VER3
ID[3:0]
ID code for the CS8420. Permanently set to 0001
VER[3:0]
CS8420 Revision Level:
Revision B is coded as 0001
Revision C is coded as 0011
Revision D is coded as 0100
DS245F4
2
VER2
1
VER1
ID3
VER0
47
CS8420
11. SYSTEM AND APPLICATIONS ISSUES
11.1
Reset, Power Down and Start-up Options
When RST is low, the CS8420 enters a low-power mode. All internal states are reset, including the control
port and registers, and the outputs are muted. When RST is high, the control port becomes operational, and
the desired settings should be loaded into the control registers. Writing a 1 to the RUN bit will then cause
the part to leave the low-power state and begin operation. After the PLL and the SRC have settled, the AES3
and serial audio outputs will be enabled.
Some options within the CS8420 are controlled by a start-up mechanism. During the reset state, some of
the output pins are reconfigured internally to be inputs. Immediately upon exiting the reset state, the level
of these pins is sensed. The pins are then switched to be outputs. This mechanism allows output pins to be
used to set alternative modes in the CS8420 by connecting a 47 kΩ resistor between the pin and either VD+
(High) or DGND (Low). For each mode, every start-up option select pin MUST have an external pull-up or
pull-down resistor. In software mode, the only start-up option pin is EMPH, which is used to set a chip address bit for the control port in I²C mode. Hardware modes use many start-up options, which are detailed in
the hardware definition section at the end of this data sheet.
11.2
Transmitter Startup
When the CS8420 is taken out of power-down and the AES3 receiver is configured to be in-circuit, the part
uses the clock recovered from the AES3 input stream to advance its internal state machine to run. This can
be a problem if no valid AES3 stream is present at the RXP/RXN pins and data input through the serial audio
port needs to be output through the AES3 transmitter.
To complete initialization and begin operation when the AES3 receiver is in-circuit and no valid AES3 input
stream is presented to the RXP/RXN pins, the user must execute the following sequence:
1. Place the CS8420 in power-down (RUN = 0).
2. Set the serial audio input and output ports to Slave mode (SIMS = 0, SOMS = 0).
3. Set the input and output time base to the OMCK input pin (OUTC = 0, INC = 1).
4. Configure the SRC to receive its input from the serial audio input port (SRCD = 0).
5. Configure the serial audio output port to receive its input from the serial audio input port (SPD[1:0] = 01).
6. Configure the AES3 transmitter to receive its input from the serial audio input port (TXD[1:0] = 01).
7. Set the RUN bit (RUN = 1).
After completing steps 1-7, the transmitter will function properly, and the data flow can be altered for the
application without powering down.
48
DS245F4
CS8420
11.3
SRC Invalid State
Occasionally the CS8420 SRC will enter an invalid state. This can happen after the RUN bit has been set
when an AES3 stream is first plugged into the part or when a source device interrupts the SRC input stream.
When this happens, two symptoms may be noticeable: notches occurring in the frequency response and
spurious tones being generated in response to some input frequencies.
To avoid this problem in Software mode, use the microcontroller to monitor the UNLOCK bit in control register 10h. When the part achieves lock, clear the RUN bit in register 4 and then set it again. This will reset
all internal state machines. Alternately, the user may use the following sequence:
1. Power on CS8420.
2. Write the following register sequence:
Register
Value
04h
09h
03h
95h
04h
49h
3. Wait for PLL to lock.
4. Wait 250ms for SRC to lock.
5. Write the following register sequence:
Register
Value
03h
81h
04h
41h
6. If PLL goes out of lock, start at step 2 and repeat.
When synchronizing multiple CS8420s, wait for all PLLs to lock before continuing to the next step. These
actions clear the invalid state if it has occurred.
In Hardware mode, monitor the RERR pin for receiver lock status. When the part achieves lock, set the RST
pin low for at least 200 μs and then set it high again. This action clears the invalid state if it has occurred.
When polling the RERR pin again, the user must account for the fact that the RERR pin will be high during
reset and remain high until the PLL has reachieved lock.
In either Software or Hardware mode, when clearing the invalid state, it is advisable to mute any devices
connected to the output of the CS8420.
11.4
C/U Buffer Data Corruption
Occasionally the C/U buffer data may be corrupted. This can happen after the RUN bit has been set and
data has been written to the C/U buffer (20h-37h). If no further data is written to the C buffer after the initial
write and the receiver input is interrupted multiple times, the contents of the buffer may be reset to all zeros.
The buffer will not be corrupted if the buffer data is being updated, only when the data is static and the receiver input has been interrupted multiple times.
To avoid this problem in Software mode when the C/U buffer contents should remain static, use the microcontroller to monitor the UNLOCK bit in control register 10h or the RERR pin. If the part indicates the PLL
has lost lock, rewrite the C/U buffer data. Repeat this action every time the PLL goes out of lock.
In Hardware mode, this limitation does not exist as the serial C/U data is being fed directly to the transmitter.
DS245F4
49
CS8420
11.5
Block-Mode U-Data D-to-E Buffer Transfers
When Fsi ≠ Fso, Block-Mode U-data transfers from the D buffer to the E buffer are not synchronous to the
input clock domain. D-to-E buffer transfers can always be detected by the activation of the DETU bit (bit 3
in register 08h) when Fsi ≠ Fso or Fsi = Fso. IEC Consumer B mode, serial U-data output, and the Qchannel subcode bytes (registers 14h - 1Dh) are unaffected by the input/output sample rate relationship.
11.6
ID Code and Revision Code
The CS8420 has a register that contains a 4-bit code to indicate that the addressed device is a CS8420.
This is useful when other CS84xx family members are resident in the same system, allowing common software modules.
The CS8420 4-bit revision code is also available. This allows the software driver for the CS8420 to identify
which revision of the device is in a particular system, and modify its behavior accordingly. To allow for future
revisions, it is strongly recommend that the revision code is read into a variable area within the microcontroller, and used wherever appropriate as revision details become known.
11.7
Power Supply, Grounding, and PCB layout
For most applications, the CS8420 can be operated from a single +5V supply, following normal supply decoupling practice (see Figure 5. “Recommended Connection Diagram for Software Mode” on page 12). For
applications where the recovered input clock, output on the RMCK pin, is required to be low-jitter, then use
a separate, quiet, analog +5V supply for VA+, decoupled to AGND. In addition, a separate region of analog
ground plane around the FILT, AGND, VA+, RXP and RXN pins is recommended.
The VD+ supply should be well-decoupled with a 0.1 μF capacitor to DGND to minimize AES3 transmitter
induced transients.
Extensive use of power and ground planes, ground plane fill in unused areas and surface mount decoupling
capacitors are recommended. Make sure decoupling capacitors are mounted on the same side of the board
as the CS8420, to minimize via inductance effects. All decoupling capacitors should be as close to the
CS8420 as possible.
11.8
Synchronization of Multiple CS8420s
The serial audio output ports of multiple CS8420s can be synchronized by sharing the same master clock,
OSCLK, OLRCK, and RST line and ensuring that all devices leave the reset state on the same master clock
falling edge. Either all the ports need to be in Slave mode, or one can be set as a master.
The AES3 transmitters may be synchronized by sharing the same master clock, TCBL, and RST signals,
and ensuring all devices leave the reset state on the same master clock falling edge. The TCBL pin is used
to synchronize multiple CS8420 AES3 transmitters at the channel status block boundaries. One CS8420
must have its TCBL set to master; the others must be set to slave TCBL. Alternatively, TCBL can be derived
from some external logic, in which case all the CS8420 devices should be set to slave TCBL.
11.9
Extended Range Sample Rate Conversion
For handling sampling rate conversion ratios greater than 3:1 or less than 1:3, the user can use a cascade
of two devices. The product of the conversion ratio of the two devices should equal the target conversion
ratio.
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12. SOFTWARE MODE - PIN DESCRIPTION
The above diagram and the following pin descriptions apply to Software mode. In Hardware mode, some pins
change their function as described in subsequent sections of this data sheet. Fixed function pins are marked with a
*, and will be described once in this section. Pins marked with a + are used upon reset to select various start-up
options, and require a pull-up or pull-down resistor.
Power Supply Connections:
VD+ - Positive Digital Power *
Positive supply for the digital section. Nominally +5.0 V.
VA+ - Positive Analog Power *
Positive supply for the analog section. Nominally +5.0 V. This supply should be as quiet as possible since noise on
this pin will directly affect the jitter performance of the recovered clock.
DGND - Digital Ground *
Ground for the digital section. DGND should be connected to the same ground as AGND.
AGND - Analog Ground *
Ground for the analog section. AGND should be connected to the same ground as DGND.
Clock-Related Pins:
OMCK - Output Section Master Clock Input
Output section master clock input. The frequency must be 256x, 384x, or 512x the output sample rate (Fso).
RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 128x or 256x the input sample rate (Fsi).
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CS8420
FILT - PLL Loop Filter *
An RC network should be connected between this pin and ground. Recommended schematic and component values are given in “PLL Filter” on page 87.
Overall Device Control:
H/S - Hardware or Software Control Mode Select *
The H/S pin determines the method of controlling the operation of the CS8420, and the method of accessing CS
and U data. In Software mode, device control and CS and U data access is primarily via the control port, using a
microcontroller. In Hardware mode, alternate modes and access to CS and U data is provided by pins. This pin
should be permanently tied to VD+ or DGND.
RST - Reset Input *
When RST is low, the CS8420 enters a low-power mode and all internal states are reset. On initial power-up, RST
must be held low until the power supply is stable, and all input clocks are stable in frequency and phase. This is
particularly true in Hardware mode with multiple CS8420 devices, where synchronization between devices is important.
INT - Interrupt Output
The INT output pin indicates errors and key events during the operation of the CS8420. All bits affecting INT are
maskable via control registers. The condition(s) that initiated interrupt are readable via a control register. The polarity
of the INT output, as well as selection of a standard or open-drain output, is set via a control register. Once set true,
the INT pin goes false only after the interrupt status registers have been read, and the interrupt status bits have returned to zero.
Audio Input Interface:
SDIN - Serial Audio Input Port Data Input
Audio data serial input pin.
ISCLK - Serial Audio Input Port Bit Clock Input or Output
Serial bit clock for audio data on the SDIN pin.
ILRCK - Serial Audio Input Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDIN pin. The frequency will be at the input sample rate (Fsi)
AES3/SPDIF Receiver Interface:
RXP, RXN - Differential Line Receiver Inputs
Differential line receiver inputs, carrying AES3-type data.
RERR - Receiver Error Indicator
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
sub-frame of incoming AES3 data. Conditions that can cause RERR to go high are: validity, parity error, bi-phase
coding error, confidence, QCRC and CCRC errors, as well as loss of lock in the PLL. Optionally, each condition may
be masked from affecting the RERR pin using the Receiver Error Mask Register. The RERR pin tracks the status
of the unmasked errors: the pin goes high as soon as an unmasked error occurs and goes low immediately when
all unmasked errors go away.
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EMPH - Pre-Emphasis Indicator Output
EMPH is low when the incoming AES3 data indicates the presence of 50/15 μs pre-emphasis. When the AES3 data
indicates the absence of pre-emphasis or the presence of other than 50/15 μs pre-emphasis EMPH is high. This is
also a start-up option pin, and requires a 47 kΩ resistor to either VD+ or DGND, which determines the AD2 address
bit for the control port in I²C mode.
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin.
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the output sample rate (Fso)
AES3/SPDIF Transmitter Interface:
TCBL - Transmit Channel Status Block Start
This pin can be configured as an input or output. When operated as output, TCBL is high during the first sub-frame
of a transmitted channel status block, and low at all other times. When operated as input, driving TCBL high for at
least three OMCK (or RMCK, depending on which clock is operating the AES3 encoder block) clocks will cause the
next transmitted sub-frame to be the start of a channel status block.
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
Control Port Signals:
SCL/CCLK - Control Port Clock
SCL/CCLK is the serial control interface clock, and is used to clock control data bits into and out of the CS8420.
AD0/CS - Address Bit 0 (I²C) / Control Port Chip Select (SPI)
A falling edge on this pin puts the CS8420 into SPI Control Port mode. With no falling edge, the CS8420 defaults to
I²C mode. In I²C mode, AD0 is a chip address pin. In SPI mode, CS is used to enable the control port interface on
the CS8420.
AD1/CDIN - Address Bit 1 (I²C) / Serial Control Data In (SPI)
In I²C mode, AD1 is a chip address pin. In SPI mode, CDIN is the input data line for the control port interface
SDA/CDOUT - Serial Control Data I/O (I²C) / Data Out (SPI)
In I²C mode, SDA is the control I/O data line. SDA is open drain and requires an external pull-up resistor to VD+. In
SPI mode, CDOUT is the output data from the control port interface on the CS8420.
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CS8420
Miscellaneous Pins:
U - User Data
The U pin may optionally be used to input User data for transmission by the AES3 transmitter (see Figure 20 for
timing information). Alternatively, the U pin may be set to output User data from the AES3 receiver (see Figure 19
for timing information). If not driven, a 47 kΩ pull-down resistor is recommended for the U pin since the default state
of the UD direction bit sets the U pin as an input. The pull-down resistor ensures that the transmitted user data will
be zero. If the U pin is always set to be an output, thereby causing the U bit manager to be the source of the U data,
the resistor is not necessary. The U pin should not be tied directly to ground in case it is programmed to be an output
and subsequently tries to output a logic high. This situation may affect the long-term reliability of the device. If the U
pin is driven by a logic level output, a 100 Ω series resistor is recommended.
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13. HARDWARE MODES
13.1
Overall Description
The CS8420 has six Hardware modes, which allow use of the device without using a micro-controller to access the device control registers and CS & U data. The flexibility of the CS8420 is necessarily limited in
Hardware mode. Various pins change function in Hardware mode, and various data paths are also possible.
These alternatives are identified by Hardware mode numbers 1 through 6. The following sections describe
the data flows and pin definitions for each Hardware mode.
13.1.1 Hardware Mode Definitions
Hardware mode is selected by connecting the H/S pin to ‘1’. In Hardware mode, 3 pins (DFC0, DFC1 &
S/AES) determine the Hardware mode number, according to Table 5. Start-up options are used extensively in Hardware mode. Options include whether the serial audio output ports are master or slave, the
serial audio ports’ format and whether TCBL is an input or an output. Which output pins are used to set
which modes depends on which Hardware mode is being used.
DFC1 DFC0 S/AES
0
0
0
1
1
1
0
0
1
0
1
1
0
1
0
1
Hardware Mode Number
1 - Default Data Flow, AES3 input
2 - Default Data Flow, serial input
3 - Transceive Flow, with SRC
4 - Transceive Flow, no SRC
5 - AES3 Rx only, AES3 input
6 - AES3 Tx only, serial input
Table 5. Hardware Mode Definitions
13.1.2 Serial Audio Port Formats
In Hardware mode, only a limited number of alternative serial audio port formats are available. These formats are described by Tables 6 and 7, which define the equivalent Software mode bit settings for each
format. Timing diagrams are shown in Figures 17 and 18.
For each Hardware mode, the following pages contain a data flow diagram, a pin-out drawing, a pin descriptions list and a definition of the available start-up options.
OF1 - Left-Justified
OF2 - I²S 24-bit data
OF3 - Right-Justified, Master
mode only
OF4 - I²S 16-bit data
OF5 - Direct AES3 data
SOSF
0
0
0
SORES1/0
00
00
00
SOJUST
0
0
1
SODEL
0
1
0
SOSPOL
1
0
0
SOLRPOL
0
1
0
0
0
10
11
0
0
1
0
0
1
1
0
SISPOL
1
0
0
0
SILRPOL
0
1
0
0
Table 6. Serial Audio Output Formats Available in Hardware Mode
IF1 - Left-Justified
IF2 - I²S
IF3 - Right-Justified 24-bit data
IF4 - Right-Justified 16-bit data
SISF
0
0
0
0
SIRES1/0
00
00
00
10
SIJUST
0
0
1
1
SIDEL
0
1
0
0
Table 7. Serial Audio Input Formats Available in Hardware Mode
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CS8420
13.2
Hardware Mode 1 Description (DEFAULT Data Flow, AES3 Input)
Hardware Mode 1 data flow is shown in Figure 24. Audio data is input via the AES3 receiver, and rate converted. The audio data at the new rate is then output both via the serial audio output port and via the AES3
transmitter.
The channel status data, user data and validity bit information are handled in four alternative modes: 1A and
1B, determined by a start-up resistor on the COPY pin. In mode 1A, the received PRO, COPY, ORIG, EMPH, and AUDIO channel status bits are output on pins. The transmitted channel status bits are copied from
the received channel status data, and the transmitted U and V bits are 0.
In mode 1B, only the COPY and ORIG pins are output, and reflect the received channel status data. The
transmitted channel status bits, user data and validity bits are input serially via the PRO/C, EMPH/U and
AUDIO/V pins. Figure 20 shows the timing requirements.
Start-up options are shown in Table 8, and allow choice of the serial audio output port as a master or slave,
choice of four serial audio output port formats, and the source for transmitted C, U and V data. The following
pages contain the detailed pin descriptions for Hardware mode 1.
If a validity, parity, bi-phase, or lock receiver error occurs, the current audio sample will be held.
VD+
DFC0
DFC1
H/S
S/AES
Clocked by
Input Derived Clock
RXP
Sample
Rate
Converter
AES3 Rx
&
Decoder
RXN
Clocked by
Output Clock
Output
Clock
Source
OMCK
Serial
Audio
Output
AES3
Encoder
& Tx
RERR MUTE
PRO/C
TXP
TXN
TCBLD
C & U bit Data Buffer
RMCK
OLRCK
OSCLK
SDOUT
COPY ORIG EMPH/U AUDIO/V TCBL
Power supply pins (VD+, VA+, DGND, AGND), the reset pin (RST) and the PLL filter pin (FILT)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 24. Hardware Mode 1 - Default Data Flow, AES3 Input
SDOUT
RMCK
RERR
COPY
LO
HI
-
-
-
LO
-
-
-
HI
-
LO
LO
HI
HI
LO
HI
LO
HI
Function
Serial Output Port is Slave
Serial Output Port is Master
Mode1A: C transmitted data is copied from received data, U & V = 0,
received PRO, EMPH, AUDIO are visible.
Mode 1B: CUV transmitted data is input serially on pins, received PRO,
EMPH, AUDIO are not visible
Serial Output Format OF1
Serial Output Format OF2
Serial Output Format OF3
Serial Output Format OF4
Table 8. Hardware Mode 1 Start-Up Options
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13.2.1 Pin Description - Hardware Mode 1
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, as shown in Table 5.
S/AES - Serial Audio or AES3 Input Select
S/AES is connected to ground in Hardware mode 1 in order to select the AES3 input.
MUTE - Mute Output Data Input
If MUTE is low, audio data is passed normally. If MUTE is high, both the AES3 transmitted audio data and the serial
audio output port data is set to digital zero.
OMCK - Output Section Master Clock Input
Output section master clock input. The frequency must be 256x the output sample rate (Fso).
AES3/SPDIF Receiver Interface:
RXP, RXN - Differential Line Receiver Inputs
Differential line receiver inputs, carrying AES3 type data.
RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 256x the input sample rate (Fsi). This is also
a start-up option pin and requires a pull-up or pull-down resistor.
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RERR - Receiver Error Indicator
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
sub-frame of incoming AES3 data. Conditions that cause RERR to go high are: parity error, and bi-phase coding
error, as well as loss of lock in the PLL. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
EMPH/U - Pre-Emphasis Indicator Output or U-Bit Data Input
The EMPH/U pin reflects either the state of the EMPH channel status bits in the incoming AES3 type data stream,
or is the serial U-bit input for the AES3 type transmitted data, clocked by OLRCK. When indicating emphasis,
EMPH/U is low if the incoming data indicates 50/15 μs pre-emphasis and high otherwise.
COPY - Copy Channel Status Bit Output
The COPY pin reflects the state of the COPY Channel Status bit in the incoming AES3 type data stream. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
ORIG - Original Channel Status Output
SCMS generation indicator. This is decoded from the incoming category code and the L bit. A low output indicates
that the audio data stream is 1st generation or higher. A high indicates that the audio data stream is original.
PRO/C - Professional Channel Status Bit Output or C-Bit Data Input
The PRO/C pin either reflects the state of the Professional/Consumer Channel Status bit in the incoming AES3 type
data stream, or is the serial C-bit input for the AES3 type transmitted data, clocked by OLRCK.
AUDIO/V - Audio Channel Status Bit Output or V-Bit Data Input
The AUDIO/V pin either reflects the state of the audio/non audio Channel Status bit in the incoming AES3 type data
stream, or is the V-bit data input for the AES3 type transmitted data stream, clocked by OLRCK.
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the output sample rate (Fso)
AES3/SPDIF Transmitter Interface:
TCBL - Transmit Channel Status Block Start
When operated as output, TCBL is high during the first sub-frame of a transmitted channel status block, and low at
all other times. When operated as input, driving TCBL high for at least three OMCK clocks will cause the current
transmitted sub-frame to be the start of a channel status block.
TCBLD - Transmit Channel Status Block Direction Input
Connect TCBLD to VD+ to set TCBL as an output. Connect TCBLD to DGND to set TCBL as an input.
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
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13.3
Hardware Mode 2 Description
(DEFAULT Data Flow, Serial Input)
Hardware Mode 2 data flow is shown in Figure 25. Audio data is input via the serial audio input port, and
rate converted. The audio data at the new rate is then output both via the serial audio output port and via
the AES3 transmitter.
The C, U, and V bits in the AES3 output stream may be set in two methods, selected by the CUVEN pin.
When CUVEN is low, mode 2A is selected, where COPY/C, ORIG/U, and EMPH/V pins allow selected
channel status data bits to be set. The COPY and ORIG pins are used to set the pro bit, the copy bit, and
the L bit, as shown in Table 9. In consumer mode, the transmitted category code shall be 0101100b, which
indicates sample rate converter. The transmitted U and V bits are zero.When the CUVEN pin is high, mode
2B is selected, where COPY/C, ORIG/U, and EMPH/V become serial bit inputs for C, U, and V data. This
data is clocked by both edges of OLRCK, and the channel status block start is indicated or determined by
TCBL. Figure 20 shows the timing requirements.
Audio serial port data formats are selected as shown in Tables 6, 7 and 10.
Start-up options are shown in Table 11, and allow choice of the serial audio output port as a master or slave
and whether TCBL is an input or an output. The serial audio input port is always a slave.
VD+
DFC0
DFC1
VD+
S/AES
Clocked by
Input Derived Clock
ILRCK
ISCLK
SDIN
Serial
Audio
Input
Output
Clock
Source
H/S
OMCK
Clocked by
Output Clock
Sample
Rate
Converter
Serial
Audio
Output
AES3
Encoder
& Tx
OLRCK
OSCLK
SDOUT
TXP
TXN
C & U bit Data Buffer
RMCK
LOCK SFMT1 SFMT0 COPY/C ORIG/U EMPH/V CUVEN TCBL
Power supply pins (VD+, VA+, DGND, AGND) & the reset pin (RST) and the PLL filter pin (FILT)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 25. Hardware Mode 2 - Default Data Flow, Serial Audio Input
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CS8420
COPY/C
ORIG/U
0
0
1
1
0
1
0
1
Function
PRO=0, COPY=0, L=0
PRO=0, COPY=0, L=1
PRO=0, COPY=1, L=0
PRO=1
Table 9. HW Mode 2A COPY/C and ORIG/U Pin Function
SFMT1
SFMT0
0
0
1
1
0
1
0
1
Function
Serial Input & Output Format IF1&OF1
Serial Input & Output Format IF2&OF2
Serial Input & Output Format IF3&OF3
Serial Input & Output Format IF4&OF3
Table 10. HW Mode 2 Serial Audio Port Format Selection
SDOUT
LO
HI
-
LOCK
LO
HI
Function
Serial Output Port is Slave
Serial Output Port is Master
TCBL is an input
TCBL is an output
Table 11. Hardware Mode 2 Start-Up Options
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13.3.1 Pin Description - Hardware Mode 2
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, according to Table 5.
S/AES - Serial Audio or AES3 Input Select
S/AES is connected to VD+ in Hardware mode 2, in order to select the serial audio input.
SFMT0, SFMT1 - Serial Audio Port Data Format Select Inputs
SFMT0 and SFMT1 select the serial audio input and output ports’ format. See Table 10.
OMCK - Output Section Master Clock Input
Output section master clock input. The frequency must be 256x the output sample rate (Fso).
Audio Input Interface:
SDIN - Serial Audio Input Port Data Input
Audio data serial input pin.
ISCLK - Serial Audio Input Port Bit Clock Input or Output
Serial bit clock for audio data on the SDIN pin.
ILRCK - Serial Audio Input Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDIN pin. The frequency will be at the input sample rate (Fsi)
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RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 256x the input sample rate (Fsi).
LOCK - PLL Lock Indicator Output
LOCK low indicates that the PLL is locked. This is also a start-up option pin, and requires a pull-up or pull-down
resistor.
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the output sample rate (Fso).
AES3/SPDIF Transmitter Interface:
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
TCBL - Transmit Channel Status Block Start
When operated as output, TCBL is high during the first sub-frame of a transmitted channel status block, and low at
all other times. When operated as input, driving TCBL high for at least three OMCK clocks will cause the current
transmitted sub-frame to be the start of a channel status block.
CUVEN - C, U and V bit Input Enable Mode Input
The CUVEN pin determines how the channel status data, user data and validity bit is input. When CUVEN is low,
Hardware mode 2A is selected, where the EMPH/V, COPY/C and ORIG/U pins are used to enter selected channel
status data. When CUVEN is high, hardware 2B is selected, where the EMPH/V, COPY/C and ORIG/U pins are
used to enter serial C, U and V data.
EMPH/V - Pre-Emphasis Indicator Input or V Bit Input
In mode 2A, EMPH/V low sets the 3 EMPH channel status bits to indicate 50/15 μs pre-emphasis. EMPH/V high
sets the 3 EMPH bits to 000 indicating no pre-emphasis. In mode 2B, EMPH/V low sets the V bit to indicate valid
audio. EMPH/V high sets the V-bit to indicate non-valid audio.
COPY/C - COPY Channel Status Bit Input or C Bit Input
In mode 2A, the COPY/C pin determines the state of the COPY, PRO and L Channel Status bits in the outgoing
AES3 type data stream (See Table 9). In mode 2B, COPY/C becomes the direct C bit input data pin.
ORIG/U - ORIG Channel Status Bit Input or U Bit Input
In mode 2A, the ORIG/U pin determines the state of the COPY, PRO and L Channel Status bits in the outgoing AES3
type data stream. (See Table 9). In mode 2B, ORIG/U becomes the direct U bit input data pin.
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13.4
Hardware Mode 3 Description
(Transceive Data Flow, with SRC)
Hardware Mode 3 data flow is shown in Figure 26. Audio data is input via the AES3 receiver, and rate converted. The audio data at the new rate is then output via the serial audio output port. Different audio data,
synchronous to OMCK, may be input into the serial audio input port, and output via the AES3 transmitter.
The channel status data, user data, and validity bit information are handled in two alternative modes: 3A
and 3B, determined by a start-up resistor on the COPY pin. In mode 3A, the received PRO, COPY, ORIG,
and AUDIO channel status bits are output on pins. The transmitted channel status bits are copied from the
received channel status data, and the transmitted U and V bits are zero.
In mode 3B, only the COPY, and ORIG pins are output, and reflect the received channel status data. The
transmitted channel status bits, user data, and validity bits are input serially via the PRO/C, EMPH/U, and
AUDIO/V pins. Figure 20 shows the timing requirements.
The serial audio input port is always a slave.
If a validity, parity, bi-phase, or lock receiver error occurs, the current audio sample will be held.
Start-up options are shown in Table 12, and allow choice of the serial audio output port as a master or slave,
whether TCBL is an input or an output, the serial audio ports formats, and the source of the transmitted C,
U, and V data. The following pages contain the detailed pin descriptions for Hardware mode 3.
VD+
DFC0
VD+
H/S
DFC1
Clocked by
Input Derived Clock
RXP
RXN
AES3 Rx
&
Decoder
OSCLK
ISCLK
SDOUT OLRCK ILRCK
SDIN
Clocked by
Output Clock
Serial
Audio
Output
Output
Clock
Source
OMCK
Serial
Audio
Input
Sample
Rate
Converter
AES3
Encoder
& Tx
TXP
TXN
C & U bit Data Buffer
RMCK RERR
PRO/C COPY ORIG EMPH/U AUDIO/V TCBL
Power supply pins (VD+, VA+, DGND, AGND) & the reset pin (RST) and the PLL filter pin (FILT)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 26. Hardware Mode 3 - Transceive Data Flow, with SRC
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CS8420
SDOUT RMCK RERR ORIG COPY
Function
LO
Serial Output Port is Slave
HI
Serial Output Port is Master
LO Mode 3A: C transmitted data is copied from received data, U & V =0,
received PRO, EMPH, AUDIO is visible
HI Mode 3B: CUV transmitted data is input serially on pins, received PRO,
EMPH and AUDIO is not visible
LO
LO
Serial Input & Output Format IF1&OF1
LO
HI
Serial Input & Output Format IF2&OF2
HI
LO
Serial Input & Output Format IF3&OF3
HI
HI
Serial Input & Output Format IF2&OF4
LO
TCBL is an input
HI
TCBL is an output
Table 12. Hardware Mode 3 Start-Up Options
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13.4.1 Pin Description - Hardware Mode 3
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, according to Table 5.
OMCK - Output Section Master Clock Input
Output section master clock input. The frequency must be 256x the output sample rate (Fso).
Audio Input Interface:
SDIN - Serial Audio Input Port Data Input
Audio data serial input pin. This data will be transmitted out the AES3 port.
ISCLK - Serial Audio Input Port Bit Clock Input
Serial bit clock for audio data on the SDIN pin.
ILRCK - Serial Audio Input Port Left/Right Clock Input
Word rate clock for the audio data on the SDIN pin. The frequency will be at the output sample rate (Fso)
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
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CS8420
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the output sample rate (Fso).
AES3/SPDIF Transmitter Interface:
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
TCBL - Transmit Channel Status Block Start
When operated as output, TCBL is high during the first sub-frame of a transmitted channel status block, and low at
all other times. When operated as input, driving TCBL high for at least three OMCK clocks will cause the current
transmitted sub-frame to be the start of a channel status block.
AES3/SPDIF Receiver Interface:
RXP, RXN - Differential Line Receiver Inputs
Differential line receiver inputs, carrying AES3 type data.
RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 256x the input sample rate (Fsi). This is also
a start-up option pin, and requires a pull-up or pull-down resistor.
RERR - Receiver Error Indicator Output
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
sub-frame of incoming AES3 data. Conditions that cause RERR to go high are: parity error, and bi-phase coding
error, as well as loss of lock in the PLL. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
EMPH/U - Pre-emphasis Indicator Output or U-Bit Data Input
The EMPH/U pin either reflects the state of the EMPH channel status bits in the incoming AES3 type data stream,
or is the serial U-bit input for the AES3 type transmitted data, clocked by OLRCK. If indicating emphasis EMPH/U
is low when the incoming data indicates 50/15 μs pre-emphasis and high otherwise.
COPY - Copy Channel Status Bit Output
The COPY pin reflects the state of the COPY Channel Status bit in the incoming AES3 type data stream. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
ORIG - Original Channel Status Output
SCMS generation indicator. This is decoded from the incoming category code and the L bit. A low output indicates
that the audio data stream is 1st generation or higher. A high indicates that the audio data stream is original. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
PRO/C - Professional Channel Status Bit Output or C-Bit Data Input
The PRO/C pin either reflects the state of the Professional/Consumer Channel Status bit in the incoming AES3 type
data stream, or is the serial C-bit input for the AES3 type transmitted data, clocked by OLRCK.
AUDIO/V - Audio Channel Status Bit Output or V-Bit Data Input
The AUDIO/V pin either reflects the state of the audio/non audio Channel Status bit in the incoming AES3 type data
stream, or is the V-bit data input for the AES3 type transmitted data stream, clocked by OLRCK.
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13.5
Hardware Mode 4 Description
(Transceive Data Flow, No SRC)
Hardware mode 4 data flow is shown in Figure 27. Audio data is input via the AES3 receiver, and routed to
the serial audio output port. Different audio data synchronous to RMCK may be input into the serial audio
input port, and output via the AES3 transmitter.
The channel status data, user data, and validity bit information are handled in two alternative modes: 4A
and 4B, determined by a start-up resistor on the COPY pin. In mode 4A, the received PRO, COPY, ORIG,
EMPH, and AUDIO channel status bits are output on pins. The transmitted channel status bits are copied
from the received channel status data, and the transmitted U and V bits are 0.
In mode 4B, only the COPY and ORIG pins are output, and reflect the received channel status data. The
transmitted channel status bits, user data, and validity bits are input serially via the PRO/C, EMPH/U, and
AUDIO/V pins. Figure 20 shows the timing requirements.
The APMS pin allows the serial audio input port to be set to master or slave.
If a validity, parity, bi-phase, or lock receiver error occurs, the current audio sample is passed unmodified
to the serial audio output port.
Start-up options are shown in Table 13, and allow choice of the serial audio output port as a master or slave,
whether TCBL is an input or an output, the audio serial ports formats, and the source of the transmitted C,
U, and V data.
The following pages contain the detailed pin descriptions for Hardware mode 4.
VD+
DFC0
DFC1
VD+
H/S
OSCLK
ISCLK
SDOUT OLRCK ILRCK
SDIN
Serial
Audio
Output
RXP
RXN
AES3 Rx
&
Decoder
Serial
Audio
Input
APMS
AES3
Encoder
& Tx
TXP
TXN
C & U bit Data Buffer
RMCK
RERR
PRO/C COPY ORIG EMPH/U AUDIO/V
TCBL
Power supply pins (VD+, VA+, DGND, AGND) & the reset pin (RST) and the PLL filter pin (FILT)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 27. Hardware Mode 4 - Transceive Data Flow, Without SRC
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67
CS8420
SDOUT RMCK RERR ORIG COPY
Function
LO
Serial Output Port is Slave
HI
Serial Output Port is Master
LO Mode 4A: C transmitted data is copied from received data, U & V =0,
received PRO, EMPH, AUDIO is visible
HI Mode 4B: CUV transmitted data is input serially on pins, received PRO,
EMPH and AUDIO is not visible
LO
LO
Serial Input & Output Format IF1&OF1
LO
HI
Serial Input & Output Format IF2&OF2
HI
LO
Serial Input & Output Format IF3&OF3
HI
HI
Serial Input & Output Format IF1&OF5
LO
TCBL is an input
HI
TCBL is an output
Table 13. Hardware Mode 4 Start-Up Options
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13.5.1 Pin Description - Hardware Mode 4
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, according to Table 5.
Audio Input Interface:
SDIN - Serial Audio Input Port Data Input
Audio data serial input pin. This data will be transmitted out the AES3 port.
ISCLK - Serial Audio Input Port Bit Clock Input or Output
Serial bit clock for audio data on the SDIN pin.
ILRCK - Serial Audio Input Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDIN pin. The frequency will be at the input sample rate (Fsi)
APMS - Serial Audio Input Port Master or Slave
APMS should be connected to VD+ to set serial audio input port as a master, or connected to DGND to set the port
as a slave.
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
DS245F4
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CS8420
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the input sample rate (Fsi).
AES3/SPDIF Transmitter Interface:
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
TCBL - Transmit Channel Status Block Start
When operated as output, TCBL is high during the first sub-frame of a transmitted channel status block, and low at
all other times. When operated as input, driving TCBL high for at least three RMCK clocks will cause the current
transmitted sub-frame to be the start of a channel status block.
AES3/SPDIF Receiver Interface:
RXP, RXN - Differential Line Receiver Inputs
Differential line receiver inputs, carrying AES3 type data.
RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 256x the input sample rate (Fsi). This is also
a start-up option pin, and requires a pull-up or pull-down resistor.
RERR - Receiver Error Indicator Output
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
sub-frame of incoming AES3 data. Conditions that cause RERR to go high are: parity error, and bi-phase coding
error, as well as loss of lock in the PLL. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
EMPH/U - Pre-emphasis Indicator Output or U-Bit Data Input
The EMPH/U pin either reflects the state of the EMPH channel status bit in the incoming AES3 type data stream, or
is the serial U-bit input for the AES3 type transmitted data, clocked by OLRCK. If indicating emphasis EMPH/U is
high when the incoming data indicates 50/15 μs pre-emphasis and low otherwise.
COPY - Copy Channel Status Bit Output
The COPY pin reflects the state of the COPY Channel Status bit in the incoming AES3 type data stream. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
ORIG - Original Channel Status Output
SCMS generation indicator. This is decoded from the incoming category code and the L bit. A low output indicates
that the audio data stream is 1st generation or higher. A high indicates that the audio data stream is original. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
PRO/C - Professional Channel Status Bit Output or C-Bit Data Input
The PRO/C pin either reflects the state of the Professional/Consumer Channel Status bit in the incoming AES3 type
data stream, or is the serial C-bit input for the AES3 type transmitted data, clocked by OLRCK.
AUDIO/V - Audio Channel Status Bit Output or V-Bit Data Input
The AUDIO/V pin either reflects the state of the audio/non audio Channel Status bit in the incoming AES3 type data
stream, or is the V-bit data input for the AES3 type transmitted data stream, clocked by OLRCK.
70
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13.6
Hardware Mode 5 Description
(AES3 Receiver Only)
Hardware Mode 5 data flow is shown in Figure 28. Audio data is input via the AES3 receiver, and routed to
the serial audio output port. The PRO, COPY, ORIG, EMPH, and AUDIO channel status bits are output on
pins. The decoded C and U bits are also output, clocked by both edges of OLRCK (Master mode only, see
Figure 19).
If a validity, parity, bi-phase, or lock receiver error occurs, the current audio sample is passed unmodified
to the serial audio output port.
Start-up options are shown in Table 14, and allow choice of the serial audio output port as a master or slave,
and the serial audio port format. The following pages contain the detailed pin descriptions for Hardware
mode 5.
VD+
VD+
DFC0
DFC1
VD+
H/S
S/AES
OMCK
RXP
RXN
AES3 Rx
&
Decoder
Serial
Audio
Output
C & U bit Data Buffer
RMCK
OLRCK
OSCLK
SDOUT
C
U
RERR NVERR CHS COPY ORIG EMPH PRO AUDIO RCBL
Power supply pins (VD+, VA+, DGND, AGND) & the reset pin (RST) and the PLL filter pin (FILT)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 28. Hardware Mode 5 - AES3 Receiver Only
SDOUT
ORIG
EMPH
LO
HI
-
LO
LO
HI
HI
LO
HI
LO
HI
Function
Serial Output Port is Slave
Serial Output Port is Master
Serial Output Format OF1
Serial Output Format OF2
Serial Output Format OF3
Serial Output Format OF5
Table 14. Hardware Mode 5 Start-Up Options
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13.6.1 Pin Description - Hardware Mode 5
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, according to Table 5.
S/AES - Serial Audio or AES3 Input Select
S/AES is connected to DGND in Hardware mode 5, in order to select the AES3 input.
OMCK - Output Section Master Clock Input
Output section master clock input. This pin is not used in this mode and should be connected to DGND.
Audio Output Interface:
SDOUT - Serial Audio Output Port Data Output
Audio data serial output pin. This is also a start-up option pin, and requires a pull-up or pull-down resistor.
OSCLK - Serial Audio Output Port Bit Clock Input or Output
Serial bit clock for audio data on the SDOUT pin.
OLRCK - Serial Audio Output Port Left/Right Clock Input or Output
Word rate clock for the audio data on the SDOUT pin. The frequency will be at the input sample rate (Fsi).
72
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AES3/SPDIF Receiver Interface:
RXP, RXN - Differential Line Receiver Inputs
Differential line receiver inputs, carrying AES3 type data.
RMCK - Input Section Recovered Master Clock Output
Input section recovered master clock output. Will be at a frequency of 256x the input sample rate (Fsi).
RERR - Receiver Error Indicator
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
sub-frame of incoming AES3 data. Conditions that cause RERR to go high are: validity, parity error, and bi-phase
coding error, as well as loss of lock in the PLL.
NVERR - No Validity Receiver Error Indicator
When high, indicates a problem with the operation of the AES3 receiver. The status of this pin is updated once per
frame of incoming AES3 data. Conditions that cause NVERR to go high are: parity error, and bi-phase coding error,
as well as loss of lock in the PLL.
EMPH - Pre-emphasis Indicator Output
EMPH is low when the incoming AES3 data indicates the presence of 50/15 μs pre-emphasis. When the AES3 data
indicates the absence of pre-emphasis or the presence of non 50/15 μs pre-emphasis EMPH is high. This is also a
start-up option pin, and requires a pull-up or pull-down resistor.
COPY - Copy Channel Status Bit Output
The COPY pin reflects the state of the COPY Channel Status bit in the incoming AES3 type data stream.
ORIG - Original Channel Status Output
SCMS generation indicator. This is decoded from the incoming category code and the L bit. A low output indicates
that the audio data stream is 1st generation or higher. A high indicates that the audio data stream is original. This is
also a start-up option pin, and requires a pull-up or pull-down resistor.
PRO - Professional Channel Status Bit Output
The PRO pin reflects the state of the Professional/Consumer Channel Status bit in the incoming AES3 type data
stream.
AUDIO - Audio Channel Status Bit Output
The AUDIO pin reflects the state of the audio/non audio Channel Status bit in the incoming AES3 type data stream.
RCBL - Receiver Channel Status Block Output
RCBL indicates the beginning of a received channel status block. RCBL goes high 2 frames after the reception of a
Z preamble, remains high for 16 frames while COPY, ORIG, AUDIO, EMPH and PRO are updated, and returns low
for the remainder of the block. RCBL changes on rising edges of RMCK.
CHS - Channel Select Input
Selects which sub-frame’s channel status data is output on the EMPH, COPY, ORIG, PRO and AUDIO pins. Channel A is selected when CHS is low, channel B is selected when CHS is high.
U - User Data Output
The U pin outputs user data from the AES3 receiver, clocked by rising and falling edges of OLRCK.
C - Channel Status Data Output
The C pin outputs channel status data from the AES3 receiver, clocked by rising and falling edges of OLRCK.
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13.7
Hardware Mode 6 Description
(AES3 Transmitter Only)
Hardware Mode 6 data flow is shown in Figure 29. Audio data is input via the serial audio input port and
routed to the AES3 transmitter.
The transmitted channel status, user, and validity data may be input in two alternative methods, determined
by the state of the CEN pin. Mode 6A is selected when the CEN pin is low. In mode 6A, the user data and
validity bit are input via the U and V pins, clocked by both edges of ILRCK. The channel status data is derived from the state of the COPY/C, ORIG, EMPH, and AUDIO pins. Table 15 shows how the COPY/C and
ORIG pins map to channel status bits. In consumer mode, the transmitted category code shall be set to
Sample Rate Converter (0101100b).
Mode 6B is selected when the CEN pin is high. In mode 6B, the channel status, user data and validity bit
are input serially via the COPY/C, U, and V pins. These pins are clocked by both edges of ILRCK (if the port
is in Master mode). Figure 20 shows the timing requirements.
The channel status block pin (TCBL) may be an input or an output, determined by the state of the TCBLD
pin. The serial audio input port data format is selected as shown in Table 15, and may be set to master or
slave by the state of the APMS input pin.
The following pages contain detailed pin descriptions for Hardware mode 6.
VD+
DFC0
ILRCK
ISCLK
SDIN
VD+
DFC1
VD+
VD+
S/AES
Serial
Audio
Input
H/S
Output
Clock
Source
FILT
OMCK
AES3
Encoder
& Tx
C, U, V Data Buffer
APMS SFMT1 SFMT0
TXP
TXN
CEN
U
V
COPY/C ORIG EMPH AUDIO TCBL TCBLD
Power supply pins (VD+, VA+, DGND, AGND) & the reset pin (RST)
are omitted from this diagram. Please refer to the Typical Connection Diagram for hook-up details.
Figure 29. Hardware Mode 6 - AES3 Transmitter Only
74
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COPY/C
ORIG
0
0
1
1
0
1
0
1
Function
PRO=0, COPY=0, L=0
PRO=0, COPY=0, L=1
PRO=0, COPY=1, L=0
PRO=1
Table 15. HW 6 COPY/C and ORIG Pin Function
SFMT1
SFMT0
0
0
1
1
0
1
0
1
Function
Serial Input Format IF1
Serial Input Format IF2
Serial Input Format IF3
Serial Input Format IF4
Table 16. HW 6 Serial Port Format Selection
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CS8420
13.7.1 Pin Description - Hardware Mode 6
COPY/C
DFC0
EMPH
SFMT0
SFMT1
VA+
AGND
FILT
RST
APMS
TCBLD
ILRCK
ISCLK
SDIN
1
2
3
4
5
6*
7*
8*
9*
10
11
12
13
14
28
27
26
25
*24
*23
*22
21
20
19
18
17
16
15
ORIG
DFC1
TXP
TXN
H/S
VD+
DGND
OMCK
S/AES
AUDIO
U
V
CEN
TCBL
* Pins which remain the same function in all modes.
Overall Device Control:
DFC0, DFC1 - Data Flow Control Inputs
DFC0 and DFC1 inputs determine the major data flow options available in Hardware mode, according to Table 5.
S/AES - Serial Audio or AES3 Input Select
S/AES is connected to VD+ in Hardware mode 6, in order to select the serial audio input.
SFMT0, SFMT1 - Serial Audio Input Port Data Format Select Inputs
SFMT0 and SFMT1 select the serial audio input port format. See Table 15.
OMCK - Output Section Master Clock Input
Output section master clock input. The frequency must be 256x the output sample rate (Fso).
Audio Input Interface:
SDIN - Serial Audio Input Port
Data Input Audio data serial input pin.
ISCLK - Serial Audio Input Port Bit Clock
Input or Output Serial bit clock for audio data on the SDIN pin.
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CS8420
ILRCK - Serial Audio Input Port Left/Right Clock
Input or Output Word rate clock for the audio data on the SDIN pin.
APMS - Serial Audio Input Port Master or Slave.
APMS should be connected to VD+ to set serial audio input port as a master, or connected to DGND to set the port
as a slave.
AES3/SPDIF Transmitter Interface:
TXN, TXP - Differential Line Driver Outputs
Differential line driver outputs, transmitting AES3 type data. Drivers are pulled to low while the CS8420 is in the reset
state.
TCBL - Transmit Channel Status Block Start
When operated as output, TCBL is high during the first sub-frame of a transmitted channel status block, and low at
all other times. When operated as input, driving TCBL high for at least three OMCK clocks will cause the current
transmitted sub-frame to be the start of a channel status block.
TCBLD - Transmit Channel Status Block Direction Input
Connect TCBLD to VD+ to set TCBL as an output. Connect TCBLD to DGND to set TCBL as an input.
EMPH - Pre-Emphasis Indicator Input
In mode 6B, EMPH pin low sets the 3 EMPH channel status bits to indicate 50/15 μs pre-emphasis. If EMPH is high
the 3 EMPH channel status bits are set to 000 indicating no pre-emphasis.
COPY/C - COPY Channel Status Bit Input or C Bit Input
In mode 6B, the COPY/C pin determines the state of the COPY, PRO and L Channel Status bits in the outgoing
AES3 type data stream (See Table 15). In mode 6A, the COPY/C pin becomes the direct C bit input data pin.
ORIG - ORIG Channel Status Bit Input
In mode 6B, the ORIG pin determines the state of the COPY, PRO and L Channel Status bits in the outgoing AES3
type data stream. See Table 15.
AUDIO - Audio Channel Status Bit Input
In mode 6B, the AUDIO pin determines the state of the audio/non audio Channel Status bit in the outgoing AES3
type data stream.
V - Validity Bit Input
In modes 6A and 6B, the V pin input determines the state of the validity bit in the outgoing AES3 transmitted data.
This pin is sampled on both edges of the ILRCK.
U - User Data Bit Input
In modes 6A and 6B, the U pin input determines the state of the user data bit in the outgoing AES3 transmitted data.
This pin is sampled on both edges of the ILRCK.
CEN - C Bit Input Enable Mode Input
The CEN pin determines how the channel status data bits are input. When CEN is low, Hardware mode 6A is selected, where the COPY/C, ORIG, EMPH and AUDIO pins are used to enter selected channel status data. When
CEN is high, Hardware mode 6B is selected, where the COPY/C pin is used to enter serial channel status data.
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CS8420
14. EXTERNAL AES3/SPDIF/IEC60958 TRANSMITTER AND RECEIVER
COMPONENTS
This section details the external components required to interface the AES3 transmitter and receiver to cables and
fiber-optic components.
14.1
AES3 Transmitter External Components
The output drivers on the CS8420 are designed to drive both the professional and consumer interfaces. The
AES3 specification for professional/broadcast use calls for a 110 Ω source impedance and a balanced drive
capability. Since the transmitter output impedance is very low, a 110 Ω resistor should be placed in series
with one of the transmit pins. The specifications call for a balanced output drive of 2-7 volts peak-to-peak
into a 110 Ω load with no cable attached. Using the circuit in Figure 30, the output of the transformer is shortcircuit protected, has the proper source impedance, and provides a 5 volts peak-to-peak signal into a 110 Ω
load. Lastly, the two output pins should be attached to an XLR connector with male pins and a female shell,
and with pin 1 of the connector grounded.
CS8420
110-(RTXP+RTXN)
TXP
XLR
TXN
1
Figure 30. Professional Output Circuit
In the case of consumer use, the IEC60958 specifications call for an unbalanced drive circuit with an output
impedance of 75 Ω and a output drive level of 0.5 V peak-to-peak ±20% when measured across a 75 Ω load
using no cable. The circuit shown in Figure 31 only uses the TXP pin and provides the proper output impedance and drive level using standard 1% resistors. The connector for a consumer application would be an
RCA phono socket. This circuit is also short circuit protected.
CS8420
374-RTXP
TXP
90.9 Ω
RCA
Phono
TXN
Figure 31. Consumer Output Circuit
78
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The TXP pin may be used to drive TTL or CMOS gates as shown in Figure 32. This circuit may be used for
optical connectors for digital audio since they usually have TTL or CMOS compatible inputs. This circuit is
also useful when driving multiple digital audio outputs since RS422 line drivers have TTL compatible inputs.
CS8420
TXP
TTL or
CMOS Gate
TXN
Figure 32. TTL/CMOS Output Circuit
14.2
AES3 Receiver External Components
The CS8420 AES3 receiver is designed to accept both the professional and consumer interfaces. The digital audio specifications for professional use call for a balanced receiver, using XLR connectors, with 110 Ω
±20% impedance. The XLR connector on the receiver should have female pins with a male shell. Since the
receiver has a very high input impedance, a 110 Ω resistor should be placed across the receiver terminals
to match the line impedance, as shown in Figure 33. Although transformers are not required by the AES,
they are, however, strongly recommended.
XLR
CS8420
* See Text
RXP
110 Ω
110 Ω
Twisted
Pair
RXN
1
Figure 33. Professional Input Circuit
If some isolation is desired without the use of transformers, a 0.01 μF capacitor should be placed in series
with each input pin (RXP and RXN) as shown in Figure 34. However, if a transformer is not used, high
frequency energy could be coupled into the receiver, causing degradation in analog performance.
XLR
* See Text
0.01 μF
CS8420
RXP
110 Ω
110 Ω
Twisted
0.01 μF
RXN
Pair
1
Figure 34. Transformerless Professional Input Circuit
Figures 33 and 34 show an optional DC blocking capacitor (0.1 μF to 0.47 μF) in series with the cable input.
This improves the robustness of the receiver, preventing the saturation of the transformer, or any DC current
flow, if a DC voltage is present on the cable.
In the configuration of systems, it is important to avoid ground loops and DC current flowing down the shield
of the cable that could result when boxes with different ground potentials are connected. Generally, it is
good practice to ground the shield to the chassis of the transmitting unit, and connect the shield through a
capacitor to chassis ground at the receiver. However, in some cases it is advantageous to have the ground
of two boxes held to the same potential, and the cable shield might be depended upon to make that electrical
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CS8420
connection. Generally, it may be a good idea to provide the option of grounding or capacitively coupling the
shield to the chassis.
In the case of the consumer interface, the standards call for an unbalanced circuit having a receiver impedance of 75 Ω ±5%. The connector for the consumer interface is an RCA phono socket. The receiver circuit
for the consumer interface is shown in Figure 35.
0.01 μF
RCA Phono
CS8420
RXP
75 Ω
75 Ω
Coax
RXN
0.01 μF
Figure 35. Consumer Input Circuit
The circuit shown in Figure 36 may be used when external RS422 receivers, optical receivers or other
TTL/CMOS logic outputs drive the CS8420 receiver section.
TTL/CMOS
Gate
0.01 μF
CS8420
RXP
0.01 μF
RXN
Figure 36. TTL/CMOS Input Circuit
14.3
Isolating Transformer Requirements
The transformer should be capable of operating from 1.5 to 14 MHz, which is equivalent to an audio data
rate of 25 kHz to 108 kHz after bi-phase mark encoding. Transformers provide isolation from ground loops,
60 Hz noise, and common mode noise and interference. One of the important considerations when choosing transformers is minimizing shunt capacitance between primary and secondary windings. The higher the
shunt capacitance, the lower the isolation between primary and secondary, and the more coupling of high
frequency energy. This energy appears in the form of common mode noise on the receive side ground and
has the potential to degrade analog performance. Therefore, for best performance, shielded transformers
optimized for minimum shunt capacitance should be used. See Application Note 134 for a selection of manufacturers and their part numbers.
80
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15. CHANNEL STATUS AND USER DATA BUFFER MANAGEMENT
The CS8420 has a comprehensive channel status (C) and user (U) data buffering scheme, which allows automatic
management of channel status blocks and user data. Alternatively, sufficient control and access is provided to allow
the user to completely manage the C and U data via the control port.
15.1
AES3 Channel Status(C) Bit Management
The CS8420 contains sufficient RAM to store a full block of C data for both A and B channels (192x2 = 384
bits), and also 384 bits of U information. The user may read from or write to these RAMs via the control port.
Unlike the audio data, it is not possible to 'sample-rate' convert the C bits. This is because specific meanings
are associated with fixed-length data patterns, which should not be altered. Since the output data rate of the
CS8420 will differ from the input rate when sample-rate conversion is done, it is not feasible to directly transfer incoming C data to the output. The CS8420 manages the flow of channel status data at the block level,
meaning that entire blocks of channel status information are buffered at the input, synchronized to the output
timebase, and then transmitted. The buffering scheme involves a cascade of three block-sized buffers,
named D,E, and F as shown in Figure 37. The MSB of each byte represents the first bit in the serial C data
stream. For example, the MSB of byte 0 (which is at control port address 20h) is the consumer/professional
bit for channel status block A.
A
8-bits
From
AES3
Receiver
D
Received
Data
Buffer
B
8-bits
E
24
words
F
To
AES3
Transmitter
Transmit
Data
Buffer
Control Port
Figure 37. Channel Status Data Buffer Structure
The first buffer, D, accepts incoming C data from the AES receiver. The 2nd buffer, E, accepts entire blocks
of data from the D buffer. The E buffer is also accessible from the control port, allowing read and writing of
the C data. The 3rd buffer (F) is used as the source of C data for the AES3 transmitter. The F buffer accepts
block transfers from the E buffer.
If the input rate is slower than the output rate (so that in a given time interval, more channel status blocks
are transmitted than received), some buffered C blocks will be transmitted multiple times. If the input rate is
faster than the output rate, some will not be transmitted at all. This is illustrated in (Figure 38). In this manner,
channel status block integrity is maintained. If the transmitted sample count bits are important in the application, then they will need to be updated via the control port by the microcontroller for every outgoing block.
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15.1.1 Manually Accessing the E Buffer
The user can monitor the data being transferred by reading the E buffer, which is mapped into the register
space of the CS8420, via the control port. The user can modify the data to be transmitted by writing to the
E buffer.
Fso > Fsi (3/2) Causes blocks 1 and 3 to be transmitted twice
Contents of E buffer
Updated at Fsi rate
block 1
Contents of F buffer
Updated from E
Output at Fso rate
block 1
block 2
block 1
block 3
block 2
block 5
block 4
block 3
block 3
block 4
block 5
Fso < Fsi (2/3) Causes blocks 3 and 6 to not be transmitted
Contents of E buffer
Updated at Fsi rate
Contents of F buffer
Updated from E
Output at Fso rate
block 1
block 2
block 1
block 4
block 3
block 5
block 4
block 2
block 6
block 5
block 7
block 7
Figure 38. Channel Status Block Handling When Fso is Not Equal to Fsi
The user can configure the interrupt enable register to cause interrupts to occur whenever D-to-E or E-toF buffer transfers occur. This allows determination of the allowable time periods to interact with the E buffer.
Also provided are D-to-E and E-to-F inhibit bits. The associated buffer transfer is disabled whenever the
user sets these bits. These may be used whenever “long” control port interactions are occurring. They can
also be used to align the behavior of the buffers with the selected audio data flow. For example, if the
audio data flow is serial port in to AES3 out, then it is necessary to inhibit D-to-E transfers, since these
would overwrite the desired transmit C data with invalid data.
Flowcharts for reading and writing to the E buffer are shown in Figures 39 and 40. For reading, since a Dto-E interrupt just occurred, then there a substantial time interval until the next D-to-E transfer (approximately 192 frames worth of time). This is usually plenty of time to access the E data without having to
inhibit the next transfer. For writing, the sequence starts after a E-to-F transfer, which is based on the output timebase. Since a D-to-E transfer could occur at any time (this is based on the input timebase), then
it is important to inhibit D-to-E transfers while writing to the E buffer until all writes are complete. Then wait
until the next E-to-F transfer occurs before enabling D-to-E transfers. This ensures that the data written
to the E buffer actually gets transmitted and not overwritten by a D-to-E transfer.
If the channel status block to transmit indicates PRO mode, then the CRCC byte is automatically calculated by the CS8420, and does not have to be written into the last byte of the block by the host microcontroller.
D to E interrupt occurs
Optionally set D to E inhibit
Read E data
If set, clear D to E inhibit
Return
Figure 39. Flowchart for Reading the E Buffer
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.
E to F interrupt occurs
Optionally set E to F inhibit
Set D to E inhibit
Write E data
If set, clear E to F inhibit
Wait for E to F transfer
Clear D to E inhibit
Return
Figure 40. Flowchart for Writing the E Buffer
15.1.2 Reserving the First 5 Bytes in the E Buffer
D-to-E buffer transfers periodically overwrite the data stored in the E buffer. This can be a problem for
users who want to transmit certain channel status settings which are different from the incoming settings.
In this case, the user would have to superimpose his settings on the E buffer after every D-to-E overwrite.
To avoid this problem, the CS8420 has the capability of reserving the first 5 bytes of the E buffer for user
writes only. When this capability is in use, internal D-to-E buffer transfers will NOT affect the first 5 bytes
of the E buffer. Therefore, the user can set values in these first 5 E bytes once, and the settings will persist
until the next user change. This mode is enabled via the Channel Status Data Buffer Control register.
15.1.3 Serial Copy Management System (SCMS)
In Software mode, the CS8420 allows read/modify/write access to all the channel status bits. For Consumer mode SCMS compliance, the host microcontroller needs to read and manipulate the Category
Code, Copy bit and L bit appropriately.
In Hardware mode, the SCMS protocol can be followed by either using the COPY and ORIG input pins,
or by using the C bit serial input pin. These options are documented in the Hardware mode section of this
data sheet (See “Hardware Modes” on page 55)
15.1.4 Channel Status Data E Buffer Access
The E buffer is organized as 24 x 16-bit words. For each word the MS Byte is the A channel data, and the
LS Byte is the B channel data (see Figure 37).
There are two methods of accessing this memory, known as one-byte mode and two-byte mode. The desired mode is selected via a control register bit.
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15.1.5 One-Byte Mode
In many applications, the channel status blocks for the A and B channels will be identical. In this situation,
if the user reads a byte from one of the channel's blocks, the corresponding byte for the other channel will
be the same. Similarly, if the user wrote a byte to one channel's block, it would be necessary to write the
same byte to the other block. One-Byte mode takes advantage of the often identical nature of A and B
channel status data.
When reading data in one-byte mode, a single byte is returned, which can be from channel A or B data,
depending on a register control bit. If a write is being done, the CS8420 expects a single byte to be input
to its control port. This byte will be written to both the A and B locations in the addressed word.
One-Byte mode saves the user substantial control port access time, as it effectively accesses 2 bytes’
worth of information in 1 byte's worth of access time. If the control port's auto-increment addressing is
used in combination with this mode, multi-byte accesses such as full-block reads or writes can be done
especially efficiently.
15.1.6 Two-Byte Mode
There are those applications in which the A and B channel status blocks will not be the same, and the
user is interested in accessing both blocks. In these situations, Two-Byte mode should be used to access
the E buffer.
In this mode, a read will cause the CS8420 to output two bytes from its control port. The first byte out will
represent the A channel status data, and the 2nd byte will represent the B channel status data. Writing is
similar, in that two bytes must now be input to the CS8420's control port. The A channel status data is
first, B channel status data second.
15.2
AES3 User (U) Bit Management
The CS8420 U bit manager has four operating modes:
Mode 1. Transmit all zeros
Mode 2. Block mode
Mode 3. Reserved
Mode 4. IEC Consumer B
15.2.1 Mode 1: Transmit All Zeros
Mode 1 causes only zeros to be transmitted in the output U data, regardless of E buffer contents or U data
embedded in an input AES3 data stream. This mode is intended for the user who does not want to transceive U data, and simply wants the output U channel to contain no data.
15.2.2 Mode 2: Block Mode
Mode 2 is very similar to the scheme used to control the C bits. Entire blocks of U data are buffered from
input to output, using a cascade of three block-sized RAMs to perform the buffering. The user has access
to the second of these three buffers, denoted the E buffer, via the control port. Block mode is designed
for use in AES3 in, AES3 out situations in which input U data is decoded using a microcontroller via the
control port. It is also the only mode in which the user can merge his/her own U data into the transmitted
AES3 data stream.
The U buffer access only operates in Two-Byte mode, since there is no concept of A and B blocks for user
data. The arrangement of the data in the each byte is that the MSB is the first received bit and is the first
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transmitted bit. The first byte read is the first byte received, and the first byte sent is the first byte transmitted.
15.2.3 IEC60958 Recommended U Data Format for Consumer Applications
Modes (3) and (4) are intended for use in AES3 in, AES3 out situations, in which the input U data is formatted as recommended in the “IEC60958 Digital Audio Interface, part 3: Consumer applications” document.
In this format, “messages” are formed in the U data from Information Units or IUs. An IU is 8 bits long, and
the MSB is always 1, and is called the start bit, or 'P' bit. The remaining 7-bits are called Q, R, S, T, U, V,
& W, and carry the desired data.
A “message” consists of 3 to 129 IUs. Multiple IUs are considered to be in the same message if they are
separated by 0 to 8 zeros, denoted here as filler. A filler sequence of nine or more zeros indicates an intermessage gap. The desired information is normally carried in the sequence of corresponding bits in the
IUs. For example, the sequential Q bits from each IU make up the Q sub-code data that is used to indicate
Compact Disk track information. This data is automatically extracted from the received IEC60958 stream,
and is presented in the control port register map space.
Where incoming U data is coded in the above format, and needs to be re-transmitted, the data transfer
cannot be done using shift registers, because of the different Fsi and Fso sampling clocks. Instead, input
data must be buffered in a FIFO structure, and then read out by the AES3 transmitter at appropriate times.
Each bit of each IU must be transceived; unlike the audio samples, there can be no sample rate conversion of the U data. Therefore, there are two potential problems:
(1) Message Partitioning
When Fso > Fsi, more data is transmitted than received per unit time. The FIFO will frequently be completely emptied. Sensible behavior must occur when the FIFO is empty, otherwise, a single incoming message may be erroneously partitioned into multiple, smaller, messages.
(2) Overwriting
When Fso < Fsi, more data is received than transmitted per unit time. There is a danger of the FIFO becoming completely full, allowing incoming data to overwrite data that has not yet been output through the
AES3 transmitter.
15.2.4 Mode (3): Reserved
This mode has been removed. Use IEC Consumer mode B.
15.2.5 Mode (4): IEC Consumer B
In this mode, the partitioning problem is solved by buffering an entire message before starting to transmit
it. In this scheme, zero-segments between messages will be expanded when Fso > Fsi, but the integrity
of individual messages is preserved.
The overwriting problem (when Fso < Fsi) is solved by only storing a portion of the input U data in the
FIFO. Specifically, only the IUs themselves are stored (and not the zeros that provide inter-IU and intermessage “filler”). An inter-IU filler segment of fixed length (OF) will be added back to the messages at the
FIFO output, where the length of OF is equal to the shortest observed input filler segment (IF).
Storing only IUs (and not filler) within the FIFO makes it possible for the slower AES3 transmitter to “catch
up” to the faster AES3 receiver as data is read out of the FIFO. This is because nothing is written into the
FIFO when long strings of zeros are input to the AES-EBU receiver. During this time of no writing, the
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transmitter can read out data that had previously accumulated, allowing the FIFO to empty out. If the FIFO
becomes completely empty, zeros are transmitted until a complete message is written into the FIFO.
Mode 4 is not fail-safe; the FIFO can still get completely full if there isn't enough “zero-padding” between
incoming messages. It is up to the user to provide proper padding, as defined below:
Minimum padding
= (Fsi/Fso - 1)*[8N + (N-1)*IF +9] + 9
where N is the number of IUs in the message, IF is the number of filler bits between each IU, and Fso ≤ Fsi.
Example 1: Fsi/Fso = 2, N=4, IF=1: minimum proper padding is 53 bits.
Example 2: Fsi/Fso = 1, N=4, IF=7: min proper padding is 9 bits.
The CS8420 detects when an overwrite has occurred in the FIFO, and synchronously resets the entire
FIFO structure to prevent corrupted U data from being merged into the transmitted AES3 data stream.
The CS8420 can be configured to generate an interrupt when this occurs.
Mode 4 is recommended for properly formatted U data where mode 3 cannot provide acceptable performance, either because of a too-extreme Fsi/Fso ratio, or because it's unacceptable to change the lengths
of filler segments. Mode 4 provides error-free performance over the complete range of Fsi/Fso ratios (provided that the input messages are properly zero-padded for Fsi > Fso).
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16. PLL FILTER
16.1
General
An on-chip Phase Locked Loop (PLL) is used to recover the clock from the incoming data stream. Figure
41 is a simplified diagram of the PLL in CS8420 devices. When the PLL is locked to an AES3 input stream,
it is updated at each preamble in the AES3 stream. This occurs at twice the sampling frequency, FS. When
the PLL is locked to ILRCK, it is updated at FS so that the duty cycle of the input doesn’t affect jitter.
There are some applications where low jitter in the recovered clock, presented on the RMCK pin, is important. For this reason, the PLL has been designed to have good jitter attenuation characteristics, as shown
in Figure 44 and Figure 45. In addition, the PLL has been designed to use only the preambles of the AES3
stream to provide lock update information to the PLL. This results in the PLL being immune to data-dependent jitter effects because the AES3 preambles do not vary with the data.
The PLL has the ability to lock onto a wide range of input sample rates with no external component changes.
If the sample rate of the input subsequently changes, for example in a varispeed application, the PLL will
only track up to ±12.5% from the nominal center sample rate. The nominal center sample rate is the sample
rate that the PLL first locks onto upon application of an AES3 data stream or after enabling the CS8420
clocks by setting the RUN control bit. If the 12.5% sample rate limit is exceeded, the PLL will return to its
wide lock range mode and re-acquire a new nominal center sample rate.
INPUT
Phase
Comparator
and Charge Pump
VCO
RMCK
Rfilt
Cfilt
Crip
÷N
Figure 41. PLL Block Diagram
16.2
External Filter Components
16.2.1 General
The PLL behavior is affected by the external filter component values. Figure 5 on page 12 shows the recommended configuration of the two capacitors and one resistor that comprise the PLL filter. In Table 19
and Table 20, the component values shown for the 32 to 96 kHz range have the highest corner frequency
jitter attenuation curve, takes the shortest time to lock, and offers the best output jitter performance. The
component values shown in Table 18 and Table 20 for the 8 to 96 kHz range allows the lowest input sample rate to be 8 kHz, and increases the lock time of the PLL. Lock times are worst case for an Fsi transition
of 96 kHz.
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16.2.2 Capacitor Selection
The type of capacitors used for the PLL filter can have a significant effect on receiver performance. Large
or exotic film capacitors are not necessary as their leads and the required longer circuit board traces add
undesirable inductance to the circuit. Surface mount ceramic capacitors are a good choice because their
own inductance is low, and they can be mounted close to the FILT pin to minimize trace inductance. For
CRIP, a C0G or NPO dielectric is recommended, and for CFILT, an X7R dielectric is preferred. Avoid capacitors with large temperature coefficients, or capacitors with high dielectric constants, that are sensitive
to shock and vibration. These include the Z5U and Y5V dielectrics.
16.2.3 Circuit Board Layout
Crip
Rfilt
1000
pF
FILT
VA+
AGND
Board layout and capacitor choice affect each other and determine the performance of the PLL. Figure
42 contains a suggested layout for the PLL filter components and for bypassing the analog supply voltage.
The 0.1 µF bypass capacitor is in a 1206 form factor. RFILT and the other three capacitors are in an 0805
form factor. The traces are on the top surface of the board with the IC so that there is no via inductance.
The traces themselves are short to minimize the inductance in the filter path. The VA+ and AGND traces
extend back to their origin and are shown only in truncated form in the drawing.
.1µF
Cfilt
Figure 42. Recommended Layout Example
16.3
Component Value Selection
When transitioning from one revision of the part another, component values need to be changed. It is mandatory for customers to change the external PLL component values when transitioning from revision D to
revision D1.
16.3.1 Identifying the Part Revision
The first line of the part marking on the package indicates the part number and package type
CS8420-xx. Table 17 shows a list of part revisions and their corresponding second line part marking,
which indicates what revision the part is.
Revision
D
D1
Pre-October 2002 (10-Digit)
Zxxxxxxxxx
Rxxxxxxxxx
New (12-Digit)
ZFBADXxxxxxx
RFBAD1xxxxxx
Table 17. Second Line Part Marking
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16.3.2 Locking to the RXP/RXN Receiver Inputs
CS8420 parts that are configured to lock to only the RXP/RXN receiver inputs should use the external
PLL component values listed in Table 18 and Table 19. Values listed for the 32 to 96 kHz Fs range will
have the highest corner frequency jitter attenuation curve, take the shortest time to lock, and offer the best
output jitter performance.
Revision
RFILT (kΩ)
CFILT (μF)
CRIP (nF)
PLL Lock Time (ms)
D
0.909
1.8
33
56
D1
0.4
0.47
47
60
Table 18. Locking to RXP/RXN - Fs = 8 to 96 kHz
Revision
RFILT (kΩ)
CFILT (μF)
CRIP (nF)
PLL Lock Time (ms)
D
3.0
0.047
2.2
35
D1
1.6
0.33
4.7
35
Table 19. Locking to RXP/RXN - Fs = 32 to 96 kHz*
* Parts used in applications that are required to pass the AES3 or IEC60958-4 specification for receiver
jitter tolerance should use these component values. Please note that the AES3 and IEC60958 specifications do not have allowances for locking to sample rates less than 32 kHz or for locking to the ILRCK input.
Also note that many factors can affect jitter performance in a system. Please follow the circuit and layout
recommendations outlined previously.
16.3.3 Locking to the ILRCK Input
CS8420 parts that are configured to lock to the ILRCK input should use the external PLL component values listed in Table 20. Note that parts that need to lock to both ILRCK and RXP/RXN should use
these values. Values listed for the 32 to 96 kHz Fs range will have the highest corner frequency jitter attenuation curve, take the shortest time to lock, and offer the best output jitter performance.
Revision
D
Fs Range
RFILT (kΩ) CFILT (μF) CRIP (nF) PLL Lock Time (ms)
(kHz)
8 to 96
1.3
2.7
62
120
D
32-96
5.1
0.15
3.9
70
D1
8 to 96
0.3
1.0
100
120
D1
32-96
0.6
0.22
22
70
Table 20. Locking to the ILRCK Input
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16.3.4 Jitter Tolerance
Shown in Figure 43 is the Receiver Jitter Tolerance template as illustrated in the AES3 and IEC60958-4
specification. CS8420 parts used with the appropriate external PLL component values (as noted in
Table 19) have been tested to pass this template.
Figure 43. Jitter Tolerance Template
16.3.5 Jitter Attenuation
Shown in Figure 44 and Figure 45 are jitter attenuation plots for the various revisions of the CS8420 when
used with the appropriate external PLL component values (as noted in Table 19). The AES3 and
IEC60958-4 specifications do not have allowances for locking to sample rates less than 32 kHz or for locking to the ILRCK input. These specifications state a maximum of 2 dB jitter gain or peaking.
5
5
0
0
Jitter Attenuation (dB)
Jitter Attenuation (dB)
−5
−5
−10
−10
−15
−15
−20
−20
−1
10
0
10
1
10
2
10
Jitter Frequency (Hz)
3
10
4
10
Figure 44. Revision D Jitter Attenuation
90
5
10
−25
−1
10
0
10
1
10
2
10
Jitter Frequency (Hz)
3
10
4
10
5
10
Figure 45. Revision D1 Jitter Attenuation
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17. PARAMETER DEFINITIONS
Input Sample Rate (Fsi)
The sample rate of the incoming digital audio.
Input Frame Rate
The frame rate of the received AES3 format data.
Output Sample Rate (Fso)
The sample rate of the outgoing digital audio.
Output Frame Rate
The frame rate of the transmitted AES3 format data.
Dynamic Range
The ratio of the maximum signal level to the noise floor.
Total Harmonic Distortion and Noise
The ratio of the noise and distortion to the test signal level. Normally referenced to 0 dBFS.
Peak Idle Channel Noise Component
With an all-zero input, what is the amplitude of the largest frequency component visible with a 16K point
FFT. The value is in dB ratio to full-scale.
Input Jitter Tolerance
The amplitude of jitter on the AES3 stream, or in the ILRCK clock, that will cause measurable artifacts in the
SRC output. Test signal is full scale 9 kHz, Fsi is 48 kHz, Fso is different 48 kHz, jitter is 2 kHz sinusoidal,
and audio band white noise.
AES3 Transmitter Output Jitter
With a jitter free OMCK clock, what is the jitter added by the AES3 transmitter.
Gain Error
The difference in amplitude between the output and the input signal level, within the passband of the digital
filter in the SRC.
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18. PACKAGE DIMENSIONS
28L SOIC (300 MIL BODY) PACKAGE DRAWING
E
H
1
b
c
∝
D
L
SEATING
PLANE
A
e
A1
INCHES
DIM
MIN
MAX
A
A1
B
C
D
E
e
H
L
0.093
0.004
0.013
0.009
0.697
0.291
0.040
0.394
0.016
0°
0.104
0.012
0.020
0.013
0.713
0.299
0.060
0.419
0.050
8°
∝
MILLIMETERS
MIN
MAX
2.35
0.10
0.33
0.23
17.70
7.40
1.02
10.00
0.40
0°
2.65
0.30
0.51
0.32
18.10
7.60
1.52
10.65
1.27
8°
THERMAL CHARACTERISTICS AND SPECIFICATIONS
Parameter
Junction to Ambient thermal impedance (28 pin SOIC)
Allowable Junction Temperature
92
Symbol
Min
Typ
Max
Units
θJA
-
TJ
-
65
-
°C/W
-
135
°C
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19. ORDERING INFORMATION
Product
Description
Package Pb-Free
No
CS8420
Digital Audio Sample
28-SOIC
Rate Converter
Grade
Temp Range
Commercial -10º to +70ºC
Commercial -10º to +70ºC
Yes
Automotive -40º to +85ºC
CDB8420
Evaluation Board for
CS8420
-
-
-
Container
Order#
Rail
CS8420-CS
Tape and Reel CS8420-CSR
Rail
CS8420-CSZ
Tape and Reel CS8420-CSZR
Rail
CS8420-DSZ
Tape and Reel CS8420-DSZR
-
-
CDB8420
20. REVISION HISTORY
Release
Changes
PP1
1st Preliminary Release
PP2
2nd Preliminary Release
PP3
3rd Preliminary Release
PP4
-Added IS package to front page.
-Added IS package to “Ambient Operating Temperature:” on page 6.
-Corrected “Minimizing Group Delay Through Multiple CS8420s When Locking to ILRCK” on page 28.
-Revised “SRC Invalid State” on page 49.
PP5
-Added DS package to front page.
-Added DS package to “Ambient Operating Temperature:” on page 6.
-Corrected “tdpd” on page 9.
-Corrected “tlmd” on page 9.
-Corrected “tsmd” on page 9.
-Corrected “tdh” on page 10.
-Added “C/U Buffer Data Corruption” on page 49
PP6
-Added lead-free ordering information.
F1
Final Release 1
-Changed format of Figure 17 on page 20 and Figure 18 on page 21.
-Changed SORES description to refer to sample rate converter as data source in “Serial Audio Output Port
Data Format (06h)” on page 39.
-Added “Transmitter Startup” on page 48.
-Integrated D1 Errata in Section 16.2 on page 87 .
F2
Final Release 2
-Updated Ordering Information.
-Added “Block-Mode U-Data D-to-E Buffer Transfers” on page 50.
F3
Final Release 3
-Updated Ordering Information.
F4
Final Release 4
-Updated Leaded/Lead-Free information in “Ordering Information” on page 93.
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Contacting Cirrus Logic Support
For all product questions and inquiries, contact a Cirrus Logic Sales Representative.
To find the one nearest you, go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus
for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third
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does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
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IN AIRCRAFT SYSTEMS, MILITARY APPLICATIONS, PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED,
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THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL
APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND
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Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks
or service marks of their respective owners.
SPI is a trademark of Motorola Inc.
AC-3 is a registered trademark of Dolby Laboratories, Inc.
I²C is a registered trademark of Philips Semiconductor.
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