CONEXANT BT8954

Bt8954
Voice Pair Gain Framer
The Bt8954 framer has been tailored specifically to meet the needs of voice pair gain
systems (also referred to as “cable relief systems” and “digital subscriber line carriers”)
by providing a direct connection to the DSL modem and the CODEC. It performs data,
clock, and format conversions necessary to construct a Pulse Code Multiplexed (PCM)
channel from a Symmetrical Digital Subscriber Line (SDSL) or a High-Bit-Rate Digital
Subscriber Line (HDSL) channel. The PCM channel consists of transmit and receive
data, clock, and frame sync signals configured for 2–18 voice channels. The PCM
channel connects directly to popular PCM codecs. The Digital Subscriber Line (DSL)
channel interface consists of serial data and clock connected to a RS8973, Bt8970 or a
Bt8960 DSL Transceiver. The Bt8954 supports clear and compressed voice system.
When coupled with a Bt8960, the Bt8954 provides PCM4 functions at greater than 5 km
reach with no voice compression, allowing V.34 modem operation.
At one end, Bt8954 multiplexes payload data from several PCM codecs with the
appropriate overhead and signaling bits into one transport frame that is passed on to the
bit-pump, for transport over a single twisted pair. At the other end, Bt8954
demultiplexes the DSL bit stream into payload data sent to the PCM codec, and
overhead data written into microcomputer-accessible registers.
Embedded Operations Channel (EOC) and signaling overhead can be inserted via the
Microcomputer Interface (MCI). Control and status registers are accessed via the MCI.
One common register group configures the PCM interface formatter, Phase-Locked
Loop (PLL), and PCM Loopback (LB). Another group of DSL channel registers
configures the elastic store FIFOs, overhead muxes, receive framer, payload mapper, and
the DSL loopback. Status registers monitor received overhead, PLL, FIFO, and framer
operations, including CRC and FEBE error counts.
Functional Block Diagram
2B1Q
Decoder
Payload
Demux
PCM
RFIFO
PCMR
HCLK
BCLK
LB
OH/Signaling
PLL
LB
Registers
QCLK
TDAT
2B1Q
Encoder
Payload
Mux
PCM
TFIFO
Microcomputer Interface
PCM Formatter
DSL Bit Pump
RDAT
ADPCMCK
PCMCLK
PCMF[18:1]
PCMT
ADPCM/PCM Codecs
Receive
Framer
Distinguishing Features
•
•
•
•
•
•
•
•
•
•
•
Voice Pair Gain Framer
– Frames and transports PCM data
streams over 12–18,000 ft.
(3.7–5.5 km) distances when
coupled with Bt8960 or Bt8970
PCM Interface
– Supports popular PCM codecs
– Programmable payload to
support 2–18 64 kbps voice
channels
– 2.048, 1.536 MHz PCM reference
clock generation
– 6.144, 8.192, 20.48 MHz ADPCM
reference clock generation
DSL Interface
– Connects to Bt8960 or Bt8970
– Supports 160–1168 kbps bit rates
– Error performance monitoring
– Auto tip/ring reversal
Microcomputer Interface
– Glueless interface to Intel 8051
and Motorola 68302 processors
– Access to overhead and signaling
registers
Supports ADPCM codecs (32 kbps)
PCM and DSL loopbacks
CMOS technology, 5 V operation
Low-power operation
– Enables compatibility with
line-powered systems
68-pin PLCC
JTAG/IEEE Std 1149.1-1990
–40 °C to +85 °C operation
Applications
•
•
Voice Pair Gain Systems (Clear)
– PCM2, PCM4(PCM1+3), PCM6,
– PCM8, PCM10/11, PCM12,
PCM18
ADPCM Voice Pair Gain Systems
(Compressed)
– ADPCM12, ADPCM24, ADPCM36
Microcomputer
Data Sheet
N8954DSC
April 7, 1999
Ordering Information
Model Number
Package
Ambient Temperature
Bt8954
68-Pin Plastic Leaded Chip Carrier (PLCC)
–40 °C to +85 °C
Information provided by Conexant Systems, Inc. (Conexant) is believed to be accurate and reliable. However, no responsibility is
assumed by Conexant for its use, nor any infringement of patents or other rights of third parties which may result from its use. No
license is granted by implication or otherwise under any patent rights of Conexant other than for circuitry embodied in Conexant
products. Conexant reserves the right to change circuitry at any time without notice. This document is subject to change without
notice.
Conexant and “What’s Next in Communications Technologies” are trademarks of Conexant Systems, Inc.
Product names or services listed in this publication are for identification purposes only, and may be trademarks or registered
trademarks of their respective companies. All other marks mentioned herein are the property of their respective holders.
© 1999 Conexant Systems, Inc.
Printed in U.S.A.
All Rights Reserved
Reader Response: To improve the quality of our publications, we welcome your feedback. Please send comments or
suggestions via e-mail to Conexant Reader [email protected] Sorry, we can't answer your technical
questions at this address. Please contact your local Conexant sales office or local field applications engineer if you
have technical questions.
N8954DSC
Conexant
Table of Contents
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
List of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
1.0
DSL Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1
Voice Pair Gain Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1.1
Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.1.2
Subscriber Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.2
System Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
2.0
Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
3.0
Circuit Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2
DSL Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.2.1
3.2.2
3.2.3
3.3
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.4
2B1Q Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Receive Framer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
CRC Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
Descrambler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
Payload Demux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
N8954DSC
Detailed Frame Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Differences Between the DSL and HDSL T1/E1 Frame Formats . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.2.1
EXTRA_Z_BIT Option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Overhead Bit Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
OH/Signaling Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Transmit Signaling FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
Payload Mux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
CRC Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Scrambler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
2B1Q Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Conexant
iii
Bt8954
Table of Contents
Voice Pair Gain Framer
4.0
3.5
PCM Formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
3.6
Loopbacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
3.7
Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
3.7.1
COTF Transmitter Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
3.7.2
RTF Receiver Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
3.7.3
RTF Transmitter Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
3.7.4
COTF Receiver Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
3.7.5
Round Trip Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
3.8
Microcomputer Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
3.8.1
Microcomputer Read/Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
3.8.1.1
Multiplexed Address/Data Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
3.8.1.2
Separated Address/Data Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
3.8.2
Interrupt Request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-22
3.8.3
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23
3.9
PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1
Register Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.2
Register Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.3
Address Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.4
Transmitter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
0x80, 0x81—Transmit Embedded Operations Channel (TEOC_LO, TEOC_HI) . . . . . . . . . . 4-4
0x82, 0x83—Transmit Indicator Bits (TIND_LO, TIND_HI) . . . . . . . . . . . . . . . . . . . . . . . . 4-4
0x84—Transmit Signaling FIFOs (TSFIFO_I, TSFIFO_O). . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
0x85—Transmit FIFO Water Level (TFIFO_WL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
0x86—Transmit Command Register 1 (TCMD_1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
0x87—Transmit Command Register 2 (TCMD_2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4.5
Receiver Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
0x90—Receive Command Register 1 (RCMD_1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
0x91—Receive Command Register 2 (RCMD_2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
4.6
DSL Channel Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
0xA0—DSL Frame Length (DFRAME_LEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
0xA1—Sync Word (SYNC_WORD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
0xA2, 0xA3—Rx FIFO Water Level (RFIFO_WL_LO, RFIFO_WL_HI) . . . . . . . . . . . . . . . . 4-13
4.7
PLL Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
0xB0—PLL_INT Register (PLL_INT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
0xB1—PLL_FRAC_HI Register (PLL_FRAC_HI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
0xB2—PLL_FRAC_LO Register (PLL_FRAC_LO). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
0xB3—PLL_A Register (PLL_A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
0xB4—PLL_B Register (PLL_B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
0xB5—PLL_SCALE Register (PLL_SCALE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
iv
Conexant
N8954DSC
Bt8954
Table of Contents
Voice Pair Gain Framer
4.8
Common . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
0xC0—Command Register 1 (CMD_1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
0xC1—Revision Identification (REV_ID) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
4.9
Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
0xD0—Interrupt Status Register (ISR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
0xD1—Interrupt Mask Register (IMR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
4.10 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
0xD3—Scrambler Reset (SCR_RST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
0xD4—Transmit FIFO Reset (TFIFO_RST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
0xD5—Reset Pointer to Transmit Signaling FIFOs (TSFIFO_PTR_RST). . . . . . . . . . . . . . 4-20
0xD6—Reset Pointer to Receive Signaling FIFOs (RSFIFO_PTR_RST) . . . . . . . . . . . . . . 4-20
0xD7—Receive Elastic Store FIFO Reset (RFIFO_RST) . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
0xD8—Receive Framer Synchronization Reset (SYNC_RST) . . . . . . . . . . . . . . . . . . . . . 4-21
0xD9—Error Count Reset (ERR_RST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
0xDA—Reset Receiver (RX_RST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
0xDB—Update TSFIFO_O (UPDATE_TSFIFO_O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
0xDC—Update RSFIFO_O (UPDATE_RSFIFO_O) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
4.11 Receive/Transmit Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
0xE0, 0xE1—Receive Embedded Operations Channel (REOC_LO, REOC_HI) . . . . . . . . . 4-22
0xE2, 0xE3—Receive Indicator Bits (RIND_LO, RIND_HI) . . . . . . . . . . . . . . . . . . . . . . . 4-22
0xE4—Receive Signaling FIFOs (RSFIFOs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
0xE5—Receive Status 1 (RSTATUS_1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
0xE6—Receive Status 2 (RSTATUS_2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26
0xE7—Transmit Status 1 (TSTATUS_1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27
0xE8—CRC Error Count (CRC_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
0xE9—Far End Block Error Count (FEBE_CNT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
4.12 PCM Formatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
0xF0—PCM Frame Length (PFRAME_LEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29
0xF1—PCM Format (PCM_FORMAT1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29
5.0
Electrical and Mechanical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1.1
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1.2
Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.1.3
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.1.4
DSL Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.1.5
PCM Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.1.6
Microcomputer Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
5.1.7
Test and Diagnostic Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
5.2
Mechanical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
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Conexant
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Bt8954
Table of Contents
Voice Pair Gain Framer
Appendix A: Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
vi
A.1
Interfacing to the Bt8960/Bt8970 HDSL Transceiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
A.2
Interfacing to the Texas Instrument TP3054A PCM Codec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2
A.3
Interfacing to the Motorola 68302 16-Bit Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3
A.4
Interfacing to the Intel 8051 8-Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4
A.5
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4
Conexant
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Bt8954
List of Figures
Voice Pair Gain Framer
List of Figures
Figure 1-1.
Figure 1-2.
Figure 1-3.
Figure 1-4.
Figure 2-1.
Figure 2-2.
Figure 3-1.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 3-6.
Figure 3-7.
Figure 3-8.
Figure 3-9.
Figure 3-10.
Figure 3-11.
Figure 3-12.
Figure 3-13.
Figure 3-14.
Figure 3-15.
Figure 3-16.
Figure 3-17.
Figure 3-18.
Figure 3-19.
Figure 3-20.
Figure 3-21.
Figure 3-22.
Figure 3-23.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
N8954DSC
Block Diagram of a PCM4 Voice Pair Gain Modem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
Repeater Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
Subscriber Modem (Terminal) System Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
Bt8954 System Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
Pin Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Bt8954 Functional Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
Basic DSL Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Receiver Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Receive Framer Finite State Machine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Threshold Correlation Effect on Expected SYNC Locations . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
LFSR Structure for Transmission in the Remote → Central Office Direction. . . . . . . . . . . . 3-8
LFSR Structure for Transmission in the Central Office → Remote Direction. . . . . . . . . . . . 3-8
Transmitter Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Double Buffering, Using Transmit S-Bits Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
LFSR Structure for Transmission in the Remote → Central Office Direction. . . . . . . . . . . 3-12
LFSR Structure for Transmission in the Central Office → Remote Direction. . . . . . . . . . . 3-13
PCM Formatter Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
PCMF [18:1] Waveforms for Encoded and Decoded Frame SYNC Modes. . . . . . . . . . . . . 3-15
PCM and DSL Loopbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
COTF and RTF Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
COTF Transmitter Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
RTF Receiver Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
RTF Transmitter Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18
COTF Receiver Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-19
MCI Port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-20
Functional Diagram of the Read and Write Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21
Interrupt Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-22
Functional Diagram of the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24
Transmit Signaling FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Example of Three Signaling Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
Receive Signaling FIFOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
Example of Three Signaling Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Conexant
vii
Bt8954
List of Figures
Voice Pair Gain Framer
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 5-7.
Figure 5-8.
Figure 5-9.
Figure 5-10.
Figure 5-11.
Figure 5-12.
Figure 5-13.
Figure A-1.
Figure A-2.
Figure A-3.
Figure A-4.
viii
QCLK Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
DSL Interface Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
PCM Interface Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
MCI Write Timing, Intel Mode (MOTEL = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
MCI Write Timing, Motorola Mode (MOTEL = 1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
MCI Read Timing, Intel Mode (MOTEL = 0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
MCI Read Timing, Motorola Mode (MOTEL = 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
Internal Write Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
JTAG Interface Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Input Waveforms for Timing Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
Output Waveforms for Timing Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
Output Waveforms for Three-State Enable and Disable Tests . . . . . . . . . . . . . . . . . . . . . . 5-10
68-Pin PLCC Package Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
Bt8954 to Bt8960/Bt8970 DSL Transceiver Interconnection . . . . . . . . . . . . . . . . . . . . . . . . A-1
Bt8954 to Texas Instrument TP3054A PCM Codec Interconnection . . . . . . . . . . . . . . . . . . A-2
Bt8954 to Motorola 68302 Processor Interconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3
Bt8954 to Intel 8051 Controller Interconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4
Conexant
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Bt8954
List of Tables
Voice Pair Gain Framer
List of Tables
Table 2-1.
Hardware Signal Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Table 3-1.
DSL Frame Structure and Overhead Bit Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Table 3-2.
2B1Q Decoder Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
Table 3-3.
2B1Q Encoder Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
Table 3-4.
PCM and DSL Loopbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16
Table 3-5.
PLL_X Register Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25
Table 3-6.
PLL_C Register Bit Representation of PLL_W and PLL_Y . . . . . . . . . . . . . . . . . . . . . . . . 3-26
Table 3-7.
PLL_P Register Bit Representation of P_FACTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-26
Table 3-8.
Factors for fPLL = 196.608 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-27
Table 3-9.
Factors for fPLL = 204.800 MHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-28
Table 4-1.
Address Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Table 4-2.
Transmitter Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Table 4-3.
DSL Receive Write Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Table 4-4.
DSL Channel Configuration Write Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
Table 4-5.
PLL Configuration Write Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
Table 4-6.
Common Command Write Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Table 4-7.
Interrupt Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Table 4-8.
Reset Write Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
Table 4-9.
Receive and Transmit Status Read Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
Table 4-10.
PCM Formatter Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28
Table 5-1.
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Table 5-2.
Recommended Operating Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
Table 5-3.
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Table 5-4.
QCLK Timing Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Table 5-5.
DSL Interface Switching Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
Table 5-6.
PCM Interface Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Table 5-7.
Microcomputer Interface Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
Table 5-8.
Microcomputer Interface Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Table 5-9.
Test and Diagnostic Interface Timing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
Table 5-10.
Test and Diagnostic Interface Switching Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
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Bt8954
List of Tables
Voice Pair Gain Framer
x
Conexant
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1
1.0 DSL Systems
1.1 Voice Pair Gain Applications
A well-established market exists for voice pair gain systems. In such systems,
several simultaneous phone conversations are transported over a single twisted
pair. These systems are used by telecommunications service providers to
maximize the utilization of the existing copper plant and allow it to provision
many more telephone circuits than is possible with ordinary 4 kHz analog
transport. The external interfaces of voice pair gain systems, at both the Central
Office and remote ends, are analog POTS lines. Two carrier techniques facilitate
single pair gain transmission: Frequency Domain Multiplexed Systems (FDM)
and Time Domain Multiplexed Systems (TDM). In FDM systems each voice
channel is modulated by a successively higher carrier such that the composite
transmission consists of several frequency bands. In TDM systems the voice data
is digitized and sampled in a channel-multiplexed fashion. Although FDM
systems are currently fielded, recent trends are clearly toward TDM systems
because of the inherent advantages associated with digital transmission.
Traditional PCM4 (also called “1+3”) voice pair gain systems use a
combination of 2:1 Adaptive Differential Pulse Code Modulation (ADPCM)
compression and basic rate Integrated Service Digital Network (ISDN)
U-interface devices to transport four-voice conversations on one twisted pair. The
disadvantage of this scheme is that clear 64 kbps channel capacity is lost due to
the ADPCM voice compression algorithm. This may prevent high-speed
facsimile and data transmissions from being transported reliably. Since
telecommunication service providers want to provision telephone equipment that
can be used for business purposes, this disadvantage has caused them to seek
alternative solutions that can handle data as well as voice. When used with a
Digital Subscriber Line (DSL) bit pump, such as the Bt8960, PCM4 systems can
be constructed to transmit clear 64 kbps channels, thereby enabling voice, fax,
and data transmission.
The Bt8954 with a higher speed DSL bit pump, such as the Bt8970, allows a
greater number of voice conversations to be simultaneously carried over a single
twisted pair. The Bt8954/Bt8970 combination can facilitate up to 18 64-kbps time
slots. If clear channel capability is needed, this combination results in up to
18 (PCM18) systems. When used with 2:1 ADPCM voice compression,
the Bt8954/Bt8970 combination makes up to 36 voice channels possible.
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Conexant
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Bt8954
1.0 DSL Systems
1.1 Voice Pair Gain Applications
Voice Pair Gain Framer
Bt8954’s position among the key elements of a PCM4 (4-channel) voice pair
gain modem is illustrated in Figure 1-1. The Pulse Code Multiplexed (PCM)
codec and Subscriber Line Interface Circuit (SLIC) chips for each channel
perform the transmit encoding (A/D conversion) and receive decoding (D/A
conversion) of voice signals. The time-division multiplexing of the voice signals
on the PCMT and PCMR serial buses is as follows: Bt8954 informs PCM
Codec_n with the PCMFn frame sync when to expect the next byte from Bt8954
on the PCMR bus, and when to put its next byte on the PCMT bus. In this way,
Bt8954 uses the PCMFn frame sync to designate the time slot that Codec_n has
access to the PCMR and PCMT buses.
Figure 1-1. Block Diagram of a PCM4 Voice Pair Gain Modem
PCMCLK
QCLK
Hybrid
Bt8960/70
Bit Pump
BCLK
RDAT
Bt8954
VPG Framer
PCMR
PCMT
TDAT
CODEC1
FSX1/FSR1
SLIC1
C1
C2 DET* E0
PCMF1
.
CODEC4
FSX4/FSR4
SLIC4
C1
C2 DET* E0
PCMF4
Microcomputer
Logic
1.1.1 Repeaters
Figure 1-2 illustrates a pair of Bt8954 repeaters placed in line between Central
Office and remote terminals to extend the transmission distance. For each Bt8954
repeater, the BCLK/QCLK is connected to the BCLK/QCLK of its source
transceiver while the BCLK_REP/QCLK_REP is connected to the BCLK/QCLK
of its destination transceiver. The Central Office Bt8954 gets its
HCLK/BCLK/QCLK from the Central Office transceiver, which generates them
from a free-running crystal. The repeater transceiver connected to the Central
Office recovers its HCLK, BCLK, and QCLK from the HDSL line. These signals
then drive the HCLK, BCLK, and QCLK pins of the Central Office to Remote
Terminal Bt8954, and the HCLK, BCLK_REP, and QCLK_REP pins of the
Remote Terminal to Central Office Bt8954. The repeater transceiver connected to
the Remote Terminal receives HCLK from the repeater transceiver connected to
the Central Office. The repeater transceiver connected to the Remote Terminal
generates BCLK/QCLK and drives the BCLK/QCLK pins of the Remote
Terminal to Central Office Terminal Bt8954. The repeater transceiver drives the
BCLK_REP/QCLK_REP pins of the Central Office Terminal to Remote
Terminal Bt8954.
In Repeater Mode, the Bt8954 does not use the FIFOs. First, data received
from the bit pump is descrambled.
1-2
Conexant
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Bt8954
1.0 DSL Systems
1.1 Voice Pair Gain Applications
Voice Pair Gain Framer
Next, EOC and IND overhead are inserted from the Bt8954 EOC and IND
registers. The CRC is then calculated and inserted. Then the data is scrambled and
transmitted to the destination bit pump.
Bt8954 (C→R) scrambles like Bt8954 in the Central Office terminal but
descrambles like Bt8954 in the remote terminal. That is, SCRAM_TAP = 0
[TCMD2; 0x87.1] but DSCRAM_TAP = 1 [RCMD_2; 0x91.4].
Bt8954 (R→C) scrambles like Bt8954 in the remote terminal but descrambles
like Bt8954 in the Central Office terminal. That is, SCRAM_TAP = 1
[TDMD2; 0x87.1] but DSCRAM_TAP = 0 [RCMD_2; 0x91.4].
Figure 1-2. Repeater Block Diagram
Repeater
Bt8954 (C→R)
Central Office Terminal
Bt8954
TDAT
RDAT
Bt8960/
Bt8970
Bt8960/
Bt8970
BCLK
BCLK_REP
QCLK
QCLK_REP
RDAT
TDAT
Remote Terminal
Bt8960/
Bt8970
HCLK
Bt8960/
Bt8970
Bt8954
RDAT
TDAT
Bt8954 (R→C)
XTAL
TDAT
RDAT
QCLK_REP
QCLK
BCLK_REP
BCLK
XTAL
XTAL
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Conexant
1-3
Bt8954
1.0 DSL Systems
1.1 Voice Pair Gain Applications
Voice Pair Gain Framer
1.1.2 Subscriber Modem
Figure 1-3 illustrates a DSL data modem application where a Central Processing
Unit (CPU) delivers PCM data directly to Bt8954. Alternatively, a multichannel
communications controller such as Bt8472/4 can be used to manage the transfer
of data between the CPU and the PCM channel through a local shared memory.
Figure 1-3. Subscriber Modem (Terminal) System Block Diagram
Single Channel Payload
CPU
PCM Serial
Port
Bt8954
Bit Pump
Memory
Multichannel Payload
CPU
Bt8472/4
PCM
Bt8954
Bit Pump
HDLC Controller
Shared
Memory
PCI
POTS
1-4
CODEC
Conexant
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Bt8954
1.0 DSL Systems
1.2 System Interfaces
Voice Pair Gain Framer
1.2 System Interfaces
System interfaces and associated signals for the Bt8954 functional circuit blocks
are illustrated in Figure 1-4. Circuit blocks are described in the following
sections, and signals are defined in Table 2-1.
Figure 1-4. Bt8954 System Interfaces
PCMT
ADPCMCK
PCMCKO
DSL
PCM
Interface
PCMCKI
Interface
PCMR
BCLK_REP
QCLK_REP
BCLK
QCLK
TDAT
RDAT
PCMF[18:1]
PLL
HCLK
N8954DSC
TCK
TDI
TDO
TMS
MUXED
MOTEL*
WR*/R/W*
RD*/DS*
ALE
CS*
Interface
Access
RST*
AD[7:0]
Microcomputer
ADDR[7:0]
IRQ*
Test
Conexant
1-5
Bt8954
1.0 DSL Systems
1.2 System Interfaces
1-6
Voice Pair Gain Framer
Conexant
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2
2.0 Pin Descriptions
Bt8954 pin assignments for the 68-pin Plastic Leaded Chip Carrier (PLCC)
package are illustrated in Figure 2-1. The functional pinout for the Bt8954 is
illustrated in Figure 2-2, and the signals are defined in Table 2-1.
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
DTEST
HCLK
BCLK_REP
BCLK
RDAT
TDAT
PCMF[18]
PLL_VDD
PLL_GND
PCMF[17]
PCMF[16]
PCMF[15]
PCMF[14]
PCMR
PCMCKI
PCMCKO
VDD
Figure 2-1. Pin Diagram
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Bt8954
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
GND
ADPCMCK
PCMF[13]
PCMF[12]
PCMF[11]
PCMF[10]
PCMF[9]
VDD
GND
PCMF[8]
PCMF[7]
PCMF[6]/EPCMF[6]
PCMF[5]/EPCMF[5]
PCMF[4]/EPCMF[4]
PCMF[3]/EPCMF[3]
PCMF[2]/EPCMF[2]
PCMF[1]/EPCMF[1]
VDD
AD[7]
AD[6]
AD[5]
AD[4]
AD[3]
AD[2]
AD[1]
AD[0]
MOTEL*
MUXED
RST*
TCK
TDO
TDI
TMS
PCMT
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
QCLK
QCLK_REP
CS*
RD*/DS*
WR*/R/W*
ALE
ADDR[6]
VDD
GND
ADDR[5]
ADDR[4]
ADDR[3]
ADDR[2]
ADDR[1]
ADDR[0]
IRQ*
GND
N8954DSC
Conexant
2-1
Bt8954
2.0 Pin Descriptions
Voice Pair Gain Framer
Figure 2-2. Bt8954 Functional Pinout
36
Motorola/Intel I
14
Write*/Read/Write I
15
Address Latch Enable I
37
Interrupt Request I
28-35
Address Data I/O
Address Bus I 16, 19-24
38
Reset I
12
Chip Select I
13
Read/Data Strobe I
MOTEL*
WR*/R/W*
ALE
MUXED
Microcomputer
AD[7:0]
Interface
ADDR[6:0]
RST*
CS*
RD*/DS*
Quaternary Clock
Receive Data
Bit Clock
I
I
I
10
5
6
QCLK
RDAT
BCLK
BCLK Repeater
I
7
BCLK_REP
QCLK Repeater
I
11
QCLK_REP
PCM Transmit Data Input
I
43
PCMT
PCM Clock Input
I
63
PCMCKI
IRQ*
25
TDAT
4
O
Transmit Data
62
59
O
O
PCM Clock Output
64
O
PCM Receive Data Output
OD Interrupt Request
DSL Interface
Repeater Pins
PCMCKO
ADPCMCK
PCMR
PCM Interface
ADPCM Clock Output
44-51
54-58
PCMF[18:1] 65-68,3 O PCM Frame Sync
EPCMFn[6:1] 44-49
8
HCLK
HCLK Input
I
Digital Test
I
9
DTEST
JTAG Test Data In
I
41
TDI
JTAG Test Mode Select
I
TMS
JTAG Test Clock
I
42
39
Power Supply
Power Supply
PLL Power Supply
PLL Ground
O PCM Frame Sync
PLL
Test and Diagnostic
Interface
40
O JTAG Test Data Out
TCK
61, 27 VDD
17, 53 VDD
2
PLL_VDD
1
TDO
Power and
Ground
GND_O 26, 60
GND_IC 18, 52
Ground
I Ground
PLL_GND
I = Input, O = Output,
I/O = Bidirectional, OD = Open Drain
2-2
Conexant
N8954DSC
Bt8954
2.0 Pin Descriptions
Voice Pair Gain Framer
Table 2-1. Hardware Signal Definitions (1 of 4)
Microcomputer Interface (MCI)
Pin Label
Pin
Number
Signal Name
I/O
Definition
MOTEL*
36
Motorola/Intel*
I
Selects between Motorola and Intel handshake conventions
for the RD*/DS* and WR*/R/W* signals.
MOTEL* = 1 for Motorola protocol: DS*, R/W*;
MOTEL* = 0 for Intel protocol: RD*, WR*.
ALE
15
Address Latch Enable
I
Falling-edge-sensitive input. The value of AD[7:0] when
MUXED = 1, or of ADDR[7:0] when MUXED = 0, is internally
latched on the falling edge of ALE.
CS*
12
Chip Select
I
Active-low input used to enable read/write operations on the
Microcomputer Interface (MCI).
RD*/DS*
13
Read/Data Strobe
I
Bimodal input for controlling read/write access on the MCI.
When MOTEL* = 1 and CS* = 0, RD*/DS* behaves as an
active-low data strobe, DS*. Internal data is output on
AD[7:0] when DS* = 0 and R/W* = 1. External data is
internally latched from AD[7:0] on the rising edge of DS*
when R/W* = 0.
When MOTEL* = 0 and CS* = 0, RD*/DS* behaves as an
active-low read strobe RD*. Internal data is output on
AD[7:0] when RD* = 0. Write operations are not controlled
by RD* in this mode.
WR*/R/W*
14
Write/Read/Write
I
Bimodal input for controlling read/write access on the MCI.
When MOTEL* = 1 and CS* = 0, WR*/R/W* behaves as a
read/write select line, R/W*. Internal data is output on
AD[7:0] when DS* = 0 and R/W* = 1. External data is
internally latched from AD[7:0] on the rising edge of DS*
when R/W* = 0.
When MOTEL* = 0 and CS* = 0, WR*/R/W* behaves as
an active-low write strobe, WR*. External data is internally
latched from AD[7:0] on the rising edge of WR*. Read
operations are not controlled by WR* in this mode.
AD[7:0]
28–35
Address-Data[7:0]
I/O
ADDR[6:0]
19–24,
16
Address Bus [6:0]
(Not Multiplexed)
I
Provides a glueless interface to microcomputers with
separate address and data buses. ADDR[6] = MSB, ADDR[0]
= LSB. Usage is controlled using the MUXED signal.
I
Controls the MCI addressing mode.
When MUXED = 1, the MCI uses AD[7:0] as a multiplexed
signal for address and data (typical of Intel processors).
When MUXED = 0, the MCI uses ADDR[7:0] as the
address input and AD[7:0] for data only (typical of Motorola
processors).
O,
OD
Active-low open-drain output that indicate requests for
interrupt. Asserted whenever at least one unmasked interrupt
flag is set. Remains inactive whenever no unmasked
interrupt flags are present.
MUXED
37
Addressing Mode Select
IRQ*
25
Interrupt Request
RST*
38
Reset
N8954DSC
I
Eight-bit bidirectional multiplexed address-data bus.
AD[7] = MSB, AD[0] = LSB. Usage is controlled using the
MUXED signal.
Asynchronous, active-low, level-sensitive input that resets
the framer.
Conexant
2-3
Bt8954
2.0 Pin Descriptions
Voice Pair Gain Framer
Table 2-1. Hardware Signal Definitions (2 of 4)
Repeater Pins
DSL Interface
Pin Label
2-4
Pin
Number
Signal Name
I/O
Definition
BCLK
6
Bit Clock
I
Corresponds to the DSL channel. BCLK operates at the 2B1Q
symbol rate. The rising edge of BCLK outputs 2x TDAT. The
falling edge of BCLK samples QCLK at the RDAT input. (In
the repeater terminal, BCLK is the BCLK from the bit pump to
which RDAT is connected.)
NOTE(S): Refer to Appendix A, page 81.
The BCLK signal from the bit-pump to the channel unit
device is sensitive to overshoot and undershoot. The BCLK
sensitivity could cause bit-errors in the system. A 100 Ω
series terminating resistor might be required to help dampen
the overshoot and undershoot. The bit-pump line cards
include a 74HCT244 to drive the long traces through the
motherboard 96-pin connectors.
QCLK
10
Quaternary Clock
I
Operates at the 2B1Q symbol rate (1/2 bit rate) and identifies
sign and magnitude alignment of both the RDAT and TDAT
serially encoded bit streams.
The falling edge of BCLK samples QCLK: 0 = sign bit;
1 = magnitude bit. In the Repeater Terminal, BCLK is the
BCLK from the bit pump to which RDAT is connected.
TDAT
4
Transmit Data
O
DSL transmit data output at the bit rate on the rising edge of
BCLK. Serially encoded with the 2B1Q sign bit aligned to the
QCLK low level and the 2B1Q magnitude bit aligned to the
QCLK high level.
RDAT
5
Receive Data
I
DSL receive data input sampled on the falling edge of BCLK.
The serially encoded 2B1Q sign bit is sampled when QCLK is
low, and the 2B1Q magnitude bit is sampled when QCLK is
high.
BCLK_REP
7
BCLK from destination
bit pump in a repeater
terminal
I
BCLK from the bit pump to which the Bt8954 TDAT is
connected in a repeater terminal. It is used only in the
repeater mode and should be tied to VDD or GND in
non-repeater terminals.
QCLK_REP
11
QCLK from destination
bit pump in a repeater
terminal
I
QCLK from the bit pump to which the Bt8954 TDAT is
connected in a repeater terminal. It is used only in the
repeater mode and should be tied to VDD or GND in
non-repeater terminals.
Conexant
N8954DSC
Bt8954
2.0 Pin Descriptions
Voice Pair Gain Framer
Table 2-1. Hardware Signal Definitions (3 of 4)
PLL
PCM Interface
Pin Label
Pin
Number
Signal Name
I/O
Definition
PCMCKO
62
PCM Clock Output
O
Output PCM clock for sending and receiving bits from PCM
codecs. It is generated by the PLL and is 1.536 MHz or
2.048 MHz depending on the PLL configuration. Connect to
receive/transmit bit clocks and receive/transmit master
clocks of PCM codecs. In normal operation, tie to PCMCKI.
PCMCKI
63
PCM Clock Input
I
Sends and receives bits from PCM codecs. Controls the PCM
Formatter, reads from the RFIFO, and writes into the TFIFO.
In normal operation, tie to PCMCKO.
ADPCMCK
59
ADPCM Clock Output
O
Used by ADPCM chips. It is 10x or 4x PCMCKO.
PCMFn
3,
44-51,
54-58,
65-68
PCM Frame Sync (n =
1,...,18)
O
Frame sync pulse for receiving bits from and transmitting
bits to a PCM codec. Connect to receive/transmit frame
syncs of the PCM codec. This signal is low if not connected
to any PCM codec. It supports both short-frame and
long-frame operations.
EPCMFn
44-49
Encoded PCM Frame
Sync
(n = 1,...,6)
O
Channel number of bits received from and transmitted to
PCM codecs. Connect to a decoder to generate
receive/transmit frame syncs for PCM codecs. For n = 1,..,6,
EPCMFn is multiplexed with PCMFn depending on the
ENC_FSYNC configuration in the PCM Format register
[PCM_FORMAT; 0xF1.6].
PCMR
64
PCM Receive Data
Output
O
Serial bit stream to PCM codecs is shifted out at the rising
edge of PCMCKI.
PCMT
43
PCM Transmit Data
Input
I
Serial bit stream from the PCM codecs is sampled at the
falling edge of PCMCKI.
HCLK
8
HCLK Input
I
Connects to the HCLK output of the Bt8960/70 bit pump. It is
32xBCLK or 64xQCLK and is used as the PLL clock
reference.
DTEST
9
Digital Test
I
DTEST–Active high test input used by Conexant to enable an
internal test mode. This input should be tied to ground
(GND).
N8954DSC
Conexant
2-5
Bt8954
2.0 Pin Descriptions
Voice Pair Gain Framer
Table 2-1. Hardware Signal Definitions (4 of 4)
Power and Ground
Test and Diagnostic Interface
Pin Label
2-6
Pin
Number
Signal Name
I/O
Definition
TDI
41
JTAG Test Data Input
I
Test data input per IEEE Std 1149.1-1990. Used for loading
all serial instructions and data into internal test logic.
Sampled on the rising edge of TCK. TDI can be left
unconnected if it is not being used because it is pulled up
internally.
TMS
42
JTAG Test Mode Select
I
Test mode select input per IEEE Std 1149.1-1990. Internally
pulled-up input signal that controls the test-logic state
machine. Sampled on the rising edge of TCK. TMS can be left
unconnected if it is not being used because it is pulled up
internally.
TDO
40
JTAG Test Data Output
O
Test data output per IEEE Std 1149.1-1990. Three-state
output used for reading all serial configuration and test data
from internal test logic. Updated on the falling edge of TCK.
TCK
39
JTAG Test Clock
I
Test clock input per IEEE Std 1149.1-1990. Used for all test
interface and internal test-logic operations. If unused, TCK
should be pulled low.
VDD
17,
27,
53,
61
Power Supply
I
Power supply pins for the I/O buffers and core logic
functions.
5 VDC ± 5%.
GND
18,
26,
52,
60
Ground
G
Ground pins for the I/O buffers and core logic functions.
Must be held at the same potential as PLL_GND.
PLL_VDD
2
PLL Power Supply
P
Dedicated supply pin for the PLL circuitry. Connect to VDD
externally.
PLL_GND
1
PLL Ground
G
Dedicated ground pin for the PLL circuitry. Must be held at
the same potential as GND.
Conexant
N8954DSC
3
3.0 Circuit Descriptions
3.1 Overview
Figure 3-1 details the major blocks and pins of Bt8954. After the 2B1Q decode of
the bit stream is received from the DSL bit pump, the Receive Framer detects the
beginning of the Digital Subscriber Line (DSL) frame, and generates the required
pulses for synchronizing the different demultiplexing functions. The Payload
Demux block strips overhead bits from the DSL frame and puts the payload for
the different Pulse Code Multiplexed (PCM) time slots into the PCM RFIFO.
The PCM RFIFO is emptied through the PCMR pin.
On the transmit side, the PCM TFIFO is filled with serial data on PCMT.
Payload data from the TFIFO is multiplexed with signaling data from the
signaling registers and overhead from the OH (overhead) registers. The
multiplexed data is then sent to the DSL bit pump, through the TDAT pin, after
being 2B1Q encoded.
PCM and DSL loopback functions are performed using the loopback blocks.
The PCMCLK, ADPCMCK, and the internal clock are generated and
synchronized to BCLK with the PLL. The PLL uses HCLK as its clock reference.
Figure 3-1. Block Diagram
2B1Q
Decoder
Payload
Demux
PLL
OH/Signaling
Registers
2B1Q
Encoder
Payload
Mux
PCM
RFIFO
HCLK
BCLK
LB
LB
QCLK
TDAT
ADPCMCK
PCMCLK
PCMF[18:1]
PCMT
Microcomputer Interface
ADDR[7:0]
AD[7:0]
MUXED
ALE
WR/RW*
CS*
DS*
MOTEL*
IRQ*
RST*
Transmitter
PCM
TFIFO
PCMR
ADPCM/PCM Codecs
DSL Bit-Pump
RDAT
Receive
Framer
PCM Formatter
Receiver
Microcomputer
N8954DSC
Conexant
3-1
Bt8954
3.0 Circuit Descriptions
3.2 DSL Frame Format
Voice Pair Gain Framer
3.2 DSL Frame Format
The DSL frame is the fundamental data element of the bit streams transmitted and
received by Bt8954 at the DSL interface. It is patterned after the 2 T1, 2 E1, and
3 E1 frame structures. Figure 3-2 illustrates the basic format of a DSL frame.
Figure 3-2. Basic DSL Frame Format
0 ms
6 ms
DSL Frame
#Quats = 4 x (48N + 6S) + 24 = 192N + 24S + 24
#Bits = 2 x (192N + 24S + 24)
Bit Rate (kbps) = 2 x (192N + 24S + 24) = (64N + 8S + 8)
6 ms
7Q
S S
t t
q q
1 2
1Q
12x(4N+0.5S)
Sync D B B
Word O 0 0
H 1 2
5Q
5Q
B D B B
1 O 1 1
2 H 3 4
B D B B
2 O 2 2
4 H 5 6
5Q
1Q 1Q
S S
B
t t
4
q q
8 1 2
B D B B
3 O 3 3
6 H 7 8
“6-”
1/(32N + 4S + 4) ms
S-Bits
Byte1
Byte2
Byte3
0-8 Bits 8 Bits
Sync
Word
“6+”
Byte_N
LEGEND:
Bnn
#Quats = (4N + 0.5S)
#Bits = 2 x (4N + 0.5S)
Bnn = Payload Blocks 1-48
DOH = DSL Overhead
S-bits = Data Signaling Bits
N = # of Voice Channels
3.2.1 Detailed Frame Structure
Each frame has a 6 ms duration and is made up of 48 payload blocks. Each block
contains S number of S-bits (for data signaling) and N number of bytes where N
is the number of PCM time slots. The microcomputer selects the number of S-bits
in the NUM_SBITS [3:0] field of Transmit Command register 2
[TCMD_2; 0x87.5:2] and the N number of PCM time slots in the NUM_
CHAN[4:0] field of the PCM Format register [PCM_FORMAT; 0xF1.4:0]. S-bits
vary from 0 to 8 bits, while N varies from 1 to 18 time slots. Groups of 12 payload
blocks are concatenated, and each group is separated by an ordered set of DOH
(DSL overhead) bits. A 14-bit SYNC word pattern identifies the beginning of the
DSL frame.
Forty-eight overhead bits are defined in one DSL frame with the last 2 bits
used for stuffing. This corresponds to an 8 kbps (48 bits/6 ms) overhead bit rate.
The 2 bits of stuffing are the average number of stuffing bits per frame since the
transmitter alternatively transmits 0 bits of stuffing or 4 bits of stuffing in each
frame.
3-2
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.2 DSL Frame Format
Voice Pair Gain Framer
3.2.2 Differences Between the DSL and HDSL T1/E1 Frame Formats
The DSL frame format is similar to the T1/E1 frame formats that are transported
on one HDSL loop. The main difference is due to the number of S-bits. While
fixed as 1 F-bit/block and 1 Z-bit/block for the T1 and E1 HDSL frame formats, it
can vary between 0 and 8 bits for the DSL frame format. The number of S-bits is
allowed to vary up to 8 bits so that a variable number of D-channel bit rates (up to
64 kbps) can be supported.
3.2.2.1 EXTRA_Z_BIT
Option
Some systems (e.g., PCM11) require an extra 8 kbps Z-bit field in addition to the
basic frame structure outlined in Figure 3-2. To accommodate such systems, each
block of the DSL frame has an extra Z-bit (preceding the S-bits field) that can be
enabled for transmit when EXTRA_Z_BIT in Command register 1
[CMD_1; 0xC0.5] is set. For example, a PCM11 system can have a 784 kbps bit
rate consisting of 704 kbps (11x64 kbps) of payload, 8 kbps of overhead, 64 kbps
of signaling information, and 8 kbps of the extra Z-bit. This extra Z-bit field is a
dummy field and is not accessible through the MC.
3.2.3 Overhead Bit Allocation
The overhead bit allocation of the DSL frame is the same as that of the HDSL
frame given in Table 3-1.
Table 3-1. DSL Frame Structure and Overhead Bit Allocation (1 of 2)
DOH Bit
Number
Symbol
1–14
SW1–SW14
15
losd
Loss of Signal
IND[12]
16
febe
Far End Block Error
IND[11]
Bit Name
SYNC Word
DOH Register Bit
—
Payload Blocks 1–12
17–20
eoc1–eoc4
Embedded Operations Channel
EOC[12]–EOC[9]
21–22
crc1–crc2
Cyclic Redundancy Check
23
ps1
HTU-R Power Status
IND[10]
24
ps2
Power Status Bit 2
IND[9]
25
bpv
Bipolar Violation
IND[8]
26
eoc5
Embedded Operations Channel
EOC[8]
—
Payload Blocks 13–24
N8954DSC
27–30
eoc6–eoc9
Embedded Operations Channel
31–32
crc3–crc4
Cyclic Redundancy Check
33
hrp
HDSL Repeater Present
IND[7]
34
rrbe
Repeater Remote Block Error
IND[6]
35
rcbe
Repeater Central Block Error
IND[5]
36
rega
Repeater Alarm
IND[4]
Conexant
EOC[7]–EOC[4]
—
3-3
Bt8954
3.0 Circuit Descriptions
3.2 DSL Frame Format
Voice Pair Gain Framer
Table 3-1. DSL Frame Structure and Overhead Bit Allocation (2 of 2)
DOH Bit
Number
Symbol
Bit Name
DOH Register Bit
Payload Blocks 25–36
37–40
eoc10–eoc13
Embedded Operations Channel
41–42
crc5–crc6
43
rta
Remote Terminal Alarm
IND[3]
44
rtr
Ready to Receive
IND[2]
45
uib
Unspecified Indicator Bit
IND[1]
46
uib
Unspecified Indicator Bit
IND[0]
Cyclic Redundancy Check
EOC[3]–EOC[0]
—
Payload Blocks 37–48
3-4
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.3 Receiver
Voice Pair Gain Framer
3.3 Receiver
The receiver performs SYNC word detection, overhead extraction, descrambling
of payload data, error performance monitoring, and payload mapping of DSL data
from the received DSL frame into the PCM RFIFO. Figure 3-3 illustrates the
receiver block diagram. The receiver consists of the 2B1Q decoder, receive
framer, descrambler, CRC check, and payload demux.
Figure 3-3. Receiver Block Diagram
Receive Framer
Sync
Detector
State
CNT
STUFF
Detector
BCLK
QCLK
RDAT
RDSL_6ms
2B1Q
Decoder
TDAT
CRC
CHK
Payload
Demux
0
RDAT_DESCR
Descrambler
1
PCM
RFIFO
PD_LOOP
3.3.1 2B1Q Decoder
The 2 Binary, 1 Quaternary (2B1Q) decoder provides the capability to connect
directly to the Bt8960/70 DSL transceivers. The 2B1Q decoder samples and
aligns the incoming sign and magnitude data. Refer to Table 3-2 for 2B1Q
mapping.
Table 3-2. 2B1Q Decoder Alignment
N8954DSC
First Bit
(Sign)
Second Bit
(Magnitudes)
Quaternary Symbol
(Quat)
1
0
+3
1
1
+1
0
1
–1
0
0
–3
Conexant
3-5
Bt8954
3.0 Circuit Descriptions
3.3 Receiver
Voice Pair Gain Framer
3.3.2 Receive Framer
The receive framer generates the RDSL_6ms pulse after detecting the SYNC
WORD. RDSL_6ms generates pointers that control overhead extraction in the
CRC and OH demux circuitry. The MC initializes the framer to the OUT_OF
SYNC state by writing any data value to SYNC_RST [0xD8]. From the OUT_OF
SYNC state, the framer advances to SYNC_ACQUIRED when the SYNC word is
detected. The framer searches all bits received on RDAT to locate a match with
the SYNC word pattern, SYNC_WORD [0xA1].
Due to the possibility of Tip/Ring connector reversal, all sign bits received on
RDAT might be inverted. Therefore, the receive framer searches for both the
programmed SYNC word value and the sign-inverted SYNC word value.
Consequently, a maximum of two values of the SYNC word are used in finding
the frame location. If the SYNC word detected is a sign-inverted version of the
configured SYNC word, the framer sets the Tip/Ring Inversion [TR_INVERT]
status bit of the Receive Status 1 register [RSTATUS_1; 0xE5.6] and
automatically inverts the sign of all quats received on RDAT.
After detecting the SYNC WORD and changing to the SYNC_ACQUIRED
state, the framer progresses through a programmable number of intermediate
SYNC_ACQUIRED states before entering the IN_SYNC state. In each
SYNC_ACQUIRED state, the framer searches for the previously detected SYNC
word value in one of two locations based upon the absence or presence of the four
STUFF bits (detected by the STUFF Detector). If the SYNC word is detected in
one of the two possible locations, the STATE_CNT[2:0] counter is incremented
[RSTATUS_2; 0xE6.2:0]. When STATE_CNT[2:0] increments to the value
selected by the REACH_SYNC[2:0] criteria [RCMD_1; 0x90.2:0], the framer
changes to the IN_SYNC state. During the SYNC_ACQUIRED state, if valid
SYNC is not detected at one of the two possible locations, the framer returns to
the OUT_OF_SYNC state as illustrated in Figure 3-4.
Figure 3-4. Receive Framer Finite State Machine
Consecutive SYNC_ACQUIRED states per REACH_SYNC criteria
1
2
3
4
5
6
7
8
SYNC
SYNC
NO SYNC
SYNC
OUT_OF
SYNC
IN_SYNC
NO
SYNC
SYNC
NO SYNC
NO SYNC
8
7
6
5
4
3
2
1
Consecutive SYNC_ERRORED states per LOSS_SYNC criteria
3-6
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.3 Receiver
Voice Pair Gain Framer
After entering IN_SYNC, the framer either remains IN_SYNC as successive
SYNC words are detected or regresses to the SYNC_ERRORED state if SYNC
pattern errors are found. During SYNC_ERRORED states, the number of
matching bits from each comparison of received SYNC word and the
programmed SYNC word pattern must meet or exceed the programmed pattern
match tolerance specified by THRESH_CORR [RCMD_2; 0x91.3:0]. If the
number of matching bits falls below tolerance, the framer expands the locations
searched to quats on either side of the expected location, as illustrated in
Figure 3-5. After detecting a SYNC pattern error and changing to the
SYNC_ ERRORED state, the framer passes through a programmable number of
intermediate SYNC_ERRORED states, before entering the OUT_OF SYNC
state. STATE_CNT increments for each frame in which SYNC is not detected
until the count reaches the LOSS_SYNC[2:0] criteria [RCMD_1; 0x90.5–3] and
the framer enters the OUT_OF SYNC state. If at any time during the
SYNC_ERRORED state the framer detects a completely correct SYNC word
pattern at one of the valid frame locations, then framer returns to the IN_SYNC
state. The ETSI standard, for HDSL transport, recommends the
REACH_SYNC = 2 and LOSS_SYNC = 6 framing criteria.
Figure 3-5. Threshold Correlation Effect on Expected SYNC Locations
SYNC Pattern ≥ THRESH_CORR
SYNC_ERRORED
SYNC_ERRORED
1
2
–1q
+1q
–1q
SYNC_ERRORED
3
+1q
–1q
+1q
t
0
6 ms
12 ms
18 ms
SYNC Pattern < THRESH_CORR
SYNC_ERRORED
1
–2q
SYNC_ERRORED
2
–3q –1q
+2q
SYNC_ERRORED
3
–4q –2q
+1q +3q
+2q +4q
t
0
6 ms
12 ms
18 ms
q = 2 bits = 1 quat
= Search Location
3.3.3 CRC Check
The CRC Check block calculates a CRC value for every received DSL frame. The
CRC Check block reports an error if the CRC in the current frame (calculated at
the other end’s transmitter) does not match the CRC that was calculated for the
previous DSL receive frame. Individual DSL block errors are reported in the
CRC_ERROR bit of the Receive Status 2 register [RSTATUS_2; 0xE6.5] and
accumulated in the CRC Error Count register [CRC_CNT; 0xE8]. The CRC
calculation in the receiver is exactly the same as that in the transmitter.
N8954DSC
Conexant
3-7
Bt8954
3.0 Circuit Descriptions
3.3 Receiver
Voice Pair Gain Framer
3.3.4 Descrambler
The MC enables the descrambler by setting DSCRAM_EN bit of the Receive
Command register and selects the descrambler algorithm via the DSCRAM_TAP
[RCMD_2; 0x91.5,4]. The descrambler, if enabled, descrambles all DSL receive
data except the SYNC word. The algorithm is chosen from one of two possible
choices, depending on whether Bt8954 is located at the Central Office or at a
Remote Site.
The descrambler is basically a 23-bit-long Linear Feedback Shift register
(LFSR). The algorithm chosen determines the feedback points. The LFSR
structure and polynomials for the two descrambler algorithms are illustrated in
Figure 3-6 and Figure 3-7. The descrambler is clocked with BCLK.
Figure 3-6. LFSR Structure for Transmission in the Remote → Central Office Direction
Scrambled Input (b )
k
Unscrambled Output (ck)
+
z-1
x
x
x
z-1
k-16
x
z-1
k-1
z-1
k-2
x
z-1
k-15
x
z-1
x
z-1
x
z-1
k-14
k-17
x
z-1
k-3
x
z-1
k-13
z-1
k-18
k-4
z-1
x
z-1
k-12
z-1
x
k-11
z-1
x
k-20
x
x
k-19
x
k-5
k-6
z-1
x
z-1
k-21
x
z-1
z-1
z-1
x
k-9
k-22
z-1
x
k-7
k-10
z-1
x
x
k-8
z-1
x
k-23
+
Polynomial: ck = xk-23
+
xk-18
b
+
+
k
z-1
= Modulo-2 Summation (XOR gate)
= Delay Element (D flip-flop clocked with BCLK)
Figure 3-7. LFSR Structure for Transmission in the Central Office → Remote Direction
Scrambled Input (b )
k
Unscrambled Output (ck)
+
z-1
x
k-16
x
z-1
k-1
x
z-1
z-1
k-15
x
k-17
x
z-1
k-2
x
z-1
z-1
k-14
x
k-18
x
x
x
z-1
z-1
k-4
z-1
k-3
x
k-13
k-19
z-1
z-1
x
k-5
x
z-1
k-12
x
z-1
k-20
x
z-1
x
z-1
k-11
z-1
k-6
x
k-21
z-1
x
k-7
x
z-1
k-10
z-1
x
k-22
z-1
x
k-8
x
z-1
k-9
z-1
x
k-23
+
Polynomial: ck = xk-23
+
xk-5
+
b
+
k
= Modulo-2 Summation (XOR gate)
z-1 = Delay Element (D flip-flop clocked with BCLK)
3-8
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.3 Receiver
Voice Pair Gain Framer
3.3.5 Payload Demux
The Payload Demux block extracts the Indicator (IND), Embedded Operations
Channel (EOC), and the S-bits from each receive frame and places them in
microcomputer-accessible registers:
•
•
•
Receive Indicator Bits [RIND 0xE2, 0xE3]
Receive Embedded Operations Channel [REOC 0xE0, 0x61]
Receive Signaling FIFOs [RSFIFO_O; 0xE4]
Double-buffering is used to ensure that the OH and signaling information read
by the microcomputer is not corrupted by newly arriving data. The
microcomputer must read the contents of the OH registers within 6 ms for every
frame; otherwise the data is overwritten with new received data. The
microcomputer must read the contents of the RSFIFO_O register within 6 ms, 3
ms, 2 ms, or 1 ms, depending on the EXTRA_SIG_UPDATE configuration bits
that are programmed in Command register 1 [CMD_1; 0xC0].
N8954DSC
Conexant
3-9
Bt8954
3.0 Circuit Descriptions
3.4 Transmitter
Voice Pair Gain Framer
3.4 Transmitter
The transmitter muxes payload data from the PCM channel with overhead and
signaling data into serially encoded 2B1Q data that is sent to the bit pump through
the TDAT pin. Figure 3-8 details the transmitter block diagram, which consists of
Overhead (OH) registers, the Payload Mux, and the 2B1Q Encoder.
Figure 3-8. Transmitter Block Diagram
S-BIT
IND
EOC
CRC REG
OH/Signaling
Registers
CRC
Payload
MUX
PCM
TFIFO
1
0
4-level 1
Scrambler
SYNC
Word
QCLK BCLK
1
2B1Q
Encoder
TDAT
0
RDAT_DESCR
DD_LOOP
= Command Register Bit
Stuff
SCRAM_EN
3.4.1 OH/Signaling Registers
The OH/Signaling registers are the S-Bits, IND, EOC, CRC, and SYNC word
registers. Refer to the Overhead Bit Allocation section, Table 3-1, for the OH bit
positions in the DSL transmit frame. The OH/Signaling registers are accessible by
the microcomputer for writing and reading.
3-10
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.4 Transmitter
Voice Pair Gain Framer
3.4.2 Transmit Signaling FIFOs
Using two sets of transmit signaling FIFOs (TSFIFO_I and TSFIFO_O), double
buffering ensures that the MC has enough time to write new signaling
information without corrupting the signaling information being transmitted, as
illustrated in Figure 3-9.
Figure 3-9. Double Buffering, Using Transmit S-Bits Registers
Blocks In DSL Frame S
TSFIFO Output Regs
Block1
Payload
Block2
Payload
S
Block48
Payload
TSFIFO_O[48]
TSFIFO_O[1] TSFIFO_O[2]
LD
LD
LD
TSFIFO_I[1]
TSFIFO_I[2]
TSFIFO_I[48]
LD_TSIG
TSFIFO Input Regs
S
µComputer
LD_TSIG
MC Loads TSFIFO_I REGS
DSL_SUBFRAME_N (6 ms, 3 ms, 2 ms, 1 ms)
TSFIFO_I→
TSFIFO_O
Transmit TSFIFO_O REGS
DSL_SUBFRAME_N+1 (6 ms, 3 ms, 2 ms, 1 ms)
The MC loads the TSFIFO_I registers after receiving the LD_TSIG interrupt.
In the default case, LD_TSIG is the same as the DSL 6 ms receive frame interrupt
that occurs upon the arrival of the 6 ms DSL frame. The LD_TSIG interrupt can
be made to occur more frequently than 6 ms by programming non-00 values in
the EXTRA_SIG_UPDATE bits in the CMD_1 register [0xC0]. Six, three, two,
or one millisecond(s) later, TSFIFO_I registers are loaded into TSFIFO_O
registers at the next LD_TSIG. TSFIFO_O, which is then transmitted, is not
thereby corrupted by the new TSFIFO_I values being written by the MC during
the next interval.
3.4.3 Payload Mux
The Payload Mux multiplexes the overhead bits from the OH registers, payload
data from the PCM TFIFO, the SYNC word and the CRC bits that were calculated
for the previous transmit frame.
N8954DSC
Conexant
3-11
Bt8954
3.0 Circuit Descriptions
3.4 Transmitter
Voice Pair Gain Framer
3.4.4 CRC Calculation
The CRC calculation is performed on all transmit data, and the Payload Mux
inserts the resulting 6-bit CRC into the subsequent output frame. CRC is
calculated over all bits in the (N)th frame except the SYNC WORD, STUFF, and
CRC bits and then is inserted into the (N+1) frame. The MPU can choose to inject
CRC errors on a per-frame basis by setting the ICRC_ERR bit [TCMD_1;
addr 0x86.1]. The six CRC bits are calculated as follows:
All bits of the (N) frame — except the 14 SYNC and 6 CRC bits, for a total
of M bits — are used in order of occurrence to construct a polynomial in X
such that bit 0 of the (N) frame is the coefficient of the term XM-1 and bit
M-1 of the (N) frame is the coefficient of the term X0.
2. The polynomial is multiplied by the factor X6, and the result is divided,
modulo 2, by the generator polynomial X6 ⊕X⊕1. Coefficients of the
remainder polynomial are used, in order of occurrence, as an ordered set of
check bits, CRC1–CRC6, for the (N+1) frame. Ordering is such that the
coefficient of term X5 in the remainder polynomial is check bit CRC1, and
the coefficient of term X0 is check bit CRC6.
3. Check bits CRC1–CRC6 contained in a frame are associated with the
contents of the preceding frame. When there is no immediately preceding
frame, check bits may be assigned any value.
1.
3.4.5 Scrambler
The MC enables the scrambler by setting SCRAM_EN [TCMD_1; 0x86.0] and
selects the descrambler algorithm via SCRAM_TAP [TCMD_2; 0x87.2]. The
scrambler, if enabled, scrambles all DSL transmit data except the SYNC word and
STUFF bits. The algorithm is chosen from one of two possible choices,
depending on whether Bt8954 is located at the Central Office or at a Remote Site.
Scrambler Algorithms: The scrambler is basically a 23-bit-long Linear
Feedback Shift register (LFSR). The algorithm chosen determines the feedback
points. The LFSR structure and polynomials for the two scrambler algorithms are
illustrated in Figure 3-10 and Figure 3-11.
Figure 3-10. LFSR Structure for Transmission in the Remote → Central Office Direction
Unscrambled Input (B )
k
+
z-1
x
k-16
Scrambled Output (ck)
x
k-1
x
z-1
z-1
x
k-2
k-15
z-1
z-1
Polynomial: ck = xk-23
+
xk-18
z-1
x
k-3
z-1
k-14
z-1
x
k-13
z-1
x
k-18
z-1
x
k-17
+
x
x
b
k
+
k-4
z-1
x
k-19
+
z-1
3-12
z-1
x
x
k-5
z-1
k-12
z-1
x
k-20
z-1
x
x
k-6
z-1
k-11
z-1
x
k-21
z-1
x
x
z-1
z-1
x
k-9
k-22
z-1
k-10
k-7
z-1
x
x
k-8
z-1
x
k-23
= modulo-2 summation (XOR gate)
= Delay Element (D flip-flop clocked with BCLK)
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.4 Transmitter
Voice Pair Gain Framer
Figure 3-11. LFSR Structure for Transmission in the Central Office → Remote Direction
Scrambled Input (b )
k
+
z-1
x
k-16
Unscrambled Output (ck)
x
z-1
k-1
x
z-1
x
z-1
k-2
k-15
z-1
z-1
x
k-17
x
x
k-3
k-14
z-1
z-1
x
k-18
x
k-4
z-1
x
k-13
z-1
z-1
x
k-19
x
z-1
k-5
x
k-12
z-1
z-1
x
k-20
x
z-1
k-6
x
k-11
z-1
x
z-1
k-21
z-1
x
k-10
z-1
x
k-7
z-1
x
k-22
z-1
x
k-9
z-1
x
k-8
z-1
x
k-23
+
Polynomial: ck = xk-23
+
xk-5
+
b
k
+
= modulo-2 summation (XOR gate)
z-1 = Delay Element (D flip-flop clocked with BCLK)
3.4.6 2B1Q Encoder
The 2B1Q encoder converts the data to be transmitted to the bit pump into sign
and magnitude data according to the quaternary alignment provided on the QCLK
input. Table 3-3 depicts how sign and magnitude bits generate 2B1Q coded
outputs on TDAT.
Table 3-3. 2B1Q Encoder Alignment
N8954DSC
First Input Bit
(Sign)
Second Input Bit
(Magnitude)
Quaternary Symbol
0
0
–3
0
1
–1
1
1
+1
1
0
+3
Conexant
3-13
Bt8954
3.0 Circuit Descriptions
3.5 PCM Formatter
Voice Pair Gain Framer
3.5 PCM Formatter
The PCM formatter shifts out the PCMR data at the rising edge of PCMCKI,
samples the PCMT data at the falling edge of PCMCKI, and generates the PCM
frame SYNC signals based on the PCM Format Configuration register [0xF1] as
illustrated in Figure 3-12. The PCM formatter supports direct connection to
popular PCM codecs. Because the formatter generates only one frame SYNC
signal for each PCM codec, codecs like the Texas Instruments TP3054A that have
two frame SYNC signals (FSX for transmit and FSR for receive) must have both
frame SYNCs tied before being connected to the Bt8954.
Figure 3-12. PCM Formatter Detail
PCM
TFIFO
PCMR
ADPCMCK
PCMCKO
PCMCKI
PCMF[18:1]
PCM Codecs
PCM Formatter
PCM
RFIFO
PCMT
All time slots carry clear voice or compressed voice channels depending on
the COMPRESSED bit configuration in the PCM Format register [0xF1.5]. Only
2:1 ADPCM compression is allowed. Therefore, a 64 kbps time slot is carrying
either 2 x 32 kbps of compressed voice or 64 kbps or clear voice. The Bt8954 has
a maximum capacity of 18 clear or 36 compressed voice channels.
The frame SYNCs are in an encoded or decoded form depending on the
ENC_FSYNC bit configuration in PCM_FORMAT [0xF1.6]. If ENC_FSYNC is
reset, the PCM formatter can generate up to 18 frame SYNCs (PCMF[18:1]). In
this case, the frame SYNCs of all the unused time slots are held low. For example,
for a PCM4 system, PCMF[4:1] are active but PCMF[18:5] are held low.
If ENC_FSYNC is set, the PCM formatter generates the frame SYNCs in the
Encoded_Frame_SYNC mode, driving the channel numbers through
EPCMF[6:1], but holding PCMF[18:7] low. Externally, decoders can be used to
generate frame SYNCs from the channel numbers.
The period of PCMF[18:1] or EPCMF[6:1] for clear channels is 8 times the
PCMCKI period, while the period for compressed channels is 4 times the
PCMCKI period.
3-14
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.5 PCM Formatter
Voice Pair Gain Framer
The PCMF[18:1] (EPCMF[6:1]) waveforms for various scenarios are
illustrated in Figure 3-13.
Figure 3-13. PCMF [18:1] Waveforms for Encoded and Decoded Frame SYNC Modes
1) PCM2: 2 Clear Channels
PCMCKI
(2.048 MHz)
PCMF1
PCMF2
PCMF[18:3]
Time Slot 1
PCMT/
PCMR
30 Unused Timeslots
Time Slot 2
BYTE1
BYTE2
BYTE1
3.9056µs
2) PCM18: 18 Clear Channels
PCMCKI
(2.048 MHz)
125µs
PCMF1
PCMF18
14 Unused
Time Slots
PCMT/
PCMR
BYTE1
BYTE2
BYTE17
BYTE1
BYTE18
3) ADPCM36: 18 Compressed Channels
PCMCKI
(2.048 MHz)
EPCMF[6:1]
[00 0001]
[00 0010]
[00 0011]
[10 0011]
[10 0100]
[00 0000]
[00 0001]
[0000 0000 0000]
PCMF[18:7]
PCMT/
PCMR
[10 0010]
BYTE1[7:4]
BYTE1[3:0]
BYTE2[7:4]
BYTE17[3:0]
BYTE18[7:4]
BYTE18[3:0]
BYTE1[7:4]
NOTE(S): SYNC_WIDTH (PCM_FORMAT_4) = 0001; FSYNC2BYTE (PCM_FORMAT_4) = 0001.
N8954DSC
Conexant
3-15
Bt8954
3.0 Circuit Descriptions
3.6 Loopbacks
Voice Pair Gain Framer
3.6 Loopbacks
Bt8954 provides multiple PCM and DSL loopbacks as illustrated in Figure 3-14.
The output towards which data is looped is called the test direction. Loopback
activation in the test direction does not disrupt the through-data path in the
non-test direction. Table 3-4 lists the loopback controls which are designated by
initials corresponding to test direction and the channel from which data is looped.
Figure 3-14. PCM and DSL Loopbacks
DSL Channel
PCM Channel
RDAT
PCMR
DD_LOOP
PD_LOOP
DP_LOOP
PP_LOOP
PCMT
TDAT
Table 3-4. PCM and DSL Loopbacks
Loopback
Command Register
Test Direction
PP_LOOP
CMD_1; 0xC0
Receive
PCM Loopback on PCM Side
DP_LOOP
CMD_1; 0xC0
Transmit
DSL Loopback on PCM Side
PD_LOOP
RCMD_2; 0x91
Receive
PCM Loopback on DSL Channel
DD_LOOP
TCMD_2; 0x87
Transmit
DSL Loopback on DSL Channel
3-16
Loopback Description
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.7 Synchronization
Voice Pair Gain Framer
3.7 Synchronization
All signals are synchronized to TDSL_6ms, RDSL_6ms, TPCM_6ms, and
RPCM_6ms. All status registers are synchronized to either TDSL_6ms or
RDSL_6ms. The transmitter signals at the DSL (PCM) interface are synchronized
to TDSL_6ms (TPCM_6ms). The receiver signals at the DSL (PCM) interface are
synchronized to RDSL_6ms (RPCM_6ms). The main contributor to the phase
differences between the DSL_6ms and PCM_6ms signals is that while data is
received and transmitted in a bursty fashion at the PCM interface, it is received
and transmitted in a continuous fashion at the DSL interface.
The detailed relationship between the DSL_6ms and PCM_6ms signals
depends on whether the framer is at the Central Office (COTF) or at the Remote
Site (RTF). Even though TPCM_6ms and RPCM_6ms may not be phase-aligned,
TFIFO and RFIFO provide sufficient data buffering for PCMF to mark coincident
PCM receive and transmit 125 µs frame boundaries. The synchronization
between COTF and RTF is illustrated in Figure 3-15.
Figure 3-15. COTF and RTF Synchronization
RT Framer
COT Framer
TPCM_6 ms
(Master)
RPCM_6 ms
(Slave)
Transmitter.COT
Receiver.COT
TDSL_6 ms
(Slave)
RDSL_6 ms
(Master)
Variable
Path
Delay
RDSL_6 ms
(Master)
Receiver.RT
RPCM_6 ms
(Slave)
TDSL_6 ms
(Slave)
Transmitter.RT
TPCM_6 ms
(Master)
RPCM_6 ms!= TPCM_6 ms
RPCM_6 ms = TPCM_6 ms
3.7.1 COTF Transmitter Synchronization
In the COTF, TPCM_6 ms is always a free-running 6 ms-period signal. At the
Central Office, the DSL transmit frames are slaved to the PCM frame timing. As
illustrated in Figure 3-16, TDSL_6 ms is a 6 ms-period signal that is phase-offset
from TPCM_6ms by TFIFO_WL.COT (TFIFO Water Level in the COTF).
TFIFO_WL.COT determines the amount of PCM data written into the TFIFO
before the transmitter begins extracting DSL frames from the TFIFO.
Figure 3-16. COTF Transmitter Synchronization
6 ms
TPCM_6 ms
6 ms
TDSL_6 ms
TFIFO_WL.COT
N8954DSC
Conexant
3-17
Bt8954
3.0 Circuit Descriptions
3.7 Synchronization
Voice Pair Gain Framer
3.7.2 RTF Receiver Synchronization
The RDSL_6 ms signal in the RTF is generated after SYNC_WORD has been
detected on RDAT. As illustrated in Figure 3-17, RPCM_6 ms is phase-offset
from RDSL_6ms by RFIFO_WL.RT (RFIFO Water Level in the RTF). The PCM
receive frames are slaved to the DSL receive frame timing at the Remote Site.
Figure 3-17. RTF Receiver Synchronization
SYNC_WORD
SYNC_WORD
6 ms
RDAT
RDSL_6 ms
6 ms
RPCM_6 ms
RFIFO_WL.RT
3.7.3 RTF Transmitter Synchronization
In the RTF, the RPCM_6 ms and TPCM_6 ms signals are the same because the
same PCM frame SYNC is used for transmitting and receiving PCM frames from
the PCM codecs. As illustrated in Figure 3-18, TDSL_6ms is phase-offset from
TPCM_6 ms by TFIFO_WL.RT (TFIFO Water Level in the RTF). The DSL
transmit frames are slaved to the PCM transmit frame timing, which in turn is
slaved to the DSL receive frame timing at the Remote Site.
TFIFO_WL.RT = TFIFO_WL.COT.
Figure 3-18. RTF Transmitter Synchronization
6 ms
TPCM_6 ms
6 ms
TDSL_6 ms
TFIFO_WL.RT = TFIFO_WL.COT
3-18
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.7 Synchronization
Voice Pair Gain Framer
3.7.4 COTF Receiver Synchronization
The RDSL_6ms signal in the COTF is generated after SYNC_WORD has been
detected as illustrated in Figure 3-19. RPCM_6ms is phase-offset from
RDSL_6ms by RFIFO_WL.RT (RFIFO Water Level in the RTF) plus time to
realign to the next TPCM_125 µs. At the Central Office, the PCM receive frames
are slaved to the DSL frame timing and aligned to the transmit PCM_125 µs
frame. The re-alignment time is added because the same PCM frame SYNC
signal is used for transmitting and receiving PCM frames from the PCM codecs.
Figure 3-19. COTF Receiver Synchronization
SYNC_WORD
SYNC_WORD
6 ms
RDAT
RDSL_6 ms
125 µs
125 µs
TPCM_125 µs
6 ms
RPCM_6 ms
RFIFO_WL.RT
Realign to
TPCM_125 µs
3.7.5 Round Trip Delay
The microcomputer determines the round-trip delay by measuring the time that
elapses between the Tx and Rx interrupts in the Interrupt Status register
[ISR; 0xD0] at the Central Office.
N8954DSC
Conexant
3-19
Bt8954
3.0 Circuit Descriptions
3.8 Microcomputer Interface
Voice Pair Gain Framer
3.8 Microcomputer Interface
The microcomputer interface (MCI) port (Figure 3-20) configures and controls
operating modes, manages overhead protocol, and reads status information from
Bt8954. In addition, Bt8954 may signal its need for attention from the
microcomputer (MC) by requesting an interrupt. The port can be directly
connected to common MCs like the Motorola 68302 or the Intel 8051.
Figure 3-20. MCI Port
ADDR[6:0]
AD[7:0]
MUXED
ALE
WR/RW*
CS*
MOTEL*
IRQ*
RST*
DS*
Microcomputer Interface
Microcomputer
3-20
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.8 Microcomputer Interface
Voice Pair Gain Framer
3.8.1 Microcomputer Read/Write
The MCI provides access to a 128-byte internal address space. Figure 3-21
depicts the read/write controls. The MCI uses either an 8-bit-wide multiplexed
address-data bus (Intel style) or one 8-bit-wide data bus and another separate
7-bit-wide address bus (Motorola style) for external data communications. The
interface is configured with the inputs, MOTEL* and MUXED. MOTEL* low
selects Intel-type microcomputer and control signals: ALE, CS*, RD*, WR*.
MOTEL* high selects Motorola-type microcomputer and control signals: ALE,
CS*, DS*, R/W*. MUXED high configures the interface to use the multiplexed
address-data bus with both the address and data on the AD[7:0] pins. MUXED
low configures the interface to use separate address and data buses with the data
on the AD[7:0] pins and the address on the ADDR[6:0] pins.
Figure 3-21. Functional Diagram of the Read and Write Controls
ALE
MUXED
ADDR[7:0]
Address
AD[7:0]
MOTEL*
To Registers
RD*/DS*
From Registers
Read Strobe
WR*/R/W*
Write Strobe
CS*
3.8.1.1 Multiplexed
Address/Data Bus
The timing for a read or write cycle is stated in Chapter 5.0, Electrical and
Mechanical Specifications . During a read operation, an external microcomputer
places an address on the address-data bus which is then latched on the falling
edge of ALE. Data is placed on the address-data bus after CS* and RD* (or DS*)
go low. The read cycle is completed with the rising edge of CS* and RD* (or
DS*).
A write operation latches the address from the address-data bus at the falling
edge of ALE. The microcomputer places data on the address-data bus after CS*
and WR* (or DS*) go low. Motorola MCI has R/W* falling edge preceding the
falling edge of CS* and DS*. The rising edge of R/W* occurs after the rising
edge of CS* and DS*. Data is latched on the address-data bus on the rising edge
of WR* or DS*.
3.8.1.2 Separated
Address/Data Bus
The timing for a read or write cycle using the separated address and data buses is
essentially the same as over the multiplexed bus. The one exception is that the
address must be driven onto the ADDR[6:0] bus rather than the AD[7:0] bus.
N8954DSC
Conexant
3-21
Bt8954
3.0 Circuit Descriptions
3.8 Microcomputer Interface
Voice Pair Gain Framer
3.8.2 Interrupt Request
The open drain interrupt request output (IRQ*) indicates when a particular set of
transmit, receive, or common status registers has been updated. Eight maskable
interrupt sources are requested on the common IRQ* pin:
TX = Transmit 6 ms Frame
TX_ERR = Transmit Channel Errors or Transmit HDSL Frame
Repositioned
3. RX = Receive 6 ms Frame
4. RX_ERR = Receive Channel Errors or Framer State Transition to
IN_SYNC
5. PLL_ERR = PLL Error
6. LD_TSIG = Load Transmit Signaling Interrupt
7. RD_RSIG = Read Receive Signaling Interrupt
8. SIG_FIFO_ERR = Signaling FIFO Error Interrupt
All interrupt events are edge-sensitive. Tx and Rx interrupts are synchronized
to the DSL channel’s 6 ms frame. The LD_TSIG, RD_RSIG, and
SIG_FIFO_ERR occur every 1 ms, 2 ms, 3, ms, or 6 ms. The rate is dependent on
the value of EXTRA_SIG_UPDATE in CMD_1. TX_ERR, RX_ERR, and
PLL_ERR occur whenever these errors are detected.
The basic structure of each interrupt source is illustrated in Figure 3-22 and
has two associated registers: Interrupt Mask register [IMR; 0xD1], and Interrupt
Status register [ISR; 0xD0]. A 0 in a given bit of the IMR enables the
corresponding interrupt. A 1 in a given bit of the IMR disables the corresponding
interrupt, thereby preventing it from activating IRQ*. By reading the ISR, the MC
can determine the cause of an interrupt event. Active interrupts are indicated by
ISR bits that are read high while inactive interrupts are indicated by ISR bits that
are read low. Writing a 0 to an Interrupt Status register bit [ISR; 0xD0] clears the
corresponding interrupt, and if no other interrupts are pending, deactivates IRQ*.
Writing a 1 to any ISR bit has no effect. IRQ* is an open-drain output and must be
tied to a pullup resistor. This allows IRQ* to be tied together with a common
interrupt request.
1.
2.
Figure 3-22. Interrupt Logic
Read IMR
Mask
Data
IRQ*
Write IMR
Read ISR
Interrupt
Event
Set
Status
Other Interrupt
Sources
Reset
Write ISR
3-22
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.8 Microcomputer Interface
Voice Pair Gain Framer
3.8.3 Reset
The reset input (RST*) is an active-low input that presets all IMR bits and clears
all interrupt enables (disabling the IRQ* output). The following registers are reset
synchronously by the GCLK to a value of 0x00: ISR, RCMD_1, RCMD_2,
DFRAME_LEN, SYNC_WORD, CMD_1, PFRAME_LEN, and
PCM_FORMAT. This means the fPLL must be programmed, and then a reset must
be applied to the RST* pin. When a reset is applied to the RST* pin, the IMR is
asynchronously set to a value of 0xFF.
The following configuration of the Bt8954 is not valid:
NUM_SBITS [TCMD2] = 0
EXTRA_Z_BIT [CMD_1] = 1
NUM_CHAN [PCM_FORMAT1] = 0x0B
DFRAME_LEN = 0x58
N8954DSC
Conexant
3-23
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
3.9 PLL
The bit pump is the clock master of Bt8954, which in turn is a clock master of the
codecs. The PLL synthesizes a variety of (ADPCMCK, PCMCKO) frequency
pairs from HCLK (HCLK is 32 times the bit clock, BCLK). Figure 3-23 details
the PLL architecture. First, HCLK is scaled by 1/PLL_X in the prescaler to
produce fREF . The PLL output frequency, fPLL, is in general a non-integer
multiple (PLL_INT.FRACP) of fREF . The fPLL is post-scaled by 1/PLL_W to
give ADPCMCK, which in turn is scaled by 1/PLL_Y to give PCMCKO. The
frequency of GCLK, fGCLK, is fPLL divided by P_FACTOR. GCLK clocks all the
registers in the microcomputer interface.
P_FACTOR is given by the PLL_P[1:0] bits of the PLL_SCALE register
[0xB5.6:5]. When PLL_P[1] = 1 and PLL_P[0] = 1, then the P_FACTOR is set to
8. When PLL_P[1] = 1 and PLL_P[0] = 0, then the P_FACTOR is set to 4. When
PLL_P[1] = 0, then the P_FACTOR is dependent on the value of PLL_W. This
allows you to adjust the value of GCLK. A lower value of GCLK lowers the
power requirements of the device and the maximum speed of the microprocessor
bus. The value for fPLL is either 196.608 MHz or 204.800 MHz.
Figure 3-23. Functional Diagram of the PLL
OUT_OF_LOCK
HCLK
FREF = fH/PLL_X
fH
1/PLL_X
PLL
CORE
fPLL=PLL_INT.FRACP x fREF
1/PLL_INT.FRACP
1/P_FACTOR
1/PLL_W
ADPCMCK
1/PLL_Y
PCMCKO
GCLK
NOTE(S): Legend—fH = HCLK frequency; fP = PCMCKO frequency; fG = GCLK frequency; fA = ADPCMCK frequency.
3-24
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
ADPCMCK and PCMCKO are related to BCLK and HCLK through the
following equations:
f B = N x 64kbps + Non – PayloadBitRate
f H = 32 x f B
fH
f REF = -----------------PLL_X
f PLL = f REF x PLL_INT.FRACP
f PLL
f ADPCMCK = -------------------PLL_W
f ADPCMCK
f PCMCKO = -------------------------PLL_Y
The fractional part, FRACP, is scaled as follows:
A
 ( FRAC ) + ---
B

FRACP = -------------------------------
 65536 


The OUT_OF_LOCK output is the PLL_ERR interrupt. PLL_INT[5:0] bits
are in the PLL_INT register [0xB0], FRAC bits are in the PLL_FRAC_HI and
PLL_FRAC_LO registers [0xB1 and 0xB2], the A Bit is in the PLL_A register
[0xB3], and the B bit is in the PLL_B register [0xB4]. PLL_X is represented by
the PLL_X register bits of the PLL_SCALE register [0xB5.0,1], as given in
Table 3-5.
Table 3-5. PLL_X Register Mapping
N8954DSC
PLL_X[1]
PLL_X[0]
fH/fREF
0
0
1
0
1
2
1
1
4
1
0
Sleep Mode
Conexant
3-25
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
PLL_W and PLL_Y are represented by the PLL_C[2:0] register bits of the
PLL_SCALE register [0xB5.4:2], as given in Table 3-6. PLL_P bits are also
selected in the PLL_SCALE register to control the internal GCLK frequency, as
detailed in Table 3-7.
Table 3-6. PLL_C Register Bit Representation of PLL_W and PLL_Y
fPLL
PLL_C[2]
PLL_C[1]
PLL_C[0]
PLL_W
fADPCMCK
PLL_Y
fPCMCKO
204.800 MHz
0
0
0
10
20.480 MHz
10
2.048 MHz
196.608 MHz
0
0
0
1
1
0
24
8.192 MHz
4
2.048 MHz
Table 3-7. PLL_P Register Bit Representation of P_FACTOR
PLL_P[1]
PLL_P[0]
PLL_W
P_FACTOR
fGCLK = fPLL / P_FACTOR
Max µP Freq = fGCLK/2
0
0
0
0
0
0
10
24
32
5
6
4
fPLL / 5
fPLL / 6
fPLL / 4
fPLL / 10
fPLL / 12
fPLL / 8
0
0
0
1
1
1
10
24
32
10
12
8
fPLL / 10
fPLL / 12
fPLL / 8
fPLL / 20
fPLL / 24
fPLL / 16
1
0
X
4
fPLL / 4
fPLL / 8
1
1
X
8
fPLL / 8
fPLL / 16
3-26
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
Ideally, the Voltage Crystal Oscillator (VCO) should be operated around
200 MHz. Therefore, fGCLK is approximately 50 MHz. Table 3-8 lists the various
factors that synthesize different frequencies for fPLL = 196.608 MHz. Not all
possible configurations are illustrated.
Table 3-9 lists the various factors that synthesize different frequencies for
fPLL = 204.800 MHz.
Table 3-8. Factors for fPLL = 196.608 MHz (1 of 2)
N
N x 64
(kbps)
Non-Payload
Bit Rate (kHz)
fB (kHz)
fH (MHz)
fH/fREF
fREF (MHz)
INT
FRAC
A/B
2
128
8
136
4.352
1
4.352
45
11565
3/17
16
144
4.608
1
4.608
42
43690
2/3
32
160
5.120
1
5.120
38
26214
2/5
40
168
5.376
1
5.376
36
37449
1/7
64
192
6.144
1
6.144
32
0
0/1
72
200
6.400
1
6.400
30
47185
23/25
8
264
8.448
1
8.448
23
17873
5/11
16
272
8.704
1
8.704
22
38550
10/17
32
288
9.216
1
9.216
21
21845
1/3
40
296
9.472
1
9.472
20
49594
30/37
64
320
10.240
1
10.240
19
13107
1/5
72
328
10.496
1
10.496
18
47953
7/41
8
392
12.544
1
12.544
15
44136
24/49
16
400
12.800
1
12.800
15
23592
24/25
32
416
13.312
1
13.312
14
50412
4/13
40
424
13.568
1
13.568
14
32149
39/53
64
448
14.336
1
14.336
13
46811
3/7
72
456
14.592
1
14.592
13
31043
7/19
8
520
16.640
1
16.640
11
53437
3/65
16
528
16.896
1
16.896
11
41704
8/11
32
544
17.408
1
17.408
11
19275
5/17
40
552
17.664
1
17.664
11
8548
4/23
64
576
18.432
1
18.432
10
43690
2/3
72
584
18.688
1
18.688
10
34114
46/73
4
6
8
256
384
512
N8954DSC
Conexant
3-27
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
Table 3-8. Factors for fPLL = 196.608 MHz (2 of 2)
N
N x 64
(kbps)
Non-Payload
Bit Rate (kHz)
fB (kHz)
fH (MHz)
fH/fREF
fREF (MHz)
INT
FRAC
A/B
12
768
8
776
24.832
2
12.416
15
54725
91/97
16
784
25.088
2
12.544
15
44136
24/49
32
800
25.600
2
12.800
15
23592
24/25
40
808
25.856
2
12.928
15
13626
30/101
64
832
26.624
2
13.312
14
50412
4/13
72
840
26.880
2
13.440
14
41194
2/35
8
1160
37.120
4
9.280
21
12203
37/145
16
1168
37.376
4
9.344
21
2693
19/73
32
1184
37.888
4
9.472
20
49594
30/37
40
1192
38.144
4
9.536
20
40465
27/149
64
1216
38.912
4
9.728
20
13797
1/19
72
1224
39.168
4
9.792
20
5140
4/51
18
1152
Table 3-9. Factors for fPLL = 204.800 MHz (1 of 2)
N
N x 64
(kbps)
Non-Payload
Bit Rate (kHz)
fB (kHz)
fH (MHz)
fH/fREF
fREF (MHz)
INT
FRAC
A/B
2
128
8
136
4.352
1
4.352
47
3855
1/17
16
144
4.608
1
4.608
44
29127
1/9
32
160
5.120
1
5.120
40
0
0/1
40
168
5.376
1
5.376
38
6241
11/21
64
192
6.144
1
6.144
33
21845
1/3
72
200
6.400
1
6.400
32
0
0/1
8
264
8.448
1
8.448
24
15887
17/33
16
272
8.704
1
8.704
23
34695
9/17
32
288
9.216
1
9.216
22
14563
5/9
40
296
9.472
1
9.472
21
40738
22/37
64
320
10.240
1
10.240
20
0
0/1
72
328
10.496
1
10.496
19
33567
9/41
4
3-28
256
Conexant
N8954DSC
Bt8954
3.0 Circuit Descriptions
3.9 PLL
Voice Pair Gain Framer
Table 3-9. Factors for fPLL = 204.800 MHz (2 of 2)
N
N x 64
(kbps)
Non-Payload
Bit Rate (kHz)
fB (kHz)
fH (MHz)
fH/fREF
fREF (MHz)
INT
FRAC
A/B
6
384
8
392
12.544
1
12.544
16
21399
25/49
16
400
12.800
1
12.800
16
0
0/1
32
416
13.312
1
13.312
15
25206
2/13
40
424
13.568
1
13.568
15
6182
34/53
64
448
14.336
1
14.336
14
18724
4/7
72
456
14.592
1
14.592
14
2299
29/57
8
520
16.640
1
16.640
12
20164
60/65
16
528
16.896
1
16.896
12
7943
25/33
32
544
17.408
1
17.408
11
50115
13/17
40
552
17.664
1
17.664
11
38941
47/69
64
576
18.432
1
18.432
11
7281
7/9
72
584
18.688
1
18.688
10
62842
54/73
8
776
24.832
2
12.416
16
32430
18/97
16
784
25.088
2
12.544
16
21399
25/49
32
800
25.600
2
12.800
16
0
0/1
40
808
25.856
2
12.928
15
55154
6/101
64
832
26.624
2
13.312
15
25206
2/13
72
840
26.880
2
13.440
15
15603
17/21
8
1160
37.120
4
9.280
22
4519
21/29
16
1168
37.376
4
9.344
21
60149
35/73
32
1184
37.888
4
9.472
21
40738
22/37
40
1192
38.144
4
9.536
21
31228
84/149
64
1216
38.912
4
9.728
21
3449
5/19
72
1224
39.168
4
9.792
20
59967
89/153
8
12
18
512
768
1152
N8954DSC
Conexant
3-29
Bt8954
3.0 Circuit Descriptions
3.9 PLL
3-30
Voice Pair Gain Framer
Conexant
N8954DSC
4
4.0 Registers
For registers that contain less than 8 bits, assigned bits reside in LSB positions, unassigned bits are ignored
during write cycles, and are indeterminate during read cycles. The LSB in all registers is bit position 0.
All registers are randomly accessible. All register values written can be read back except where noted.
4.1 Register Types
The MC must read and write real-time registers (receive and transmit EOC, IND, S-bit, and status registers),
within a prescribed time interval (1–6 ms) after the DSL channel’s 6 ms frame interrupt to avoid reading or
writing transitory data values. Failure to read real-time registers within the prescribed interval results in a loss of
data.
The MC writes to non-real-time command registers are event-driven and occur when the system initializes,
changes modes, or responds to an error condition.
The MC reads can be interrupt-event driven, polled, or a combination of both, allowing the choice to be
dictated by system architecture. Polled procedures can avoid reading transitory real-time data by monitoring the
Interrupt Status register bits [ISR; 0xD0] to determine when a particular group of registers has been updated.
Interrupt-driven and polled procedures must complete reading within the prescribed 1–6 ms interval following
DSL frame interrupts.
4.2 Register Groups
Bt8954 command, status, and real-time registers are divided into three groups:
• Transmit
• Receive
• Common
The group of Transmit and Receive registers only affects operation or reports status of the DSL channel.
Transmit registers reference data flow from the PCM channel to the DSL channel output. Receive registers
reference data flow from the DSL channel to the PCM channel outputs. Common registers affect overall
operation, primarily the PCM channel and the PLL.
N8954DSC
Conexant
4-1
Bt8954
4.0 Registers
4.3 Address Map
Voice Pair Gain Framer
4.3 Address Map
Table 4-1 provides the address map.
Table 4-1. Address Map (1 of 2)
4-2
Address
(Hex)
Acronym
0x80
TEOC_LO
Transmit Embedded Operations Channel Low
0x81
TEOC_HI
Transmit Embedded Operations Channel High
0x82
TIND_LO
Transmit Indicator Bits Low
0x83
TIND_HI
Transmit Indicators Bits High
0x84
TSFIFO_I, TSFIFO_O
Transmit Signaling FIFOs
0x85
TFIFO_WL
Transmit FIFO Water Level
0x86
TCMD_1
Transmit Command Register 1
0x87
TCMD_2
Transmit Command Register 2
0x90
RCMD_1
Receive Command Register 1
0x91
RCMD_2
Receive Command Register 2
0xA0
DFRAME_LEN
DSL Frame Length
0xA1
SYNC_WORD
Sync Word
0xA2
RFIFO_WL_LO
Rx FIFO Water Level Low
0xA3
RFIFO_WL_HI
Rx FIFO Water Level High
0xB0
PLL_INT
0xB1
PLL_FRAC_HI
PLL_FRAC_HI
0xB2
PLL_FRAC_LO
PLL_FRAC_LO
0xB3
PLL_A
PLL_A
0xB4
PLL_B
PLL_B
0xB5
PLL_SCALE
0xC0
CMD_1
Command Register 1
0xC1
REV_ID
Revision Identification
0xD0
ISR
Interrupt Status Register
0xD1
IMR
Interrupt Mask Register
0xD3
SCR_RST
Scrambler Reset
0xD4
TFIFO_RST
Transmit FIFO Reset
0xD5
TSFIFO_PTR_RST
Reset Pointer to Transmit Signaling FIFOs
0xD6
RSFIFO_PTR_RST
Reset Pointer to Receive Signaling FIFOs
Description
PLL_INT
PLL_SCALE
Conexant
N8954DSC
Bt8954
4.0 Registers
4.3 Address Map
Voice Pair Gain Framer
Table 4-1. Address Map (2 of 2)
Address
(Hex)
Acronym
0xD7
RFIFO_RST
Receive Elastic Store FIFO Reset
0xD8
SYNC_RST
Receive Framer Synchronization Reset
0xD9
ERR_RST
Error Count Reset
0xDA
RX_RST
Reset Receiver
0xDB
UPDATE_TSFIFO_0
Update TSFIFO_0
0xDC
UPDATE_RSFIFO_0
Update RSFIFO_0
0xE0
REOC_LO
Receive Embedded Operations Channel Low
0xE1
REOC_HI
Receive Embedded Operations Channel High
0xE2
RIND_LO
Receive Indicator Bits Low
0xE3
RIND_HI
Receive Indicator Bits High
0xE4
RSFIFO_I, RSFIFO_O
0xE5
RSTATUS_1
Receive Status 1
0xE6
RSTATUS_2
Receive Status 2
0xE7
TSTATUS_1
Transmit Status 1
0xE8
CRC_CNT
CRC Error Count
0xE9
FEBE_CNT
Far End Block Error Count
0xF0
FRAME_LEN
0xF1
PCM_FORMAT
N8954DSC
Description
Receive Signaling FIFOs
PCM Frame Length
PCM Format
Conexant
4-3
Bt8954
4.0 Registers
4.4 Transmitter Registers
Voice Pair Gain Framer
4.4 Transmitter Registers
Transmitter registers are summarized in Table 4-2.
Table 4-2. Transmitter Register Summary
Address
Register Label
Bits
Name/Description
0x80
TEOC_LO
8
Transmit Embedded Operations Channel
0x81
TEOC_HI
5
Transmit Embedded Operations Channel
0x82
TIND_LO
8
Transmit Indicator
0x83
TIND_HI
5
Transmit Indicator
0x84
TSFIFO_I, TSFIFO_O
48 x 8
0x85
TFIFO_WL
8
TFIFO Water Level
0x86
TCMD_1
6
Transmit Command Register 1
0x87
TCMD_2
8
Transmit Command Register 2
Transmit Signaling FIFOs
0x80, 0x81—Transmit Embedded Operations Channel (TEOC_LO, TEOC_HI)
The Transmit Embedded Operations Channel (EOC) holds 13 EOC bits for transmission in the next frame.
Refer to Table 3-1 on page 3-3 for the EOC bit positions within the frame. The Payload Mux samples TEOC
coincident with the DSL channel’s transmit 6 ms frame interrupt. Unmodified registers repeatedly output their
contents in each frame. The most significant bit, TEOC[12], is transmitted first.
TEOC_LO (Address 0x80)
7
6
5
4
3
2
1
0
11
10
9
8
TEOC[7:0]
TEOC_HI (Address 0x81)
15
14
13
—
—
—
12
TEOC[12:8]
0x82, 0x83—Transmit Indicator Bits (TIND_LO, TIND_HI)
Transmit Indicator (IND) holds 13 IND bits for transmission in the next frame and includes the FEBE bit,
TIND[1]. Refer to Table 3-1 on page 3-3 for the IND bit positions within the frame. The Payload Mux samples
TIND coincident with the DSL channel’s transmit 6 ms frame interrupt. Unmodified registers repeatedly output
their contents in each frame. The most significant bit, TIND[12], is transmitted first.
NOTE:
4-4
Bt8954 does not automatically output FEBE. Proper transmit of FEBE requires the
MC to copy the CRC_ERR bit from RSTATUS_2 [0xE6] to TIND[1].
Conexant
N8954DSC
Bt8954
4.0 Registers
4.4 Transmitter Registers
Voice Pair Gain Framer
TIND_LO (Address 0x82)
7
6
5
4
3
2
1
0
11
10
9
8
TIND[7:0]
TIND_HI (Address 0x83)
15
14
13
—
—
—
12
TIND[12:8]
0x84—Transmit Signaling FIFOs (TSFIFO_I, TSFIFO_O)
TSFIFO_I[48:1],
TSFIFO_O[48:1]
Employing a double-buffering scheme, two 48-byte FIFOs (transmit signaling input FIFO
[TSFIFO_I] and transmit signaling output FIFO [TSFIFO_0]), transmit signaling information,
as illustrated in Figure 4-1.
Figure 4-1. Transmit Signaling FIFOs
TSFIFO_I[48]
From MC
TSFIFO_O[48]
•
•
•
•
•
•
TEST_TSFIFO
I
O
TSFIFO_I[2]
TSFIFO_O[2]
TSFIFO_I[1]
TSFIFO_O[1]
UPDATE_TSFIFO_O(1)
To
Transmitter
To MC(1)
LD_TSIG
(From Transmitter)
NOTE(S):
(1)
From MC; for testing only
N8954DSC
Conexant
4-5
Bt8954
4.0 Registers
4.4 Transmitter Registers
Voice Pair Gain Framer
The number of signaling bits is set in TCMD_2 address [0x87]. The MSB of the signaling
bits is always in the MSB of the TSFIFO. An example of three signaling bits is illustrated in
Figure 4-2.
Up to 48 bytes of transmit signaling information can be loaded into TSFIFO_I by the MC
after it receives the Load Transmit Signaling Interrupt (LD_TSIG) from the transmitter. The
MC has 6 ms, 3 ms, 2 ms, or 1 ms, (depending on the EXTRA_SIG_UPDATE configuration in
the CMD_1 register [0xC0.4:3] from the current LD_TSIG to the next LD_TSIG to load 48,
24, 16, or 8 TSFIFO_I entries. TSFIFO_I is loaded into TSFIFO_O at every LD_TSIG
interrupt before TSFIFO_I is modified by the MC.
MC access to TSFIFO_I is provided by first writing to TSFIFO_PTR_RST [0xD5] to reset
the write pointer, and then writing up to 48 entries sequentially. TSFIFO_I[1] is written first.
Bt8954 increments the TSFIFO_I write pointer after each write cycle to the TSFIFOs address.
The pointer wraps around to point to the first entry (TSFIFO_I[1]) after the 48th entry
(TSFIFO_I[48]) has been written. Therefore, the TSFIFO_I write pointer needs to be reset
only once (that is, during initialization) if 48 entries are written every 6 ms.
For testing purposes, MC read access to TSFIFO_O is provided by first writing to
TSFIFO_PTR_RST [0xD5] to reset the TSFIFO_O read pointer, and then reading up to 48
entries sequentially. TSFIFO_O[1] is read first. Bt8954 increments the TSFIFO_O read
pointer after each read access to the TSFIFOs address. The pointer wraps around to point to
the first entry (TSFIFO_O[1]) after the 48th entry (TSFIFO_O[48]) has been read.
Also, for testing, writing any value to the UPDATE_TSFIFO_O address [0xDB] initiates
copying TSFIFO_I into TSFIFO_O, provided the TEST_TSFIFO bit in TCMD_1 [0x86] is
set.
Figure 4-2. Example of Three Signaling Bits
RSFIFO
TSFIFO
MSB
LSB
MSB
1 2 3 X X X X X
LSB
X X X X X 1 2 3
0x85—Transmit FIFO Water Level (TFIFO_WL)
Transmit FIFO Water Level contains the number of BCLK cycles to delay from the PCM 6 ms frame to the start
of the DSL transmit SYNC word. A value of zero equals 1 BCLK delay.
7
6
5
4
3
2
1
0
TFIFO_WL[7:0]
4-6
Conexant
N8954DSC
Bt8954
4.0 Registers
4.4 Transmitter Registers
Voice Pair Gain Framer
0x86—Transmit Command Register 1 (TCMD_1)
Real-time commands (bits 0–5) are sampled by the OH multiplexer on the respective transmit frame to affect
operation in the next outgoing frame. DOH_EN and FORCE_ONE command bit combinations provide the
transmit data encoding options needed to perform standard DSL channel start-up procedures.
7
6
5
4
3
2
1
0
—
—
—
TEST_TSFIFO
FORCE_ONE
DOH_EN
ICRC_ERR
SCRAM_EN
TEST_TSFIFO
Test Transmit Signaling FIFO—Enables the copying of TSFIFO_I into TSFIFO_O by the MC,
so that the TSFIFOs can be tested from the MC.
0 = Disable testing of TSFIFOs; enable normal operation
1 = Enable testing of TSFIFOs; disable normal operation
FORCE_ONE
Force All 1s Payload—Transmit payload data bytes are replaced by all 1s. FORCE_ONE and
SCRAM-EN are set, and DOH_EN is cleared to enable output of a 4-level framed scrambled
1s signal.
0 = Normal payload transmission
1 = Force 4-level 1s payload
DOH_EN
DSL Overhead Enable—The OH multiplexer inserts EOC, IND, and CRC bits. Otherwise,
transmit overhead bits, except SYNC WORD, are forced to 4-level 1s.
0 = OH transmitted as 4-level 1s
1 = Normal OH transmission
ICRC_ERR
Inject CRC Error—Logically inverts the 6 calculated CRC bits in the next frame.
0 = Normal CRC transmission
1 = Transmit errored CRC
SCRAM_EN
Scrambler Enable—All transmit DSL channel bits, except SYNC WORD bits, are scrambled
per the SCR_TAP setting in TCMD_2 [0x87]. Otherwise, transmit data passes through the
scrambler unchanged.
0 = Scrambler bypassed
1 = Scrambler enabled
N8954DSC
Conexant
4-7
Bt8954
4.0 Registers
4.4 Transmitter Registers
Voice Pair Gain Framer
0x87—Transmit Command Register 2 (TCMD_2)
7
6
EN_AUTO_
TFIFO_RST
REPEAT_EN
EN_AUTO_TFIFO
_RST
5
4
3
2
NUM_SBITS[3:0]
1
0
SCRAM_TAP
DD_LOOP
Enable Automatic TFIFO_RST—When set, the TFIFO is reset the instant that the Receive
Framer changes state from SYNC_ACQUIRED to IN_SYNC.
0 = TFIFO not automatically reset by SYNC_ACQUIRED → IN_SYNC
1 = TFIFO automatically reset by SYNC_ACQUIRED → IN_SYNC
REPEAT_EN
Enable Repeater Mode—When set, DSL frames received on RDAT are re-transmitted with
new overhead after bypassing all the FIFOs.
0 = Normal transmit
1 = Repeater mode
NUM_SBITS[3:0]
Number of valid S-Bits in each TSFIFO and RSFIFO register—
0 = No S-bits transmitted or received
1 → 8 = 1 → 8 valid S-bits in each TSFIFO and RSFIFO register
SCRAM_TAP
Scrambler Tap—Selects which delay stage, 5th or 18th, to tap for feedback in the transmit
scrambler. The system’s DSL terminal type dictates which scrambler tap should be selected.
0 = HTU-C or LTU terminal type, scrambler taps 5th delay stage
1 = HTU-R or NTU terminal type, scrambler taps 18th delay stage
For the repeater (Figure 2):
0 = Bt8954 (C → R), scrambler tapes 5th delay stage
1 = Bt8954 (R → C), scrambler tapes 18th delay stage
DD_LOOP
Loopback to DSL on the DSL Side—Receive DSL data (RDAT) is switched to transmit DSL
data (TDAT) to accomplish a loopback of the DSL channel on the DSL side. Loopback data is
switched at I/O pins and does not alter DSL receive operations. If the DSCRAM_EN
[RCMD_2; 0x91.5] and SCAM_EN [TCMD_1; 0x86.0] bits are set, RDAT is switched to
TDAT after descrambling and scrambling.
0 = Normal transmit
1 = TDAT supplied by RDAT pin
4-8
Conexant
N8954DSC
Bt8954
4.0 Registers
4.5 Receiver Registers
Voice Pair Gain Framer
4.5 Receiver Registers
One group of registers configures the receiver and controls the mapping of DSL payload bytes into the receiver
elastic store (RFIFO). The configuration register defines the DSL receive framer’s criteria for loss and recovery
of frame alignment by selecting the number of detected SYNC WORD errors used to declare loss of sync or
needed to acquire sync. Refer to Figure 3-4, Receive Framer Finite State Machine on page 3-6 The DSL write
registers are listed in Table 4-3. Frame alignment criteria are programmable to meet different standard
application requirements.
Table 4-3. DSL Receive Write Registers
Address
Register Label
Bits
Name/Description
0x90
RCMD_1
8
Configuration
0x91
RCMD_2
8
Configuration
0x90—Receive Command Register 1 (RCMD_1)
7
6
EN_AUTO_
RFIFO_RST
FRAMER_EN
EN_AUTO_RFIFO
_RST
5
4
3
LOSS_SYNC[2:0]
2
1
0
REACH_SYNC[2:0]
Enable Automatic RFIFO_RST-—When set, the RFIFO is reset at the instant that the receive
framer changes state from the SYNC_ACQUIRED to the IN_SYNC state.
0 = RFIFO not automatically reset by SYNC_ACQUIRED → IN_SYNC
1 = RFIFO automatically reset by SYNC_ACQUIRED → IN_SYNC
FRAMER_EN
Receive Framer Enable—Instructs the receive framer to search for the SYNC WORD pattern
programmed in SYNC_WORD [0xA1]. When disabled, the framer does not count errors or
generate interrupts.
FRAMER_EN
0
1
N8954DSC
Receive Framer Search
Disabled; framer forced to OUT_OF_SYNC
Enabled; search for SYNC_WORD
Conexant
4-9
Bt8954
4.0 Registers
4.5 Receiver Registers
Voice Pair Gain Framer
Loss of Sync Framing Criteria—Contains the number of consecutive DSL frames in which the
SYNC word is not detected before the receive framer moves from the IN_SYNC to the
OUT_OF_SYNC state. LOSS_SYNC determines the number of SYNC_ERRORED
intermediate states the framer must pass through during loss of frame sync. ETSI standard
criteria require six consecutive frames without SYNC word detected.
LOSS_SYNC[2:0]
LOSS_SYNC
000
001
010
011
100
101
110
111
REACH_SYNC[2:0]
OUT_OF_SYNC Criteria
1 frame not containing SYNC
2 consecutive frames
3 consecutive frames
4 consecutive frames
5 consecutive frames
6 consecutive frames
7 consecutive frames
8 consecutive frames
Reach Sync Framing Criteria—Contain the number of consecutive DSL frames in which the
SYNC WORD is detected before the receive framer moves from the OUT_OF_SYNC to the
IN_SYNC state. REACH_SYNC determines the number of SYNC_ACQUIRED intermediate
states the framer must pass through during recovery of frame sync. ETSI standard criteria
require two consecutive frames containing SYNC.
REACH_SYNC
000
001
010
011
100
101
110
111
IN_SYNC Criteria
1 frame containing SYNC
2 consecutive frames
3 consecutive frames
4 consecutive frames
5 consecutive frames
6 consecutive frames
7 consecutive frames
8 consecutive frames
0x91—Receive Command Register 2 (RCMD_2)
7
6
5
4
TEST_RSFIFO
PD_LOOP
DSCRAM_EN
DSCRAM_TAP
TEST_RSFIFO
3
2
1
0
THRESH_CORR[3:0]
Test Receive Signaling FIFO—Enables the copying of RSFIFO_I into RSFIFO_O, and write
access to RSFIFO_I by the MC. Setting this bit enables the testing of the RSFIFOs from the
MC.
0 = Disabled testing of RSFIFOs; enabled normal operation
1 = Enabled testing of RSFIFOs; disabled normal operation
PD_LOOP
Loopback to PCM on DSL Side—Transmit DSL data (TDAT) is connected back toward the
PCM interface to accomplish a loopback of the PCM channel on the DSL side. Receive DSL
data (RDAT) is ignored, but DSL transmit continues without interruption. PD_LOOP requires
the descrambler and scrambler to use the same tap, as opposed to their normal opposing tap
selection.
0 = Normal receive
1 = RDAT supplied by TDAT
4-10
Conexant
N8954DSC
Bt8954
4.0 Registers
4.5 Receiver Registers
Voice Pair Gain Framer
DSCRAM_EN
Descrambler Enable—When enabled, all receive DSL channel data, except SYNC WORD bits,
are descrambled per the DSCRAM_TAP setting. Otherwise the data passes through the
descrambler unchanged.
0 = Descrambler bypassed
1 = Descrambler enabled
DSCRAM_TAP
Descrambler Tap—Selects which delay stage, 5th or 18th, to tap for feedback in the
descrambler. The system’s terminal type dictates which tap should be selected.
0 = HTU-C or LTU terminal type, descrambler selects tap 18
1 = HTU-R or NTU terminal type, descrambler selects tap 5
For the repeater (Figure 2):
0 = Bt8954 (R → C), scrambler taps 5th delay stage
1 = Bt8954 (C → R), scrambler taps 18th delay stage
THRESH_CORR[3:0] SYNC
Threshold Correlation—Upon the receive framer’s entry to a SYNC_ERRORED state,
the number of SYNC WORD locations searched is determined by the result of previous states’
threshold correlation. During an IN_SYNC state, the framer searches the two most probable
SYNC word locations at 6 ms ± 1 quat, corresponding to 0 or 4 STUFF bits. One of the two
locations searched must correctly match the entire 14-bit SYNC word or else the framer enters
a SYNC_ERRORED state.
The highest number of matching bits found among the search locations is compared to the
selected THRESH_CORR value to determine if the framer should expand the number of
search locations. If the highest number of matching bits meets or exceeds the threshold, but
wasn’t a complete match, the framer progresses to the next SYNC_ERRORED state and
continues to each of the two most probable locations. Otherwise, the framer progresses to the
next SYNC_ERRORED state, increments the number of locations to be searched, and
examines quats on either side of the prior search locations. For example, if the location with
highest number of matching bits is below the threshold during IN_SYNC, then the framer
enters the first SYNC_ERRORED state and searches from the prior location at 6 ms ± 2 quats,
and at 6 ms exactly. The effect of Threshold Correlation on the number of search locations is
depicted in Figure 3-5 on page 3-7.
THRESH_CORR
1010
1011
1100
1101
1110
N8954DSC
Conexant
SYNC Threshold Correlation
10 or more out of 14 bits
11 or more out of 14 bits
12 or more out of 14 bits
13 or more out of 14 bits
14 out of 14 bits
4-11
Bt8954
4.0 Registers
4.6 DSL Channel Configuration
Voice Pair Gain Framer
4.6 DSL Channel Configuration
The DSL Channel Configuration Write registers are listed in Table 4-4.
Table 4-4. DSL Channel Configuration Write Register
Address
Register Label
Bits
Name/Description
0xA0
DFRAME_LEN
8
DSL Frame Length
0xA1
SYNC_WORD
7
SYNC Word (sign only)
0xA2
RFIFO_WL_LO
8
RX FIFO Water Level
0xA3
RFIFO_WL_HI
1
RX FIFO Water Level
0xA0—DSL Frame Length (DFRAME_LEN)
7
6
5
4
3
2
1
0
DFRAME_LEN[7:0]
DFRAME_LEN[7:0]
DSL Frame Length—Contains the number of BCLK bits (less 1), in the range of 8 to 152, that
are transmitted and received in a DSL payload block. Each payload block consists of an integer
number of 8-bit bytes (1 byte per voice channel) plus a variable number of S-bits (0–8) plus 0
or 1 EXTRA_Z_BIT. Therefore, DFRAME_LEN = #Voice Channels x 8 + #S-bits, –1 if
EXTRA_Z_BIT (CMD_1; addr 0xC0) = 0 but DFRAME_LEN = Voice Channels x 8 + SBITS
if EXTRA_Z_BIT = 1.
0xA1—Sync Word (SYNC_WORD)
7
—
SYNC_WORD[6:0]
6
5
4
3
2
1
0
SYNC_WORD[6:0]
SYNC_WORD—Holds the 7 sign bits ± of the 7-quat (14-bit) transmit and receive SYNC
word. Transmit SYNC word magnitude bits are forced to 0. SYNC_WORD[0] is the sign bit of
the first transmit quat. Sign precedes magnitude on the transmit data (TDAT) output. The
receive framer searches DSL data (RDAT) for patterns matching SYNC_WORD.
0 = Negative sign bit
1 = Positive sign bit
4-12
Conexant
N8954DSC
Bt8954
4.0 Registers
4.6 DSL Channel Configuration
Voice Pair Gain Framer
0xA2, 0xA3—Rx FIFO Water Level (RFIFO_WL_LO, RFIFO_WL_HI)
Receive FIFO Water Level sets the BCLK bit delay from the master DSL channel’s receive 6 ms frame to the
PCM receive 6 ms frame. The delay is programmed in BCLK bit intervals, in the range of 1 to 1024 bits.
A value of 0 equals 1 BCLK bit delay.
RFIFO_WL_LO
(Address 0xA2)
7
6
5
4
3
2
1
0
RFIFO_WL[7:0]
RFIFO_WL_HI
(Address 0xA3)
15
14
13
12
11
10
9
8
—
—
—
—
—
—
RFIFO_WL[9]
RFIFO_WL[8]
N8954DSC
Conexant
4-13
Bt8954
4.0 Registers
4.7 PLL Configuration
Voice Pair Gain Framer
4.7 PLL Configuration
The PLL synthesizes the PCM clock output (PCMCKO) and the ADPCM clock (ADPCMCK) from the DSL
HCLK (HCLK = 32 x BCLK). Refer to Tables 3-5 through 3-9 on pages 3-25 through 3-28 for the register
values to load into these registers for different BCLK, PCMCLK, and ADPCMCK frequencies. A list of PLL
configuration write registers is displayed in Table 4-5.
Table 4-5. PLL Configuration Write Registers
Address
Register Label
Bits
Name/Description
0xB0
PLL_INT
6
PLL_INT Register
0xB1
PLL_FRAC_HI
8
MSB of PLL_FRAC
0xB2
PLL_FRAC_LO
8
LSB of PLL_FRAC
0xB3
PLL_A
8
PLL_A Register
0xB4
PLL_B
8
PLL_B Register
0xB5
PLL_SCALE
7
PLL_X and PLL_C for Pre-Scaling and Post-Scaling
0xB0—PLL_INT Register (PLL_INT)
The PLL_INT register contains the integer part of the fPLL/fREF ratio.
7
6
—
—
5
4
3
2
1
0
PLL_INT[5:0]
0xB1—PLL_FRAC_HI Register (PLL_FRAC_HI)
The PLL_FRAC_HI register contains the 8 most significant bits of the PLL_FRAC scaled fraction. For the
definition of PLL_FRAC, see PLL in Section 3, Circuit Descriptions.
7
6
5
4
3
2
1
0
PLL__FRAC_HI[7:0]
0xB2—PLL_FRAC_LO Register (PLL_FRAC_LO)
The PLL_FRAC_LO register contains the 8 least significant bits of the PLL_FRAC scaled fraction. For the
definition of PLL_FRAC, see PLL in Section 3, Circuit Descriptions.
7
6
5
4
3
2
1
0
PLL__FRAC_LO[7:0]
4-14
Conexant
N8954DSC
Bt8954
4.0 Registers
4.7 PLL Configuration
Voice Pair Gain Framer
0xB3—PLL_A Register (PLL_A)
The PLL_A register contains the A part of scaling PLL_FRACP. For the definitions of PLL_A and
PLL_FRACP, see PLL in Section 3, Circuit Descriptions.
7
6
5
4
3
2
1
0
PLL_A[7:0]
0xB4—PLL_B Register (PLL_B)
The PLL_B register contains the B part of scaling PLL_FRACP. For the definitions of PLL_B and
PLL_FRACP, see PLL in Section 3, Circuit Descriptions.
7
6
5
4
3
2
1
0
PLL_B[7:0]
0xB5—PLL_SCALE Register (PLL_SCALE)
The PLL_SCALE register contains the PLL_X and PLL_C values for pre-scaling the PLL input and for
post-scaling the PLL output. PLL_P indicates the maximum microcomputer frequency the Bt8954 supports
(fGCLK/2). For the definitions of PLL_C, PLL_X, and PLL_P, see PLL in Section 3, Circuit Descriptions.
7
—
N8954DSC
6
5
PLL_P[1:0]
4
3
PLL_C[2:0]
Conexant
2
1
0
PLL_X[1]
PLL_X[0]
4-15
Bt8954
4.0 Registers
4.8 Common
Voice Pair Gain Framer
4.8 Common
Common Command Write registers are listed in Table 4-6.
Table 4-6. Common Command Write Registers
Address
Register Label
Bits
Name/Description
0xC0
CMD_1
7
Command
0xC1
REV_ID
3
Revision ID
0xC0—Command Register 1 (CMD_1)
7
6
5
—
PCMn_RANGE
EXTRA_Z_BIT
PCMn_RANGE
4
3
EXTRA_SIG_UPDATE[1:0]
2
1
0
DP_LOOP
PP_LOOP
SYNC_SLAVE
Indicates range for PCMn.
0 = PCM_8 → PCM18
(i.e., for PCM_FORMAT1 register: 8 < NUM_CHAN < 18)
1 = PCM1 → PCM7(1)
(i.e., for PCM_FORMAT1 register: 1 < NUM_CHAN < 7)
NOTE:
EXTRA_Z_BIT
Use PCMn_RANGE = 0 for PCM7 with 8 signaling bits (since PCM7 with 8
signaling bits is equivalent to PCM8 with 0 signaling bits).
If set, enables the transmit of an extra 8 kbps Z-bit field in the DSL frame.
0 = Basic DSL frame structure transmit
1 = Transmit extra Z-bit in each block of the DSL frame
4-16
Conexant
N8954DSC
Bt8954
4.0 Registers
4.8 Common
Voice Pair Gain Framer
EXTRA_SIG_
UPDATE[1:0]
Number of extra LD_TSIG/RD_RSIG signaling interrupts per 6 ms DSL frame in addition to
the normal signaling interrupt that occurs coincident with the DSL frame boundary.
00 = Default case: no extra signaling interrupt. Corresponds to one
signaling interrupt every 6 ms, coincident with the DSL frame boundary.
01 = One extra signaling interrupt. Corresponds to two signaling interrupts
every 6 ms, or one signaling interrupt every 3 ms. That is, one occurs
coincident with the DSL frame boundary, and the other occurs 3 ms
(or 24 payload blocks) later.
10 = Two extra signaling interrupts. Corresponds to three signaling
interrupts every 6 ms. That is, one signaling interrupt every 2 ms: one
occurs coincident with the DSL frame boundary, and the other two
signaling interrupts occur 2 ms (or 16 payload blocks) and 4 ms (or 32
payload blocks) later.
11 = Five extra signaling interrupts. Corresponds to six signaling
interrupts every 6 ms. That is, one signaling interrupt every 1 ms: one
occurs coincident with the DSL frame boundary, and the other five
signaling interrupts occur 1 ms (or 8 payload blocks), 2 ms (or 16 payload
blocks), 3 ms (24 payload blocks), 4 ms (or 32 payload blocks), and 5 ms
(or 40 payload blocks) later.
DP_LOOP
Loopback towards DSL on the PCM side—The PCMT input is replaced by data generated
from the receiver. The receiver operates normally, but the transmit PCMT is ignored.
0 = Normal PCM transmit operation
1 = Transmit PCM data supplied by the receiver
PP_LOOP
Loopback towards PCM on the PCM Side—The PCMR output is connected from the PCMT
input. Signals are switched directly at the I/O pins. DSL transmit and receive channels operate
normally, except the receive channel outputs are replaced by loopback signals.
0 = Normal PCM receive
1 = PCMR is supplied by PCM transmit input
SYNC_SLAVE
PCM Syncs slaved to the DSL receives sync when set to 1.
0 = PCM Sync Master
1 = Receive DSL Sync Master
0xC1—Revision Identification (REV_ID)
7
6
5
4
3
—
—
—
—
—
VER[2:0]
2
1
0
VER[2:0]
Version Number—Contains the device revision level which the MC can read to determine the
installed device.
000 = Bt8954 Rev A
001 = Bt8954 Rev B
010 = Bt8954 Rev C
N8954DSC
Conexant
4-17
Bt8954
4.0 Registers
4.9 Interrupt
Voice Pair Gain Framer
4.9 Interrupt
The Interrupt registers are listed in Table 4-7.
Table 4-7. Interrupt Registers
Address
Register Label
Bits
Name/Description
0xD0
ISR
8
Interrupt Status Register
0xD1
IMR
8
Interrupt Mask Register
0xD0—Interrupt Status Register (ISR)
The Interrupt Status register (ISR) consists of independent read/write interrupt flags, one for each of eight
internal sources. Each flag bit is set and stays set when its corresponding source indicates that a valid interrupt
event occurred (for edge-triggered interrupts) or a valid interrupt condition exists (for level-sensitive interrupts).
If unmasked, this event causes the IRQ* output to be activated. Writing a logic 0 to an interrupt flag causes the
flag to be immediately cleared. Attempting to clear a flag whose underlying condition still exists does not
immediately clear the flag, but allows it to remain set until the underlying condition expires, at which time the
flag is cleared automatically. The clearing of an unmasked flag causes the IRQ* output to return to an inactive
state, if no other unmasked interrupt flags are set.
7
6
5
4
3
2
1
0
SIG_FIFO_ERR
RD_RSIG
LD_TSIG
PLL_ERR
RX_ERR
RX
TX_ERR
TX
SIG_FIFO_ERR
Signaling FIFO Error Interrupt—Informs the MC that a signaling FIFO error has occurred
(TSFIFO_I_OVER or TSFIFO_I_UNDER or TSIFIFO_O_OVER or TSFIFO_O_UNDER or
RSFIFO_I_OVER or RSFIFO_I_UNDER or RSFIFO_O_OVER or RSFIFO_O_UNDER).
0 = No interrupt
1 = SIG_FIFO_ERR interrupt
RD_RSIG
Read Receive Signaling Interrupt—Instructs the MC to read new receive signaling
information before the next RD_RSIG interrupt occurs. This interrupt occurs every 6 ms,
3 ms, 2 ms, or 1 ms depending on the EXTRA_SIG_UPDATE configuration in the CMD_1
register [0xC0]. A RD_RSIG interrupt always occurs coincident with the start of the receive
DSL 6 ms frame, i.e., whenever an Rx interrupt occurs.
0 = No interrupt
1 = RD_RSIG interrupt
LD_TSIG
Load Transmit Signaling Interrupt—Instructs the MC to load new transmit signaling
information before the next LD_TSIG interrupt occurs. This interrupt occurs every 6 ms,
3 ms, 2 ms, or 1 ms depending on the EXTRA_SIG_UPDATE configuration in the CMD_1
register [0xC0]. A LD_TSIG interrupt always occurs coincident with the start of the transmit
DSL 6 ms frame, i.e., whenever a Tx interrupt occurs.
0 = No interrupt
1 = LD_TSIG interrupt
4-18
Conexant
N8954DSC
Bt8954
4.0 Registers
4.9 Interrupt
Voice Pair Gain Framer
PLL_ERR
PLL Error Interrupt—Indicates if PLL is in an out-of-lock state.
0 = PLL in-lock
1 = PLL out-of-lock
RX_ERR
Receive Error Interrupt—Framer state transition to OUT_OF SYNC, RFIFO errors; CRC and
FEBE counter overflows are logically ORed to form RX_ERR.
0 = No interrupt
1 = Receive error interrupt
Receive DSL 6 ms Frame Interrupt—Reported coincident with the start of the receive DSL
6 ms frame. This allows the MC to synchronize read access of the receive status registers.
RX
0 = No interrupt
1 = Receive frame interrupt
Transmit Error Interrupt—Generated whenever the Transmit HDSL frame is repositioned or a
TFIFO underflow/overflow error occurs.
TX_ERR
0 = No interrupt
1 = Transmit error interrupt/Transmit HDSL Frame Repositioned
Transmit DSL 6 ms Frame Interrupt—Reported coincident with the start of the transmit DSL
6 ms frame. This allows the MC to synchronize read access of the transmit status
[TSTATUS_1; 0xE7] and write access to the real-time transmit DSL registers.
TX
0 = No interrupt
1 = Transmit frame interrupt
0xD1—Interrupt Mask Register (IMR)
The Interrupt Mask register (IMR) consists of independent read/write mask bits for each ISR [0xD0] interrupt
flag. A logic 1 represents the masked condition, a logic 0 the unmasked condition. All mask bits behave
identically with respect to their corresponding interrupt flags. Setting a mask bit prevents the corresponding
interrupt flag from affecting the IRQ* output. Clearing a mask allows the interrupt flag to affect IRQ* output.
Unmasking an active interrupt flag immediately causes the IRQ* output to go active, if currently inactive.
Masking an active interrupt flag causes IRQ* to go inactive, if no other unmasked interrupt flags are set. Upon
RST* assertion, all IMR bits are automatically set to 1 to disable the IRQ* output.
7
6
5
4
3
2
1
0
SIG_FIFO_ERR
RD_RSIG
LD_TSIG
PLL_ERR
RX_ERR
RX
TX_ERR
TX
SIG_FIFO_ERR
Mask the SIG_FIFO_ERR interrupt.
RD_RSIG
Mask the RD_RSIG interrupt.
LD_TSIG
Mask the LD_TSIG interrupt.
PLL_ERR
Mask the PLL error interrupt.
RX_ERR
Mask the DSL receive error interrupt.
RX
Mask the DSL 6 ms receive frame interrupt.
TX_ERR
Mask the DSL transmit error interrupt.
TX
Mask the DSL 6 ms transmit frame interrupt.
N8954DSC
Conexant
4-19
Bt8954
4.0 Registers
4.10 Reset
Voice Pair Gain Framer
4.10 Reset
The Reset Write registers are listed in Table 4-8.
Table 4-8. Reset Write Registers
Address
Register Label
Name/Description
0xD3
SCR_RST
Scrambler Reset
0xD4
TFIFO_RST
Transmit FIFO Reset
0xD5
TSFIFO_PTR_RST
TSFIFO Pointer Reset
0xD6
RSFIFO_PTR_RST
RSFIFO Pointer Reset
0xD7
RFIFO_RST
Receive FIFO Reset
0xD8
SYNC_RST
Receive Framer Synchronization Reset
0xD9
ERR_RST
Error Count Reset
0xDA
RX_RST
Reset Receiver
0xDB
UPDATE_TSFIFO_O
Update TSFIFO_O
0xDC
UPDATE_RSFIFO
Update RSFIFO_O
0xD3—Scrambler Reset (SCR_RST)
Writing any data value to SCR_RST sets the 23 stages of the scrambler LFSR to 0x000001. SCR_RST is used
during Conexant production test to verify scrambler operation and is not required during normal operation.
0xD4—Transmit FIFO Reset (TFIFO_RST)
Writing any data value to TFIFO_RST empties the TFIFO. The MC must write TFIFO_RST whenever the
TFIFO reports an overflow or underflow [TSTATUS_1; 0xE7], and after the PLL has settled. Each write to
TFIFO_RST may cause up to three TFIFO errors to be reported in subsequent DSL frames. Therefore, the MC
must ignore up to three TFIFO errors reported after writing the TFIFO_RST command.
0xD5—Reset Pointer to Transmit Signaling FIFOs (TSFIFO_PTR_RST)
Writing any data value to TSFIFO_PTR_RST resets the pointer to the transmit signaling input FIFOs.
0xD6—Reset Pointer to Receive Signaling FIFOs (RSFIFO_PTR_RST)
Writing any data value to RSFIFO_PTR_RST resets the pointers to the receive signaling FIFOs.
4-20
Conexant
N8954DSC
Bt8954
4.0 Registers
4.10 Reset
Voice Pair Gain Framer
0xD7—Receive Elastic Store FIFO Reset (RFIFO_RST)
Writing any data value to RFIFO_RST empties the RFIFO and forces the payload mapper to realign DSL bytes
with respect to the receive DSL 6 ms frame. The MC must write RFIFO_RST whenever an RFIFO error is
reported [RSTATUS_1; 0xE5], and after the PLL has settled. Writing RFIFO_RST corrupts up to three receive
PCM frames worth of data.
0xD8—Receive Framer Synchronization Reset (SYNC_RST)
Writing any data value to SYNC_RST forces the receive framer to the OUT_OF_SYNC state, which restarts the
SYNC word search and causes the framer to issue an RX_ERR interrupt [ISR; 0xD0.3]. The MC must write
SYNC_RST after modifying FRAMER_EN [RCMD_1; 0x90.6], or SYNC_WORD. Writing SYNC_RST
corrupts up to three receive PCM frames worth of data.
0xD9—Error Count Reset (ERR_RST)
Writing any data value to ERR_RST clears the receive CRC Error Counter [CRC_CNT; 0xE8], the receive Far
End Block Error Counter [FEBE_CNT; 0x6E9] and consequently clears the counter overflow CRC_OVR and
FEBE_OVR bits [RSTATUS_2; 0xE6.6:7]. ERR_RST clears the error counters immediately and must be issued
within 6 ms after the respective receive frame interrupt in order to avoid clearing unreported errors. No other
receive errors (CRC_ERR or RFIFO) are affected by ERR_RST.
0xDA—Reset Receiver (RX_RST)
Writing any data value to RX_RST forces the PCM formatter to align the PCM receive timebase with respect to
the DSL channel’s receive 6 ms frame by reloading the RFIFO_WL value [0xA2, 0xA3]. The MC must write
RX_RST after modifying the RFIFO_WL value. Bt8954 automatically performs RX_RST each time the receive
framer changes alignment and transitions to the IN_SYNC state, if the EN_AUTO_RFIFO_RST is set.
Issuing RX_RST while the PCM formatter is aligned causes no change in alignment of the PCM receive
timebase.
0xDB—Update TSFIFO_O (UPDATE_TSFIFO_O)
Writing any data value to UPDATE_TSFIFO_O initiates a copy of TSFIFO_I into TSFIFO_O. This is only used
for testing.
0xDC—Update RSFIFO_O (UPDATE_RSFIFO_O)
Writing any data value to UPDATE_RSFIFO_O initiates a copy of RSFIFO_I into RSFIFO_O. This is only
used for testing.
N8954DSC
Conexant
4-21
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
4.11 Receive/Transmit Status
The MC can read all Receive and Transmit Status registers non-destructively at any time. All status registers are
updated coincident with the DSL channel’s receive or transmit 6 ms frame interrupts indicated in the Interrupt
Status Register [ISR; 0xD0]. Therefore, the MC can poll the ISR or enable interrupts to determine if a status
update has occurred. Real-time receive status (REOC, RIND, and RSBIT) register updates are suspended when
the receive framer reports an OUT_OF_SYNC state [RSTATUS_2; 0xE6]. The Receive and Transmit Status
Read registers are listed in Table 4-9.
Table 4-9. Receive and Transmit Status Read Registers
Address
Register Label
Bits
Register Description
0xE0
REOC_LO
8
Receive EOC Bits
0xE1
REOC_HI
5
Receive EOC Bits
0xE2
RIND_LO
8
Receive IND Bits
0xE3
RIND_HI
5
Receive IND Bits
0xE4
RSFIFO_I, RSFIFO_O
48 x 8, 48 x 8
Receive Signaling FIFOs
0xE5
RSTATUS_1
8
Receive Status 1
0xE6
RSTATUS_2
8
Receive Status 2
0xE7
TSTATUS_1
8
Transmit Status
0xE8
CRC_CNT
8
CRC Error Count
0xE9
FEBE_CNT
8
Far End Block Error Count
0xE0, 0xE1—Receive Embedded Operations Channel (REOC_LO, REOC_HI)
Receive EOC holds 13 EOC bits received during the previous DSL frame. Refer to Table 3-1 on page 3-3 for
EOC bit positions within the frame. The most significant bit, REOC[12] is received first.
REOC_LO (Address 0xE0)
7
6
5
4
3
2
1
0
11
10
9
8
REOC[7:0]
REOC_HI (Address 0xE1)
15
14
13
—
—
—
12
REOC[12:8]
0xE2, 0xE3—Receive Indicator Bits (RIND_LO, RIND_HI)
Receive IND holds 13 IND bits received during the previous DSL frame. Refer to Table 3-1 on page 3-3 for the
IND bit positions within the frame. The receive framer updates the RIND registers on receive frame interrupt
boundaries. The most significant bit RIND[12] is received first.
4-22
Conexant
N8954DSC
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
RIND_LO (Address 0xE2)
7
6
5
4
3
2
1
0
11
10
9
8
RIND[7:0]
RIND_HI (Address 0xE3)
15
14
13
—
—
—
12
RIND[12:8]
0xE4—Receive Signaling FIFOs (RSFIFOs)
RSFIFO_I[48:1],
and RSFIFO_O[48:1] Employing
a double-buffering scheme, two 48-byte FIFOs, receive signaling input FIFO
(RSFIFO_I), and receive signaling output FIFO (RSFIFO_O) are used to receive signaling
information, as illustrated in Figure 4-3.
Figure 4-3. Receive Signaling FIFOs
TEST_RS FIFO
From
Receiver
V
TEST_RSFIFO
To
MC
RSFIFO_I[48]
•
•
•
•
•
•
O
I
I
RSFIFO_0[2]
RSFIFO_I[2]
RSFIFO_0[1]
RSFIFO_I[1]
RD_RSIG(1)
OUT_OF_SYNC
O
UPDATE_RSFIFO_O(2)
V
RSFIFO_0[48]
From MC(3)
NOTE(S):
(1)
From Receiver
From MC; for testing only
(3)
For testing only
(2)
N8954DSC
Conexant
4-23
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
The number of signaling bits is set in TCM2_2 address [0x87]. The LSB of the signaling
bits is always in the LSB of the RSFIFO, as illustrated in Figure 4-4.
Up to 48 bytes of receive signaling information are loaded into RSFIFO_I by the receiver
after every RD_RSIG interrupt, provided that the framer is not in an OUT_OF_SYNC state.
RSFIFO_I[1] is received first. Up to 48 bytes of receive signaling information can be read
from RSFIFO_O by the MC after it receives the RD_RSIG interrupt. The MC has 6 ms, 3 ms,
2 ms, or 1 ms (depending on the EXTRA_SIG_UPDATE configuration in the CMD_1 register
[0x3C0.3:4]) from the current RD_RSIG to the next RD_RSIG to read 48, 24, 16, or 8
RSFIFO_O entries. RSFIFO_I is loaded into RSFIFO_O at every RD_RSIG interrupt, before
RSFIFO_I is modified by the receiver.
MC access to RSFIFO_O is provided by first writing to RSFIFO_PTR_RST [0xC6] to reset
the read pointer, and then reading up to 48 entries sequentially. RSFIFO_O[1] is read first.
Bt8954 increments the RSFIFO_O read pointer after read cycle. The pointer wraps around to
point to first entry (RSFIFO_O[1]) after the 48th entry (RSFIFO_O[48]) has been read.
Therefore, the RSFIFO_O read pointer needs to be reset only once (that is, during
initialization) if 48 entries are read every 6 ms.
For testing purposes, MC write access to RSFIFO_I is provided by first writing to
RSFIFO_PTR_RST [0xC6] to reset the RSFIFO_I write pointer, and then writing up to 48
entries sequentially. RSFIFO_I[1] is written first.
Bt8954 increments the RSFIFO_I write pointer after each write access to the RSFIFO’s
address. The pointer wraps around to point to the first entry (RSFIFO_I[1]) after the 48th
entry (RSFIFO_I[48]) has been written.
Also, for testing, writing any value to the UPDATE_RSFIFO_O register [0xDC] initiates
copying RSFIFO_I into RSFIFO_O, provided the TEST_RSFIFO bit in RCMD_2 [0x91] is
set.
Figure 4-4. Example of Three Signaling Bits
RSFIFO
TSFIFO
MSB
LSB
MSB
1 2 3 X X X X X
LSB
X X X X X 1 2 3
0xE5—Receive Status 1 (RSTATUS_1)
7
6
5
4
3
2
1
0
—
TR_INVERT
RSFIFO_O_
UNDER
RSFIFO_O_
OVER
RSFIFO_I_
UNDER
RSFIFO_I_OVER
RFIFO_UNDER
RFIFO_OVER
TR_INVERT
Tip/Ring Inversion—Indicates the receive framer acquired an inverted SYNC word A or B,
indicating the receive tip and ring wire pair connections are reversed. Bt8954 automatically
inverts the sign bits of all received data as it is presented on the RDAT input when inversion is
detected. TR_INVERT is updated each time the receive framer state transitions from
OUT_OF_SYNC to SYNC_ACQUIRED.
0 = SYNC_ACQUIRED with expected SYNC word
1 = SYNC_ACQUIRED with inverted SYNC word
4-24
Conexant
N8954DSC
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
RSFIFO_O_UNDER
Receive Signaling Input FIFO_UNDER Error—Indicates that RSFIFO_O has underflowed.
That is, RSFIFO_O is being read by the MC faster than it is being updated with RSFIFO_I.
Also reported in ISR (as part of SIG_FIFO_ERR) and generates a SIG_FIFO_ERR interrupt
(if SIG_FIFO_ERR in IMR is enabled).
0 = RSFIFO_O normal
1 = RSFIFO_O underflowed
RSFIFO_O_OVER
Receive Signaling Input FIFO_OVER Error—Indicates that RSFIFO_O has overflowed. That
is, RSFIFO_O is being updated faster than read by the MC. Also reported in ISR (as part of
SIG_FIFO_ERR) and generates a SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is
enabled).
0 = RSFIFO_O normal
1 = RSFIFO_O overflowed
RSFIFO_I_UNDER
Receive Signaling Input FIFO_UNDER Error—Indicates that RSFIFO_I has underflowed.
That is, RSFIFO_I is being copied into RSFIO_O faster than it is being updated (from receive
DSL frames). Also reported in ISR (as part of SIG_FIFO_ERR) and generates a
SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is enabled). RSFIFO_I_UNDER
cannot be permanently cleared. Writing any value to RSFIFO_PTR_RST [0x06] can
temporarily clear this error. On the next RD-RSIG interrupt, RSFIFO_I_UNDER is again set.
0 = RSFIFO_I normal
1 = RSFIFO_I underflowed
RSFIFO_I_OVER
Receive Signaling Input FIFO_OVER Error—Indicates that RSFIFO_I has overflowed. That
is, RSFIFO_I is being updated faster (from receive DSL frames) than it is being copied into
RSFIFO_O. Also reported in ISR (as part of SIG_FIFO_ERR) and generates a
SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is enabled).
0 = RSFIFO_I normal
1 = RSFIFO_I overflowed
RFIFO_UNDER
Receive FIFO_UNDER Error—Indicates the RFIFO has underrun. Also reported in ISR and
generates an RX_ERR interrupt (if RX_ERR in IMR is enabled). RFIFO_UNDER is
indicative of clock problems and may be triggered by events similar to those which cause
RFIFO_OVER errors.
0 = RFIFO normal
1 = RFIFO underrun
RFIFO_OVER
Receive FIFO_OVER Error—Indicates the RFIFO has overflowed. Also reported in ISR and
generates an RX_ERR interrupt (if RX_ERR in IMR is enabled). RFIFO_OVER is indicative
of clock problems.
0 = RFIFO normal
1 = RFIFO overflowed
N8954DSC
Conexant
4-25
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
0xE6—Receive Status 2 (RSTATUS_2)
7
6
5
FEBE_OVR
CRC_OVR
CRC_ERR
FEBE_OVR
4
3
2
SYNC_STATE[1:0]
1
0
STATE_CNT[2:0]
Far End Block Error Count Overflow—Indicates the FEBE count [FEBE_CNT; 0x69] has
reached its maximum value of 255. Generates an RX_ERR interrupt.
0 = FEBE count below maximum
1 = FEBE count equals maximum 255 (0xFF)
CRC_OVR
CRC Error Count Overflow—Indicates the CRC error count [CRC_CNT; 0xE8] has reached
its maximum value of 255, and generates an RX_ERR interrupt.
0 = CRC error count below maximum
1 = CRC error count equals maximum 255 (0xFF)
CRC_ERR
CRC Error—Shows that the CRC comparison in the previous frame resulted in a mismatch of
one or more CRC bits. CRC_ERR is invalid in the OUT_OF_SYNC state. The MPU can copy
CRC_ERR into the first transmit IND [TIND_LO; 0x82] to report FEBE.
0 = CRC pass
1 = CRC error detected
SYNC_STATE[1:0]
Receive Framer Synchronization State—Reports the state of the receive framer. Refer to
Figure 3-4 on page 3-6.
00
01
10
11
OUT_OF_SYNC
SYNC_ACQUIRED
IN_SYNC
SYNC_ERRORED
When the framer enters OUT_OF_SYNC, the RFIFO is automatically reset, FEBE and
CRC error counts are suspended, and RX_ERR is activated.
When the framer reports SYNC_ACQUIRED, the RFIFO and the payload mapper are
enabled, and RX_ERR is activated.
When the framer enters IN_SYNC, the RFIFO water level [RFIFO_WL; 0xA2, 0xA3] is
re-established, FEBE and CRC counting resumes, and RX_ERR is activated.
When the framer reports SYNC_ERRORED, STATE_CNT indicates the number of
consecutive frames in which SYNC was not detected.
STATE_CNT[2:0]
Intermediate State Count—Applicable only if SYNC_STATE reports SYNC_ACQUIRED or
SYNC_ERRORED states. STATE_CNT indicates the framer’s progress through the
intermediate states.
000
001
010
011
100
101
110
111
4-26
1 frame
2 consecutive frames
3 consecutive frames
4 consecutive frames
5 consecutive frames
6 consecutive frames
7 consecutive frames
8 consecutive frames
Conexant
N8954DSC
Bt8954
4.0 Registers
4.11 Receive/Transmit Status
Voice Pair Gain Framer
0xE7—Transmit Status 1 (TSTATUS_1)
7
6
5
4
3
2
1
0
—
—
TSFIFO_O_ UNDER
TSFIFO_O_ OVER
TSFIFO_I_UNDER
TSFIFO_I_OVER
TFIFO_UNDER
TFIFO_OVER
TSFIFO_O_UNDER
Transmit Signaling Output FIFO_UNDER Error—Indicates that the TSFIFO_O has
underflowed. That is, TSFIFO_O is being read into DSL frames faster than it is being updated
with TSFIFO_I. Also reported in ISR (as part of SIG_FIFO_ERR), this error generates a
SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is enabled).
0 = TSFIFO_O normal
1 = TSFIFO_O underflowed
TSFIFO_O_OVER
Transmit Signaling Output FIFO_OVER Error indicates that TSFIFO_O has overflowed. That
is, the TSFIFO_O is being updated faster than it is being read and transmitted in DSL frames.
Also, reported in ISR (as part of SIG_FIFO_ERR), this error generates a SIG_FIFO_ERR
interrupt (if SIG_FIFO_ERR in IMR is enabled).
0 = TSFIFO_O normal
1 = TSFIFO_O overflowed
TSFIFO_I_UNDER
Transmit Signaling Input FIFO_UNDER Error—Indicates that the TSFIFO_I has
underflowed. That is, TSFIFO_I is being copied into TSFIFO_O faster than it is being updated
by the MC. Also reported in ISR (as part of SIG_FIFO_ERR), this error generates a
SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is enabled).
0 = TSFIFO_I normal
1 = TSFIFO_I underflowed
TSFIFO_I_OVER
Transmit Signaling Input FIFO_OVER Error—Indicates that the TSFIFO_I has overflowed.
That is, the TSFIFO_I is being updated faster by the MC than it is being copied into
TSFIFO_O. Also reported in ISR (as part of SIG_FIFO_ERR), this error generates a
SIG_FIFO_ERR interrupt (if SIG_FIFO_ERR in IMR is enabled).
0 = TSFIFO_I normal
1 = TSFIFO_I overflowed
TFIFO_UNDER
Transmit FIFO_UNDER Error—Indicates the TFIFO has underrun. Also reported in ISR, this
error generates a TX_ERR interrupt (if TX_ERR in IMR is enabled).
0 = TFIFO normal
1 = TFIFO underrun
TFIFO_OVER
Transmit FIFO_OVER Error—Indicates the TFIFO has overflowed. Also reported in ISR, this
error generates a TX_ERR interrupt (if TX_ERR in IMR is enabled).
0 = TFIFO normal
1 = TFIFO overflowed
N8954DSC
Conexant
4-27
Bt8954
4.0 Registers
4.12 PCM Formatter
Voice Pair Gain Framer
0xE8—CRC Error Count (CRC_CNT)
7
6
5
4
3
2
1
0
CRC_CNT[7:0]
CRC_CNT[7:0]
CRC Error Count—Indicates the total number of received CRC errors detected by the receive
framer and increments by one for each received DSL 6 ms frame that contains CRC_ERR
[RSTATUS_2; 0xE6]. CRC_CNT is cleared to 0 by ERR_RST [0xD9], and error counting is
suspended while the receive framer is OUT_OF_SYNC or SYNC_ACQUIRED. CRC_CNT
also sets CRC_OVR [RSTATUS_2; 0xE6] upon reaching its maximum count value of 255.
0xE9—Far End Block Error Count (FEBE_CNT)
7
6
5
4
3
2
1
0
FEBE_CNT[7:0]
FEBE_CNT[7:0]
Far End Block Error Count—Indicates the total number of received FEBE errors sent by the
far end transmitter and increments by one for each received DSL 6 ms frame that contains an
active (low) FEBE bit. FEBE is the second IND bit received within the Indicator bit group and
can be monitored separately as the RIND[1] bit in the RIND_LO [0xE2] Receive Status
register. Refer to the DSL Frame Format subsection, Table 2, for the FEBE bit position within
the frame. FEBE_CNT is reset to 0 by ERR_RST [0xD9], and error counting is suspended
while the receive framer is OUT_OF_SYNC or SYNC_ACQUIRED. FEBE_CNT also sets
FEBE_OVR [RSTATUS_2; 0xE6] upon reaching its maximum count value of 255.
4.12 PCM Formatter
The PCM Formatter registers are listed in Table 4-10.
Table 4-10. PCM Formatter Register Summary
4-28
Address
Register Label
Bits
Register Description
0xF0
PFRAME_LEN
8
PCM Frame Length
0xF1
PCM_FORMAT
8
PCM Format
Conexant
N8954DSC
Bt8954
4.0 Registers
4.12 PCM Formatter
Voice Pair Gain Framer
0xF0—PCM Frame Length (PFRAME_LEN)
7
6
5
4
3
2
1
0
PFRAME_LEN[7:0]
PFRAME_LEN[7:0]
PCM Frame Length contains the number of bits in one 125 µs PCM frame less 1. The selected
value is given by
8 x (# time slots in 125 µs PCM frame) –1
if PCM_FREQ (PCM_FORMAT1; addr 0xF1) = 0,
PFRAME_LEN = 8 x 32 –1 = 255
if PCM_FREQ (PCM_FORMAT1; 0xF1) = 1,
PFRAME_LEN = 8 x 24–1 = 191
0xF1—PCM Format (PCM_FORMAT1)
7
6
5
PCM_FREQ
ENC_FSYNC
COMPRESSED
PCM_FREQ
4
3
2
1
0
NUM_CHAN[4:0]
PCMCKI frequency.
0 : fPCMCKI = 2.048 MHz
1 : fPCMCKI = 1.536 MHz
ENC_FSYNC
Indicates if PCMF[6:1] contains encoded PCM frame syncs. If ENC_FSYNC is 1, PCMF[6:1]
is encoded.
0 = PCMF[6:1] is decoded
1 = Encoded PCMF[6:1]
ENC_FSYNC must be programmed as 1 if the number of compressed voice channels
exceeds 18, the total number of available PCMF pins. For example, if NUM_CHAN = 10 and
COMPRESSED = 1, ENC_FSYNC must be 1, since 20 (the number of PCMF strobes needed
to represent 20 compressed voice channels) is greater than 18, which is the number of available
PCMF pins.
COMPRESSED
Indicates if each time slot carries one 64 kbps clear voice channel or carries two 32 kbps
compressed voice channels.
0 = All channels are clear
1 = All channels are compressed
NUM_CHAN[4:0]
Number of used PCM time slots. Satisfies the following inequality:
1 <= NUM_CHAN[4:0] <= 18
N8954DSC
Conexant
4-29
Bt8954
4.0 Registers
4.12 PCM Formatter
4-30
Voice Pair Gain Framer
Conexant
N8954DSC
5
5.0 Electrical and Mechanical
Specifications
5.1 Electrical Specifications
5.1.1 Absolute Maximum Ratings
The absolute maximum ratings are listed in Table 5-1.
Table 5-1. Absolute Maximum Ratings
Symbol
VDD
VI
TST
TVSOL
θJA
Parameter
Minimum
Maximum
Units
Supply Voltage
–0.3
7
V
Voltage on Any Signal Pin
–1.0
VDD+0.3
V
Storage Temperature
–40
125
°C
Vapor Phase Soldering Temperature (1 minute)
—
220
°C
Thermal Resistance (68 PLCC), Still Air
—
39.8
°C
/W
NOTE(S): Stresses greater than those listed in this table may cause permanent damage to the device. This is a
stress rating only. Functional operation of the device at these or any other conditions beyond those listed in the
operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
5.1.2 Recommended Operating Conditions
The recommended operating conditions are listed in Table 5-2.
Table 5-2. Recommended Operating Conditions
Symbol
Parameter
Minimum
Maximum
Units
VDD
Supply Voltage
4.75
5.25
V
TAMB
Ambient Operating Temperature
–40
85
°C
VIH
High-Level Input Voltage
2.0
VDD+0.3
V
VIL
Low-Level Input Voltage for TCK@ 25°C
Low-Level Input Voltage for All Other Inputs
-0.3
-0.3
0.4
0.8
V
V
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
5.1.3 Electrical Characteristics
The electrical characteristics are listed in Table 5-3.
Table 5-3. Electrical Characteristics
Symbol
Parameter
Minimum
Maximum
Units
IDD
Supply Current @ fGCLK = 25 MHz
Supply Current @ fGCLK = 33 MHz
Supply Current @ fGCLK = 50 MHz
—
55
70
100
mA
mA
mA
VOH
High-Level Output Voltage @ IOH = –200 uA
2.4
—
V
VOL
Low-Level Output Voltage @ IOL = 2 mA
Low-Level IRQ* Output Voltage @ IOD = 1.0 mA
—
0.4
0.4
V
V
IPR
Resistive Pullup Current
40
500
µA
Input Leakage Current
–10
10
µA
IOZ
Three-State Leakage Current
–10
10
µA
CIN
Input Capacitance
—
2.5
pF
CLD
Output Capacitive Loading
—
70
pF
CZ
High-Impedance Output Capacitance
—
85
pF
II
5.1.4 DSL Interface Timing
The QCLK timing requirements are displayed in Table 5-4. QCLK timing and
DSL interface timing are illustrated in Figures 5-1 and 5-2.
Table 5-4. QCLK Timing Requirements
Symbol
Parameter
Minimum
Maximum
Units
1
QCLK Frequency
0.080
0.584
MHz
2
Clock Width High
Tqclk/2 – 20
Tqclk/2 + 20
ns
3
Clock Width Low
Tqclk/2 – 20
Tqclk/2 + 20
ns
Figure 5-1. QCLK Timing
QCLK
2
3
1
5-2
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5.1 Electrical Specifications
Voice Pair Gain Framer
Table 5-5. DSL Interface Switching Characteristics
Symbol
Parameter
Minimum
Maximum
Units
4
TDAT Setup Prior to BCLK Falling Edge
100
—
ns
5
TDAT Hold After BCLK Low
25
—
ns
6
BCLK Period
TQCLK ÷ 2
TQCLK ÷ 2
—
7
BCLK Pulse-Width High
TQCLK ÷ 4 – 20
TQCLK ÷ 4 + 20
ns
8
BCLK Pulse-Width Low
TQCLK ÷ 4 – 20
TQCLK ÷ 4 + 20
ns
9
RDAT, QCLK Hold after BCLK Rising Edge
–50
—
ns
10
RDAT, QCLK Delay after BCLK High
—
50
ns
Figure 5-2. DSL Interface Timing
6
7
BCLK
8
10
9
QCLK
RDAT
4
5
TDAT
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
5.1.5 PCM Interface Timing
PCM interface switching characteristics are displayed in Table 5-6.
Table 5-6. PCM Interface Switching Characteristics
Symbol
Parameter
Minimum
Maximum
Units
11
PCMCLK Frequency
1.536
2.048
MHz
12
PCMCLK Rise Time
—
50
ns
13
PCMCLK Fall Time
—
50
ns
14
Setup Time, PCMFn High before PCMCLK Falling Edge
50
—
ns
15
Hold Time, PCMFn High after PCMCLK Falling Edge
50
—
ns
16
Delay Time, PCMCLK High to PCMT Data Valid
0
140
ns
17
Setup Time, PCMR Valid before PCMCLK Falling Edge
50
—
ns
18
Hold Time, PCMR Valid after PCMCLK Falling Edge
If Gclk = 33 MHz—Hold Time, PCMR Valid after PCMCLK Falling Edge
If Gclk = 50 MHz—Hold Time, PCMR Valid after PCMCLK Falling Edge
30.4
18.5
50
50
ns
ns
50
165
ns
19
Delay Time, PCMCLK Low to PCMT Data Disabled
PCM interface timing is illustrated in Figure 5-3.
Figure 5-3. PCM Interface Timing
PCMCLK
12
17
13
11
16
1
PCMT
2
3
4
5
6
19
8
7
1
15
18
PCMR
1
2
3
4
5
18
6
7
8
1
14
PCMFn
(Short
Frame
Sync)
Transmit and Receive Bytes for Codec n
PCMFn+1
(Short
Frame
Sync)
5-4
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
5.1.6 Microcomputer Interface Timing
Microcomputer interface timing and switching requirements are displayed in
Tables 5-6 and 5-7.
MCI write timing, Intel mode (MOTEL = 0) is illustrated in Figure 5-4.
MCI write timing, Motorola mode (MOTEL = 1) is illustrated in Figure 5-5.
MCI read timing, Intel mode (MOTEL = 0) is illustrated in Figure 5-6.
MCI read timing, Motorola mode (MOTEL = 1) is illustrated in Figure 5-7.
Internal write timing is illustrated in Figure 5-8.
Table 5-7. Microcomputer Interface Timing Requirements
Symbol
Parameter
Minimum
Maximum
Units
20
ALE Pulse-Width High
30
—
ns
21
Address Setup Prior to ALE Falling Edge
15
—
ns
22
Address Hold after ALE Low
5
—
ns
23
ALE Low Prior to Write Strobe Falling Edge(1)
20
—
ns
24
Write Strobe Pulse-Width Low(1)
40
—
ns
25
Read Strobe Pulse-Width Low(2)
50
—
ns
26
Data in Setup Prior to Write Strobe Rising Edge(1)
30
—
ns
27
Data in Hold after Write Strobe High(1)
5
—
ns
28
R/W* Setup Prior to Read/Write Strobe Falling Edge
10
—
ns
29
R/W* Hold after Read*/Write Strobe* High
10
—
ns
30
ALE Falling Edge after Write Strobe* High
20
—
ns
31
ALE Falling Edge after Read Strobe* High
20
—
ns
32
RST* Pulse-Width Low
50
—
ns
NOTE(S):
(1)
(2)
In Intel mode, Write Strobe* is defined as (WR* or CS*). In Motorola mode, it is defined as (DS or CS) when R/W is low.
In Intel mode, Read Strobe* is defined as (RD* or CS). In Motorola mode, it is defined as (DS or CS) when R/W is high.
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5.1 Electrical Specifications
Voice Pair Gain Framer
Table 5-8. Microcomputer Interface Switching Characteristics
Symbol
Parameter
Minimum
Maximum
Units
33
Data Out Enable (Low Z) after Read Strobe* Falling Edge(1)
2
—
ns
34
Data Out Valid after Read Strobe* Low(1)
—
50
ns
35
Data Out Hold after Read Strobe* Rising Edge(1)
2
—
ns
36
Data Out Disable (High Z) after Read Strobe* High(1)
—
25
ns
37
IRQ* Hold after Write Strobe* Rising Edge(2,3)
5
—
ns
38
IRQ* Delay after Write Strobe* High(2,3)
—
TQCLK ÷ 32 + 20
ns
39
Internal Register Delay after Write Strobe* High(3)
—
TQCLK ÷ 32
—
40
Internal RAM Delay after Write Strobe* High(3)
—
2 x TQCLK
—
41
Access Data Register Delay after Write Strobe* High(3)
—
2 x TQCLK
—
NOTE(S):
(1)
Read Strobe* is defined as RD* or CS* in Intel mode, and DS* or CS* when R/W* is high in Motorola mode.
When writing an interrupt mask or status register.
(3)
Write Strobe* is defined as WR* or CS* in Intel mode, and DS* or CS* when R/W* is low in Motorola mode.
(2)
Figure 5-4. MCI Write Timing, Intel Mode (MOTEL = 0)
AD[7:0]
Address
21
Data (Input)
22
26
27
Write
Strobe*
23
24
20
30
ALE
5-6
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5.1 Electrical Specifications
Voice Pair Gain Framer
Figure 5-5. MCI Write Timing, Motorola Mode (MOTEL = 1)
AD[7:0]
Address
21
Data (Input)
22
26
27
Write
Strobe*
23
24
R/W*
29
28
20
30
ALE
Figure 5-6. MCI Read Timing, Intel Mode (MOTEL = 0)
AD[7:0]
Address
21
Data (Output)
22
20
22
23
21
Read
Strobe*
25
20
31
ALE
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
Figure 5-7. MCI Read Timing, Motorola Mode (MOTEL = 1)
Address
AD[7:0]
21
Data (Output)
33
22
35
34
36
Read
Strobe*
25
29
28
R/W*
20
31
ALE
Figure 5-8. Internal Write Timing
Write
Strobe*
38
37
IRQ*
39
Internal
Register
40
Internal
RAM
41
Access
Data
Register
5-8
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
5.1.7 Test and Diagnostic Interface Timing
Test and diagnostic interface timing and switching requirements are displayed in
Tables 5-8 and 5-9. JTAG interface timing is illustrated in Figure 5-9.
Table 5-9. Test and Diagnostic Interface Timing Requirements
Symbol
Parameter
Minimum
Maximum
Units
42
TCK Pulse-Width High
80
—
ns
43
TCK Pulse-Width Low
80
—
ns
44
TMS, TDI Setup Prior to TCK Rising Edge(1)
20
—
ns
45
TMS, TDI Hold after TCK High(1)
20
—
ns
Minimum
Maximum
Units
NOTE(S):
(1)
Also applies to functional inputs for SAMPLE/PRELOAD and EXTEST instructions.
Table 5-10. Test and Diagnostic Interface Switching Characteristics
Symbol
Parameter
46
TDO Hold after TCK Falling Edge(1)
0
—
ns
47
TDO Delay after TCK Low(1)
—
50
ns
48
TDO Enable (Low Z) after TCK Falling Edge(1)
2
—
ns
49
TDO Disable (High Z) after TCK Low(1)
—
25
ns
NOTE(S): The Test and Diagnostic Interface of the Bt8954 has not yet been fully characterized; therefore, it it not being tested
according to the VIH, VIL, VOH, and VOL parameters as listed. This interface is for testing only.
Figure 5-9. JTAG Interface Timing
TDO
46
48
42
49
47
TCK
44
45
43
TDI
TMS
M
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5.0 Electrical and Mechanical Specifications
5.1 Electrical Specifications
Voice Pair Gain Framer
The input waveforms are illustrated in Figure 5-10. Output waveforms are
illustrated in Figure 5-11 and Figure 5-12.
Figure 5-10. Input Waveforms for Timing Tests
3V
2.0 V
0.8 V
0V
Input
High
Input
Low
Input
Low
Input
High
Figure 5-11. Output Waveforms for Timing Tests
≈VDD
2.4 V
0.4 V
≈0 V
Output
High
Output
Low
Output
Low
Output
High
Figure 5-12. Output Waveforms for Three-State Enable and Disable Tests
VOH - 0.2 V
1.7 V
1.5 V
1.3 V
VOL + 0.2 V
Output
Disabled
5-10
Output
Enabled
Conexant
Output
Disabled
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5.0 Electrical and Mechanical Specifications
5.2 Mechanical Specifications
Voice Pair Gain Framer
5.2 Mechanical Specifications
The 68-pin PLCC package is illustrated in Figure 5-13.
Figure 5-13. 68-Pin PLCC Package Drawing
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5.0 Electrical and Mechanical Specifications
5.2 Mechanical Specifications
5-12
Voice Pair Gain Framer
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A
Appendix A: Applications
This chapter shows typical interconnections of the Bt8954 Voice Pair Gain
Framer to the following devices:
• Bt8960 MDSL Transceiver or Bt8970 HDSL Transceiver
• Texas Instrument TP3054A PCM Codec
• Motorola 68302 16-bit Processor
• Intel 8051 8-bit Processor
A.1 Interfacing to the Bt8960/Bt8970 HDSL
Transceiver
A typical interconnection between the Bt8954 and the Bt8960/Bt8970 is
illustrated in Figure A-1.
Figure A-1. Bt8954 to Bt8960/Bt8970 DSL Transceiver Interconnection
VDD
Bt8960/Bt8970
Bt8954
TQ[0]
RQ[1]/RDAT
RQ[0]/BCLK
Note:
RDAT
100Ω
BCLK
QCLK
QCLK
TQ[1]/TDAT
TDAT
When low, the Loop Quat Clock (QCLK) qualifies the sign bit on the Loop Receive Data (RDAT).
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Appendix A : Applications
A.2 Interfacing to the Texas Instrument TP3054A PCM Codec
Voice Pair Gain Framer
A.2 Interfacing to the Texas Instrument TP3054A
PCM Codec
A typical interconnection between the Bt8954 and the Texas Instrument TP3054A
PCM Codec is illustrated in Figure A-2.
Figure A-2. Bt8954 to Texas Instrument TP3054A PCM Codec Interconnection
PCMCLK
MCLKX
BCLKX
FSR
PCMFn
Bt8954
PCMR
FSX
DR
PCMT
DX
TP3054A
BCLKR/CLKSEL
MCLKR/PDN
A-2
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Appendix A : Applications
A.3 Interfacing to the Motorola 68302 16-Bit Processor
Voice Pair Gain Framer
A.3 Interfacing to the Motorola 68302 16-Bit
Processor
A typical interconnection between the Bt8954 and the Motorola 68302 Processor
is illustrated in Figure A-3.
Figure A-3. Bt8954 to Motorola 68302 Processor Interconnection
VDD
MOTEL*
IRQ*
IRQ6*
MC68302
A[15]
CS*
AS*
ALE
DS*
RD*
R/W*
A[6:0]
WR*/R/W*
D[7:0]
AD[7:0]
Bt8954
ADDR[6:0]
VDD
MUXED
DTACK*
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Appendix A : Applications
A.4 Interfacing to the Intel 8051 8-Bit
Voice Pair Gain Framer
A.4 Interfacing to the Intel 8051 8-Bit
A typical interconnection between the Bt8954 and the Intel 8051 Controller is
illustrated in Figure A-4.
Figure A-4. Bt8954 to Intel 8051 Controller Interconnection
MOTEL*
8051
Bt8954
AD[15]
CS*
ALE
ALE
WR
WR*
RD
RD*
AD[7:0]
AD[7:0]
VDD
VDD
INT0
MUXED
IRQ*
A.5 References
Applicable specifications are listed here:
•
•
•
•
•
A-4
Bellcore TA-NWT-001210
Bellcore FA-NWT-001211
ETSI RTR/TM–03036
ITU–T Recommendation G.704
Bellcore TR-NWT-000499
Conexant
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