Data Sheet

SC68C752B
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte
FIFOs and 68 mode μP interface
Rev. 04 — 20 January 2010
Product data sheet
1. General description
The SC68C752B is a dual Universal Asynchronous Receiver/Transmitter (UART) with
64-byte FIFOs, automatic hardware/software flow control, and data rates up to 5 Mbit/s.
The SC68C752B offers enhanced features. It has a Transmission Control Register (TCR)
that stores receiver FIFO threshold levels to start/stop transmission during hardware and
software flow control. With the FIFO Rdy register, the software gets the status of
TXRDYn/RXRDYn for all four ports in one access. On-chip status registers provide the
user with error indications, operational status, and modem interface control. System
interrupts may be tailored to meet user requirements. An internal loopback capability
allows on-board diagnostics.
The UART transmits data, sent to it over the peripheral 8-bit bus, on the TXn signal and
receives characters on the RXn signal. Characters can be programmed to be 5 bits, 6 bits,
7 bits, or 8 bits. The UART has a 64-byte receive FIFO and transmit FIFO and can be
programmed to interrupt at different trigger levels. The UART generates its own desired
baud rate based upon a programmable divisor and its input clock. It can transmit even,
odd, or no parity and 1, 1.5, or 2 stop bits. The receiver can detect break, idle, or framing
errors, FIFO overflow, and parity errors. The transmitter can detect FIFO underflow. The
UART also contains a software interface for modem control operations, and has software
flow control and hardware flow control capabilities.
The SC68C752B is available in LQFP48 and HVQFN32 packages.
2. Features
„
„
„
„
„
„
„
„
„
Dual channel with 68 mode (Motorola) μP interface
Up to 5 Mbit/s data rate
64-byte transmit FIFO
64-byte receive FIFO with error flags
Programmable and selectable transmit and receive FIFO trigger levels for DMA and
interrupt generation
Software/hardware flow control
‹ Programmable Xon/Xoff characters
‹ Programmable auto-RTS and auto-CTS
Optional data flow resume by Xon any character
DMA signalling capability for both received and transmitted data
Supports 5 V, 3.3 V and 2.5 V operation
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
„
„
„
„
„
„
„
„
„
„
„
„
„
5 V tolerant on input only pins1
Software selectable baud rate generator
Prescaler provides additional divide-by-4 function
Industrial temperature range (−40 °C to +85 °C)
Fast data bus access time
Programmable Sleep mode
Programmable serial interface characteristics
‹ 5-bit, 6-bit, 7-bit, or 8-bit characters
‹ Even, odd, or no parity bit generation and detection
‹ 1, 1.5, or 2 stop bit generation
False start bit detection
Complete status reporting capabilities in both normal and Sleep mode
Line break generation and detection
Internal test and loopback capabilities
Fully prioritized interrupt system controls
Modem control functions (CTS, RTS, DSR, DTR, RI, and CD)
3. Ordering information
Table 1.
Ordering information
Type number
Package
Name
1.
Description
Version
SC68C752BIB48 LQFP48
plastic low profile quad flat package; 48 leads;
body 7 × 7 × 1.4 mm
SOT313-2
SC68C752BIBS
plastic thermal enhanced very thin quad flat package; SOT617-1
no leads; 32 terminals; body 5 × 5 × 0.85 mm
HVQFN32
For data bus pins D7 to D0, see Table 25 “Limiting values”.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
2 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
4. Block diagram
SC68C752B
TRANSMIT
FIFO
REGISTER
D0 to D7
R/W
RESET
TRANSMIT
SHIFT
REGISTER
TXA, TXB
RECEIVE
SHIFT
REGISTER
RXA, RXB
DATA BUS
AND
CONTROL
LOGIC
A0 to A3
CS
REGISTER
SELECT
LOGIC
INTERCONNECT BUS LINES
AND
CONTROL SIGNALS
FLOW
CONTROL
LOGIC
RECEIVE
FIFO
REGISTER
FLOW
CONTROL
LOGIC
DTRS, DTRB
RTSA, RTSB
OPA, OPB
IRQ
TXRDYA, TXRDYB
RXRDYA, RXRDYB
INTERRUPT
CONTROL
LOGIC
CLOCK AND
BAUD RATE
GENERATOR
MODEM
CONTROL
LOGIC
CTSA, CTSB
RIA, RIB
CDA, CDB
DSRA, DSRB
002aab017
XTAL1
Fig 1.
XTAL2
Block diagram of SC68C752B
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
3 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
5. Pinning information
37 n.c.
38 CTSA
39 DSRA
40 CDA
41 RIA
42 VCC
43 TXRDYA
44 D0
45 D1
46 D2
D5
1
36 RESET
D6
2
35 DTRB
D7
3
34 DTRA
RXB
4
33 RTSA
RXA
5
32 OPA
TXRDYB
6
TXA
7
TXB
8
29 n.c.
OPB
9
28 A0
CS 10
27 A1
A3 11
26 A2
n.c. 12
25 n.c.
31 RXRDYA
GND 24
CTSB 23
RTSB 22
30 IRQ
RIB 21
DSRB 20
VCC 19
RXRDYB 18
GND 17
CDB 16
R/W 15
XTAL2 14
SC68C752BIB48
XTAL1 13
002aab018
25 CTSA
26 VCC
27 D0
28 D1
29 D2
30 D3
32 D5
terminal 1
index area
31 D4
Pin configuration for LQFP48
D6
1
24 RESET
D7
2
23 RTSA
RXB
3
22 OPA
RXA
4
TXA
5
TXB
6
19 A0
OPB
7
18 A1
CS
8
17 A2
21 IRQ
20 n.c.
CTSB 16
RTSB 15
n.c. 14
GND 13
R/W 12
XTAL2 11
A3
9
SC68C752BIBS
XTAL1 10
Fig 2.
47 D3
48 D4
5.1 Pinning
002aac014
Transparent top view
Fig 3.
Pin configuration for HVQFN32
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
4 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
5.2 Pin description
Table 2.
Pin description
Symbol
Pin
Type
Description
I
Address 0 select bit. Internal registers address selection.
LQFP48 HVQFN32
A0
28
19
A1
27
18
I
Address 1 select bit. Internal registers address selection.
A2
26
17
I
Address 2 select bit. Internal registers address selection.
A3
11
9
I
Address 3. A3 is used to select Channel A or Channel B. A logic LOW selects
Channel A, and a logic HIGH selects Channel B. (See Table 3.)
Carrier Detect (active LOW). These inputs are associated with individual UART
Channel A and Channel B. A logic LOW on these pins indicates that a carrier has
been detected by the modem for that channel. The state of these inputs is
reflected in the Modem Status Register (MSR).
CDA
40
-
I
CDB
16
-
I
CS
10
8
I
Chip Select (active LOW). This pin enables data transfers between the user
CPU and the SC68C752B for the channel(s) addressed. Individual UART
sections (A, B) are addressed by A3. See Table 3.
CTSA
38
25
I
CTSB
23
15
I
Clear to Send (active LOW). These inputs are associated with individual UART
Channel A and Channel B. A logic 0 (LOW) on the CTSn pins indicates the
modem or data set is ready to accept transmit data from the SC68C752B. Status
can be tested by reading MSR[4]. These pins only affect the transmit and receive
operations when auto-CTS function is enabled via the Enhanced Feature
Register EFR[7] for hardware flow control operation.
D0
44
27
I/O
D1
45
28
I/O
D2
46
29
I/O
D3
47
30
I/O
D4
48
31
I/O
D5
1
32
I/O
D6
2
1
I/O
D7
3
2
I/O
DSRA
39
-
I
DSRB
20
-
I
DTRA
34
-
O
DTRB
35
-
O
GND
17, 24
13[1]
I
Signal and power ground.
IRQ
30
21
O
Interrupt Request. Interrupts from UART Channel A and Channel B are
wire-ORed internally to function as a single IRQ interrupt. This pin transitions to a
logic 0 (if enabled by the Interrupt Enable Register) whenever a UART channel(s)
requires service. Individual channel interrupt status can be determined by
addressing each channel through its associated internal register, using CS and
A3. An external pull-up resistor must be connected between this pin and VCC.
Data bus (bidirectional). These pins are the 8-bit, 3-state data bus for
transferring information to or from the controlling CPU. D0 is the least significant
bit and the first data bit in a transmit or receive serial data stream.
Data Set Ready (active LOW). These inputs are associated with individual
UART Channel A and Channel B. A logic 0 (LOW) on these pins indicates the
modem or data set is powered-on and is ready for data exchange with the UART.
The state of these inputs is reflected in the Modem Status Register (MSR).
Data Terminal Ready (active LOW). These outputs are associated with
individual UART Channel A and Channel B. A logic 0 (LOW) on these pins
indicates that the SC68C752B is powered-on and ready. These pins can be
controlled via the Modem Control Register. Writing a logic 1 to MCR[0] will set the
DTRn output pin to logic 0 (LOW), enabling the modem. The output of these pins
will be a logic 1 after writing a logic 0 to MCR[0], or after a reset.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
5 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Table 2.
Pin description …continued
Symbol
Pin
Type
Description
LQFP48 HVQFN32
R/W
15
12
I
A logic LOW on this pin will transfer the contents of the data bus (D[7:0]) from an
external CPU to an internal register that is defined by address bits A[2:0]. A logic
HIGH on this pin will load the contents of an internal register defined by address
bits A[2:0] on the SC68C752B data bus (D[7:0]) for access by an external CPU.
n.c.
12, 25,
29, 37
14, 20
-
not connected
User defined outputs. This function is associated with individual Channel A and
Channel B. The state of these pins is defined by the user through the software
settings of MCR[3]. OPA/OPB is a logic 0 when MCR[3] is set to a logic 1.
OPA/OPB is a logic 1 when MCR[3] is set to a logic 0. The output of these two
pins is HIGH after reset.
OPA
32
22
O
OPB
9
7
O
RESET
36
24
I
Reset (active LOW). This pin will reset the internal registers and all the outputs.
The UART transmitter output and the receiver input will be disabled during reset
time. RESET is an active LOW input.
Ring Indicator (active LOW). These inputs are associated with individual UART
Channel A and Channel B. A logic 0 on these pins indicates the modem has
received a ringing signal from the telephone line. A LOW-to-HIGH transition on
these input pins generates a modem status interrupt, if enabled. The state of
these inputs is reflected in the Modem Status Register (MSR).
RIA
41
-
I
RIB
21
-
I
RTSA
33
23
O
RTSB
22
16
O
Request to Send (active LOW). These outputs are associated with individual
UART Channel A and Channel B. A logic 0 on the RTSn pin indicates the
transmitter has data ready and waiting to send. Writing a logic 1 in the Modem
Control Register MCR[1] will set this pin to a logic 0, indicating data is available.
After a reset these pins are set to a logic 1. These pins only affect the transmit
and receive operations when auto-RTS function is enabled via the Enhanced
Feature Register (EFR[6]) for hardware flow control operation.
RXA
5
4
I
RXB
4
3
I
Receive data input. These inputs are associated with individual serial channel
data to the SC68C752B. During the local Loopback mode, these RXn input pins
are disabled and transmit data is connected to the UART receive input internally.
RXRDYA
31
-
O
RXRDYB
18
-
O
TXA
7
5
O
TXB
8
6
O
TXRDYA
43
-
O
TXRDYB
6
-
O
Transmit Ready (active LOW). TXRDYA or TXRDYB go LOW when there are at
least a trigger level number of spaces available or when the FIFO is empty. It
goes HIGH when the FIFO is full or not empty.
VCC
19, 42
26
I
Power supply input.
XTAL1
13
10
I
Crystal or external clock input. Functions as a crystal input or as an external
clock input. A crystal can be connected between XTAL1 and XTAL2 to form an
internal oscillator circuit (see Figure 13). Alternatively, an external clock can be
connected to this pin to provide custom data rates.
XTAL2
14
11
O
Output of the crystal oscillator or buffered clock. (See also XTAL1.) XTAL2 is
used as a crystal oscillator output or a buffered clock output.
Receive Ready (active LOW). RXRDYA or RXRDYB goes LOW when the
trigger level has been reached or the FIFO has at least one character. It goes
HIGH when the receive FIFO is empty.
Transmit data A, B. These outputs are associated with individual serial transmit
channel data from the SC68C752B. During the local Loopback mode, the TXn
output pin is disabled and transmit data is internally connected to the UART
receive input.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
6 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
[1]
HVQFN32 package die supply ground is connected to both GND pin and exposed center pad. GND pin must be connected to supply
ground for proper device operation. For enhanced thermal, electrical, and board level performance, the exposed pad needs to be
soldered to the board using a corresponding thermal pad on the board and for proper heat conduction through the board, thermal vias
need to be incorporated in the PCB in the thermal pad region.
Table 3.
Channel selection using CS pin
CS
A3
UART channel
1
-
none
0
0
channel A
0
1
channel B
6. Functional description
The UART will perform serial-to-parallel conversion on data characters received from
peripheral devices or modems, and parallel-to-parallel conversion on data characters
transmitted by the processor. The complete status of each channel of the SC68C752B
UART can be read at any time during functional operation by the processor.
The SC68C752B can be placed in an alternate mode (FIFO mode) relieving the processor
of excessive software overhead by buffering received/transmitted characters. Both the
receiver and transmitter FIFOs can store up to 64 bytes (including three additional bits of
error status per byte for the receiver FIFO) and have selectable or programmable trigger
levels. Primary outputs RXRDYn and TXRDYn allow signalling of DMA transfers.
The SC68C752B has selectable hardware flow control and software flow control.
Hardware flow control significantly reduces software overhead and increases system
efficiency by automatically controlling serial data flow using the RTSn output and CTSn
input signals. Software flow control automatically controls data flow by using
programmable Xon/Xoff characters.
The UART includes a programmable baud rate generator that can divide the timing
reference clock input by a divisor between 1 and (216 − 1).
6.1 Trigger levels
The SC68C752B provides independent selectable and programmable trigger levels for
both receiver and transmitter DMA and interrupt generation. After reset, both transmitter
and receiver FIFOs are disabled and so, in effect, the trigger level is the default value of
one byte. The selectable trigger levels are available via the FCR. The programmable
trigger levels are available via the Trigger Level Register (TLR).
6.2 Hardware flow control
Hardware flow control is comprised of auto-CTS and auto-RTS. Auto-CTS and auto-RTS
can be enabled/disabled independently by programming EFR[7:6].
With auto-CTS, CTSn must be active before the UART can transmit data.
Auto-RTS only activates the RTSn output when there is enough room in the FIFO to
receive data and de-activates the RTSn output when the receive FIFO is sufficiently full.
The halt and resume trigger levels in the TCR determine the levels at which RTSn is
activated/deactivated.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
7 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
If both auto-CTS and auto-RTS are enabled, when RTSn is connected to CTSn, data
transmission does not occur unless the receive FIFO has empty space. Thus, overrun
errors are eliminated during hardware flow control. If not enabled, overrun errors occur if
the transmit data rate exceeds the receive FIFO servicing latency.
UART 1
UART 2
SERIAL TO
PARALLEL
RXn
PARALLEL
TO SERIAL
TXn
RECEIVE
FIFO
TRANSMIT
FIFO
FLOW
CONTROL
RTSn
CTSn
FLOW
CONTROL
D7 to D0
D7 to D0
PARALLEL
TO SERIAL
TXn
RXn
SERIAL TO
PARALLEL
TRANSMIT
FIFO
RECEIVE
FIFO
FLOW
CONTROL
RTSn
CTSn
FLOW
CONTROL
002aaf090
Fig 4.
Auto flow control (auto-RTS and auto-CTS) example
6.2.1 Auto-RTS
Auto-RTS data flow control originates in the receiver block (see Figure 1 “Block diagram
of SC68C752B” on page 3). Figure 5 shows RTSn functional timing. The receiver FIFO
trigger levels used in auto-RTS are stored in the TCR. RTSn is active if the receiver FIFO
level is below the halt trigger level in TCR[3:0]. When the receiver FIFO halt trigger level is
reached, RTSn is de-asserted. The sending device (for example, another UART) may
send an additional byte after the trigger level is reached (assuming the sending UART has
another byte to send) because it may not recognize the de-assertion of RTSn until it has
begun sending the additional byte. RTSn is automatically reasserted once the receiver
FIFO reaches the resume trigger level programmed via TCR[7:4]. This re-assertion allows
the sending device to resume transmission.
RXn
Start
byte N
Stop
Start
byte N + 1
Stop
Start
RTSn
R/W
1
2
N
N+1
002aab086
N = receiver FIFO trigger level.
The two blocks in dashed lines cover the case where an additional byte is sent, as described in Section 6.2.1.
Fig 5.
RTSn functional timing
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
8 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.2.2 Auto-CTS
The transmitter circuitry checks CTSn before sending the next data byte. When CTSn is
active, the transmitter sends the next byte. To stop the transmitter from sending the
following byte, CTSn must be de-asserted before the middle of the last stop bit that is
currently being sent. The auto-CTS function reduces interrupts to the host system. When
flow control is enabled, CTSn level changes do not trigger host interrupts because the
device automatically controls its own transmitter. Without auto-CTS, the transmitter sends
any data present in the transmit FIFO and a receiver overrun error may result.
TXn
Start
byte 0 to 7
Start
Stop
byte 0 to 7
Stop
CTSn
002aaa227
When CTSn is LOW, the transmitter keeps sending serial data out.
When CTSn goes HIGH before the middle of the last stop bit of the current byte, the transmitter finishes sending the current
byte, but is does not send the next byte.
When CTSn goes from HIGH to LOW, the transmitter begins sending data again.
Fig 6.
CTSn functional timing
6.3 Software flow control
Software flow control is enabled through the Enhanced Feature Register and the Modem
Control Register. Different combinations of software flow control can be enabled by setting
different combinations of EFR[3:0]. Table 4 shows software flow control options.
Table 4.
Software flow control options (EFR[3:0])
EFR[3]
EFR[2]
EFR[1]
EFR[0]
TX, RX software flow controls
0
0
X
X
no transmit flow control
1
0
X
X
transmit Xon1, Xoff1
0
1
X
X
transmit Xon2, Xoff2
1
1
X
X
transmit Xon1, Xon2, Xoff1, Xoff2
X
X
0
0
no receive flow control
X
X
1
0
receiver compared Xon1, Xoff1
X
X
0
1
receiver compares Xon2, Xoff2
1
0
1
1
transmit Xon1, Xoff1
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
0
1
1
1
transmit Xon2, Xoff2
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
1
1
1
1
transmit Xon1, Xon2, Xoff1, Xoff2
receiver compares Xon1 and Xon2, Xoff1 and Xoff2
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
9 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
There are two other enhanced features relating to software flow control:
• Xon Any function (MCR[5]): Operation will resume after receiving any character
after recognizing the Xoff character. It is possible that an Xon1 character is
recognized as an Xon Any character, which could cause an Xon2 character to be
written to the RX FIFO.
• Special character (EFR[5]): Incoming data is compared to Xoff2. Detection of the
special character sets the Xoff interrupt (IIR[4]) but does not halt transmission. The
Xoff interrupt is cleared by a read of the IIR. The special character is transferred to the
RX FIFO.
6.3.1 Receive flow control
When software flow control operation is enabled, the SC68C752B will compare incoming
data with Xoff1/Xoff2 programmed characters (in certain cases, Xoff1 and Xoff2 must be
received sequentially). When the correct Xoff character are received, transmission is
halted after completing transmission of the current character. Xoff detection also sets
IIR[4] (if enabled via IER[5]) and causes IRQ to go HIGH.
To resume transmission, an Xon1/Xon2 character must be received (in certain cases
Xon1 and Xon2 must be received sequentially). When the correct Xon characters are
received, IIR[4] is cleared, and the Xoff interrupt disappears.
6.3.2 Transmit flow control
Xoff1/Xoff2 character is transmitted when the RX FIFO has passed the HALT trigger level
programmed in TCR[3:0].
Xon1/Xon2 character is transmitted when the RX FIFO reaches the RESUME trigger level
programmed in TCR[7:4].
The transmission of Xoff/Xon(s) follows the exact same protocol as transmission of an
ordinary byte from the FIFO. This means that even if the word length is set to be 5, 6, or 7
characters, then the 5, 6, or 7 least significant bits of Xoff1/Xoff2, Xon1/Xon2 will be
transmitted. (Note that the transmission of 5, 6, or 7 bits of a character is seldom done, but
this functionality is included to maintain compatibility with earlier designs.)
It is assumed that software flow control and hardware flow control will never be enabled
simultaneously. Figure 7 shows an example of software flow control.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
10 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.3.3 Software flow control example
UART1
UART2
TRANSMIT FIFO
PARALLEL-TO-SERIAL
RECEIVE FIFO
data
SERIAL-TO-PARALLEL
Xoff–Xon–Xoff
SERIAL-TO-PARALLEL
PARALLEL-TO-SERIAL
Xon1 WORD
Xon1 WORD
Xon2 WORD
Xon2 WORD
Xoff1 WORD
Xoff1 WORD
Xoff2 WORD
Fig 7.
6.3.3.1
compare
programmed
Xon-Xoff
characters
Xoff2 WORD
002aaa229
Software flow control example
Assumptions
UART1 is transmitting a large text file to UART2. Both UARTs are using software flow
control with single character Xoff (0F) and Xon (0D) tokens. Both have Xoff threshold
(TCR[3:0] = F) set to 60, and Xon threshold (TCR[7:4] = 8) set to 32. Both have the
interrupt receive threshold (TLR[7:4] = D) set to 52.
UART1 begins transmission and sends 52 characters, at which point UART2 will generate
an interrupt to its processor to service the RX FIFO, but assume the interrupt latency is
fairly long. UART1 will continue sending characters until a total of 60 characters have
been sent. At this time, UART2 will transmit a 0Fh to UART1, informing UART1 to halt
transmission. UART1 will likely send the 61st character while UART2 is sending the Xoff
character. Now UART2 is serviced and the processor reads enough data out of the RX
FIFO that the level drops to 32. UART2 will now send a 0Dh to UART1, informing UART1
to resume transmission.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
11 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.4 Reset
Table 5 summarizes the state of register after reset.
Table 5.
Register reset functions
Register
Reset control
Reset state
Interrupt Enable Register
RESET
all bits cleared
Interrupt Identification Register
RESET
bit 0 is set; all other bits cleared
FIFO Control Register
RESET
all bits cleared
Line Control Register
RESET
reset to 0001 1101 (1Dh)
Modem Control Register
RESET
all bits cleared
Line Status Register
RESET
bits 5 and 6 set; all other bits cleared
Modem Status Register
RESET
bits 0 to 3 cleared; bits 4 to 7 input signals
Enhanced Feature Register
RESET
all bits cleared
Receiver Holding Register
RESET
pointer logic cleared
Transmitter Holding Register
RESET
pointer logic cleared
Transmission Control Register
RESET
all bits cleared
Trigger Level Register
RESET
all bits cleared
Remark: Registers DLL, DLM, SPR, XON1, XON2, XOFF1, XOFF2 are not reset by the
top-level reset signal RESET, that is, they hold their initialization values during reset.
Table 6 summarizes the state of registers after reset.
Table 6.
Signal RESET functions
Signal
Reset control
Reset state
TXn
RESET
HIGH
RTSn
RESET
HIGH
DTRn
RESET
HIGH
RXRDYn
RESET
HIGH
TXRDYn
RESET
LOW
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Product data sheet
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.5 Interrupts
The SC68C752B has interrupt generation and prioritization (six prioritized levels of
interrupts) capability. The Interrupt Enable Register (IER) enables each of the six types of
interrupts and the IRQ signal in response to an interrupt generation. The IER can also
disable the interrupt system by clearing bits 3:0 and bits 7:5. When an interrupt is
generated, the IIR indicates that an interrupt is pending and provides the type of interrupt
through IIR[5:0]. Table 7 summarizes the interrupt control functions.
Table 7.
Interrupt control functions
IIR[5:0]
Priority Interrupt type
level
Interrupt source
Interrupt reset method
000001
None
none
none
none
000110
1
receiver line
status
OE, FE, PE, or BI errors occur
in characters in the RX FIFO
FE, PE, BI: all erroneous
characters are read from
the RX FIFO.
001100
2
RX time-out
stale data in RX FIFO
read RHR
000100
2
RHR interrupt
DRDY (data ready)
read RHR
OE: read LSR
(FIFO disable)
RX FIFO above trigger level
(FIFO enable)
000010
3
THR interrupt
TFE (THR empty)
(FIFO disable)
read IIR or a write to the
THR
TX FIFO passes above trigger
level
(FIFO enable)
000000
4
modem status
MSR[3:0] = 0
read MSR
010000
5
Xoff interrupt
receive Xoff character(s)/
special character
receive Xon character(s)/
Read of IIR
100000
6
CTS, RTS
RTSn pin or CTSn pin change
state from active (LOW) to
inactive (HIGH)
read IIR
It is important to note that for the framing error, parity error, and break conditions, LSR[7]
generates the interrupt. LSR[7] is set when there is an error anywhere in the RX FIFO,
and is cleared only when there are no more errors remaining in the FIFO. LSR[4:2] always
represent the error status for the received character at the top of the RX FIFO. Reading
the RX FIFO updates LSR[4:2] to the appropriate status for the new character at the top of
the FIFO. If the RX FIFO is empty, then LSR[4:2] are all zeros.
For the Xoff interrupt, if an Xoff flow character detection caused the interrupt, the interrupt
is cleared by an Xon flow character detection. If a special character detection caused the
interrupt, the interrupt is cleared by a read of the IIR.
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.5.1 Interrupt mode operation
In Interrupt mode (if any bit of IER[3:0] is 1) the processor is informed of the status of the
receiver and transmitter by an interrupt signal, IRQ. Therefore, it is not necessary to
continuously poll the Line Status Register (LSR) to see if any interrupt needs to be
serviced. Figure 8 shows Interrupt mode operation.
IIR
R/W
IRQ
PROCESSOR
IER
1
1
THR
1
1
RHR
002aab096
Fig 8.
Interrupt mode operation
6.5.2 Polled mode operation
In Polled mode (IER[3:0] = 0000) the status of the receiver and transmitter can be
checked by polling the Line Status Register (LSR). This mode is an alternative to the FIFO
Interrupt mode of operation where the status of the receiver and transmitter is
automatically known by means of interrupts sent to the CPU. Figure 9 shows FIFO
polled mode operation.
IIR
R/W
PROCESSOR
IER
0
THR
0
0
0
RHR
002aab097
Fig 9.
FIFO polled mode operation
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.6 DMA operation
There are two modes of DMA operation, DMA mode 0 or DMA mode 1, selected by
FCR[3].
In DMA mode 0 or FIFO disable (FCR[0] = 0) DMA occurs in single character transfers. In
DMA mode 1, multi-character (or block) DMA transfers are managed to relieve the
processor for longer periods of time.
6.6.1 Single DMA transfers (DMA mode 0/FIFO disable)
Figure 10 shows TXRDYn and RXRDYn in DMA mode 0/FIFO disable.
transmit
receive
TXRDYn
at least one
location filled
wrptr
RXRDYn
at least one
location filled
rdptr
RXRDYn
TXRDYn
wrptr
FIFO EMPTY
rdptr
FIFO EMPTY
002aaa232
Fig 10. TXRDYn and RXRDYn in DMA mode 0/FIFO disable
6.6.1.1
Transmitter
When empty, the TXRDYn signal becomes active. TXRDYn will go inactive after one
character has been loaded into it.
6.6.1.2
Receiver
RXRDYn is active when there is at least one character in the FIFO. It becomes inactive
when the receiver is empty.
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.6.2 Block DMA transfers (DMA mode 1)
Figure 11 shows TXRDYn and RXRDYn in DMA mode 1.
wrptr
transmit
receive
trigger
level
TXRDYn
RXRDYn
rdptr
at least one
location filled
FIFO full
trigger
level
wrptr
TXRDYn
RXRDYn
rdptr
FIFO EMPTY
002aaa234
Fig 11. TXRDYn and RXRDYn in DMA mode 1
6.6.2.1
Transmitter
TXRDYn is active when there is a trigger level number of spaces available. It becomes
inactive when the FIFO is full.
6.6.2.2
Receiver
RXRDYn becomes active when the trigger level has been reached, or when a time-out
interrupt occurs. It will go inactive when the FIFO is empty or an error in the receive FIFO
is flagged by LSR[7].
6.7 Sleep mode
Sleep mode is an enhanced feature of the SC68C752B UART. It is enabled when EFR[4],
the enhanced functions bit, is set and when IER[4] is set. Sleep mode is entered when:
• The serial data input line, RXn, is idle (see Section 6.8 “Break and time-out
conditions”).
• The transmit FIFO and transmit shift register are empty.
• There are no interrupts pending except THR and time-out interrupts.
Remark: Sleep mode will not be entered if there is data in the receive FIFO.
In Sleep mode, the UART clock and baud rate clock are stopped. Since most registers are
clocked using these clocks, the power consumption is greatly reduced. The UART will
wake up when any change is detected on the RXn line, when there is any change in the
state of the modem input pins, or if data is written to the transmit FIFO.
Remark: Writing to the divisor latches, DLL and DLM, to set the baud clock, must not be
done during Sleep mode. Therefore, it is advisable to disable Sleep mode using IER[4]
before writing to DLL or DLM.
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Product data sheet
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
6.8 Break and time-out conditions
An RX idle condition is detected when the receiver line, RXn, has been HIGH for
4 character time. The receiver line is sampled midway through each bit.
When a break condition occurs, the TXn line is pulled LOW. A break condition is activated
by setting LCR[6].
6.9 Programmable baud rate generator
The SC68C752B UART contains a programmable baud generator that takes any clock
input and divides it by a divisor in the range between 1 and (216 − 1). An additional
divide-by-4 prescaler is also available and can be selected by MCR[7], as shown in
Figure 12. The output frequency of the baud rate generator is 16 times the baud rate. The
formula for the divisor is:
XTAL1 crystal input frequency⎞
⎛ ----------------------------------------------------------------------------------⎝
⎠
prescaler
divisor = ----------------------------------------------------------------------------------------desired baud rate × 16
(1)
Where:
prescaler = 1, when MCR[7] is set to 0 after reset (divide-by-1 clock selected)
prescaler = 4, when MCR[7] is set to 1 after reset (divide-by-4 clock selected).
Remark: The default value of prescaler after reset is divide-by-1.
Figure 12 shows the internal prescaler and baud rate generator circuitry.
PRESCALER
LOGIC
(DIVIDE-BY-1)
XTAL1
XTAL2
INTERNAL
OSCILLATOR
LOGIC
MCR[7] = 0
input clock
PRESCALER
LOGIC
(DIVIDE-BY-4)
reference
clock
BAUD RATE
GENERATOR
LOGIC
internal
baud rate
clock for
transmitter
and receiver
MCR[7] = 1
002aaa233
Fig 12. Prescaler and baud rate generator block diagram
DLL and DLM must be written to in order to program the baud rate. DLL and DLM are the
least significant and most significant byte of the baud rate divisor. If DLL and DLM are
both zero, the UART is effectively disabled, as no baud clock will be generated.
Remark: The programmable baud rate generator is provided to select both the transmit
and receive clock rates.
Table 8 and Table 9 show the baud rate and divisor correlation for crystal with frequency
1.8432 MHz and 3.072 MHz, respectively.
Figure 13 shows the crystal clock circuit reference.
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Product data sheet
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Table 8.
Baud rates using a 1.8432 MHz crystal
Desired baud rate
Divisor used to generate
16× clock
50
2304
75
1536
110
1047
0.026
134.5
857
0.058
150
768
300
384
600
192
1200
96
1800
64
2000
58
2400
48
3600
32
4800
24
7200
16
9600
12
19200
6
38400
3
56000
2
Table 9.
0.69
2.86
Baud rates using a 3.072 MHz crystal
Desired baud rate
Divisor used to generate
16× clock
50
2304
75
2560
110
1745
0.026
134.5
1428
0.034
150
1280
300
640
600
320
1200
160
1800
107
2000
96
2400
80
3600
53
4800
40
7200
27
9600
20
19200
10
38400
5
SC68C752B_4
Product data sheet
Percent error difference
between desired and actual
Percent error difference
between desired and actual
0.312
0.628
1.23
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Rev. 04 — 20 January 2010
18 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
XTAL1
XTAL2
XTAL1
X1
1.8432 MHz
C1
22 pF
XTAL2
X1
1.8432 MHz
C2
33 pF
C1
22 pF
1.5 kΩ
C2
47 pF
002aaa870
Fig 13. Crystal oscillator connections
7. Register descriptions
Each register is selected using address lines A0, A1, A2, and in some cases, bits from
other registers. The programming combinations for register selection are shown in
Table 10.
Table 10.
Register map - read/write properties
A2
A1
A0
Read mode
Write mode
0
0
0
Receive Holding Register (RHR)
Transmit Holding Register (THR)
0
0
1
Interrupt Enable Register (IER)
Interrupt Enable Register
0
1
0
Interrupt Identification Register (IIR)
FIFO Control Register (FCR)
0
1
1
Line Control Register (LCR)
Line Control Register
1
0
0
Modem Control Register
(MCR)[1]
1
0
1
Line Status Register (LSR)
1
1
0
Modem Status Register (MSR)
1
1
1
ScratchPad Register (SPR)
ScratchPad Register
(DLL)[2][3]
divisor latch LSB[2][3]
0
0
0
Divisor Latch LSB
0
0
1
Divisor Latch MSB (DLM)[2][3]
divisor latch MSB[2][3]
0
1
0
Enhanced Feature Register (EFR)[2][4]
Enhanced Feature Register[2][4]
word[2][4]
Xon1 word[2][4]
1
0
0
Xon1
1
0
1
Xon2 word[2][4]
Xon2 word[2][4]
1
1
0
Xoff1 word[2][4]
Xoff1 word[2][4]
1
1
1
Xoff2 word[2][4]
Xoff2 word[2][4]
(TCR)[2][5]
1
1
0
Transmission Control Register
1
1
1
Trigger Level Register (TLR)[2][5]
1
1
1
FIFO ready register[2][6]
Transmission Control Register[2][5]
Trigger Level Register[2][5]
[1]
MCR[7] can only be modified when EFR[4] is set.
[2]
Accessed by a combination of address pins and register bits.
[3]
Accessible only when LCR[7] is logic 1.
[4]
Accessible only when LCR is set to 1011 1111 (BFh).
[5]
Accessible only when EFR[4] = 1 and MCR[6] = 1, that is, EFR[4] and MCR[6] are read/write enables.
[6]
Accessible only when CS = 0, MCR[2] = 1, and loopback is disabled (MCR[4] = 0).
SC68C752B_4
Product data sheet
Modem Control Register[1]
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Table 11 lists and describes the SC68C752B internal registers.
Table 11.
SC68C752B internal registers
A2 A1 A0 Register
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Read/
Write
General register set[1]
0
0
0
RHR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R
0
0
0
THR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
W
RTS
interrupt
enable[2]
Xoff[2]
Sleep
mode[2]
modem
status
interrupt
receive
THR
line status empty
interrupt
interrupt
0
0
1
IER
CTS
interrupt
enable[2]
0
1
0
FCR
RX trigger RX trigger TX trigger TX trigger DMA
level
level
level
level
mode
(MSB)
(LSB)
(MSB)[2] (LSB)[2]
select
0
1
0
IIR
FCR[0]
FCR[0]
0
1
1
LCR
DLAB
break
set parity parity
control bit
type
select
1
0
0
MCR
1× or 1×/4 TCR and
clock[2]
TLR
enable[2]
Xon
Any[2]
1
0
1
LSR
error in
RX FIFO
THR and
TSR
empty
1
1
0
MSR
CD
1
1
1
SPR
1
1
0
1
1
1
1
1
1
FIFO Rdy 0
RX data R/W
available
interrupt
TX FIFO
reset
RX FIFO FIFO
reset
enable
W
interrupt
priority
bit 2
interrupt
priority
bit 1
interrupt
priority
bit 0
interrupt
status
R
parity
enable
number of word
stop bits length
bit 1
word
length
bit 0
R/W
enable
loopback
OPA/
OPB
control
FIFO
ready
enable
RTS
DTR
R/W
THR
empty
break
interrupt
framing
error
parity
error
overrun
error
data in
receiver
R
RI
DSR
CTS
ΔCD
ΔRI
ΔDSR
ΔCTS
R
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
TCR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
TLR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
0
RX FIFO
B status
RX FIFO
A status
0
0
TX FIFO TX FIFO
B status A status
CTS,
RTS
Xoff
R
Special register set[3]
0
0
0
DLL
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
0
0
1
DLM
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
bit 9
bit 8
R/W
Enhanced register set[4]
0
1
0
EFR
auto-CTS auto-RTS special
enable
software
character enhanced flow
detect
functions control
[2]
bit 3
software
flow
control
bit 2
software
flow
control
bit 1
software
flow
control
bit 0
R/W
1
0
0
XON1
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
0
1
XON2
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
1
0
XOFF1
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
1
1
XOFF2
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
[1]
These registers are accessible only when LCR[7] = 0.
[2]
This bit can only be modified if register bit EFR[4] is enabled, that is, if enhanced functions are enabled.
[3]
The Special register set is accessible only when LCR[7] is set to a logic 1.
[4]
Enhanced Feature Register; XON1/XON2 and XOFF1/XOFF2 are accessible only when LCR is set to ‘BFh’.
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Remark: Refer to the notes under Table 10 for more register access information.
7.1 Receiver Holding Register (RHR)
The receiver section consists of the Receiver Holding Register (RHR) and the Receiver
Shift Register (RSR). The RHR is actually a 64-byte FIFO. The RSR receives serial data
from the RX terminal. The data is converted to parallel data and moved to the RHR. The
receiver section is controlled by the line control register. If the FIFO is disabled, location
zero of the FIFO is used to store the characters.
Remark: In this case, characters are overwritten if overflow occurs.
If overflow occurs, characters are lost. The RHR also stores the error status bits
associated with each character.
7.2 Transmit Holding Register (THR)
The transmitter section consists of the Transmit Holding Register (THR) and the Transmit
Shift Register (TSR). The THR is actually a 64-byte FIFO. The THR receives data and
shifts it into the TSR, where it is converted to serial data and moved out on the TX
terminal. If the FIFO is disabled, the FIFO is still used to store the byte. Characters are
lost if overflow occurs.
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.3 FIFO Control Register (FCR)
This is a write-only register that is used for enabling the FIFOs, clearing the FIFOs, setting
transmitter and receiver trigger levels, and selecting the type of DMA signalling. Table 12
shows FIFO Control Register bit settings.
Table 12.
FIFO Control Register bits description
Bit
Symbol
Description
7:6
FCR[7] (MSB), RX trigger. Sets the trigger level for the receive FIFO.
FCR[6] (LSB)
00 - 8 characters
01 - 16 characters
10 - 56 characters
11 - 60 characters
5:4
FCR[5] (MSB), TX trigger. Sets the trigger level for the transmit FIFO.
FCR[4] (LSB)
00 - 8 spaces
01 - 16 spaces
10 - 32 spaces
11 - 56 spaces
FCR[5:4] can only be modified and enabled when EFR[4] is set. This is
because the transmit trigger level is regarded as an enhanced function.
3
FCR[3]
DMA mode select.
logic 0 = Set DMA mode ‘0’
logic 1 = Set DMA mode ‘1’
2
FCR[2]
Reset transmit FIFO.
logic 0 = No FIFO transmit reset (normal default condition)
logic 1 = Clears the contents of the transmit FIFO and resets the FIFO
counter logic (the transmit shift register is not cleared or altered). This
bit will return to a logic 0 after clearing the FIFO.
1
FCR[1]
Reset receive FIFO.
logic 0 = no FIFO receive reset (normal default condition)
logic 1 = Clears the contents of the receive FIFO and resets the FIFO
counter logic (the receive shift register is not cleared or altered). This
bit will return to a logic 0 after clearing the FIFO.
0
FCR[0]
FIFO enable.
logic 0 = disable the transmit and receive FIFO (normal default
condition)
logic 1 = enable the transmit and receive FIFO
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.4 Line Control Register (LCR)
This register controls the data communication format. The word length, number of stop
bits, and parity type are selected by writing the appropriate bits to the LCR. Table 13
shows the Line Control Register bit settings.
Table 13.
Line Control Register bits description
Bit
Symbol
Description
7
LCR[7]
Divisor latch enable.
logic 0 = divisor latch disabled (normal default condition)
logic 1 = divisor latch enabled
6
LCR[6]
Break control bit. When enabled, the Break control bit causes a break
condition to be transmitted (the TXn output is forced to a logic 0 state). This
condition exists until disabled by setting LCR[6] to a logic 0.
logic 0 = no break condition (normal default condition)
logic 1 = forces the transmitter output (TXn) to a logic 0 to alert the
communication terminal to a line break condition
5
LCR[5]
Set parity. LCR[5] selects the forced parity format (if LCR[3] = 1).
logic 0 = parity is not forced (normal default condition)
LCR[5] = logic 1 and LCR[4] = logic 0: parity bit is forced to a logic 1 for the
transmit and receive data.
LCR[5] = logic 1 and LCR[4] = logic 1: parity bit is forced to a logic 0 for the
transmit and receive data.
4
LCR[4]
Parity type select.
logic 0 = odd parity is generated (if LCR[3] = 1).
logic 1 = even parity is generated (if LCR[3] = 1).
3
LCR[3]
Parity enable.
logic 0 = no parity (normal default condition).
logic 1 = a parity bit is generated during transmission and the receiver
checks for received parity.
2
LCR[2]
Number of stop bits. Specifies the number of stop bits.
0 = 1 stop bit (word length = 5, 6, 7, 8)
1 = 1.5 stop bits (word length = 5)
1 = 2 stop bits (word length = 6, 7, 8)
1:0
LCR[1:0]
Word length bits 1, 0. These two bits specify the word length to be
transmitted or received.
00 = 5 bits
01 = 6 bits
10 = 7 bits
11 = 8 bits
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NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.5 Line Status Register (LSR)
Table 14 shows the Line Status Register bit settings.
Table 14.
Line Status Register bits description
Bit
Symbol
Description
7
LSR[7]
FIFO data error.
logic 0 = No error (normal default condition)
logic 1 = At least one parity error, framing error, or break indication is in the
receiver FIFO. This bit is cleared when no more errors are present in the
FIFO.
6
LSR[6]
THR and TSR empty. This bit is the Transmit Empty indicator.
logic 0 = transmitter hold and shift registers are not empty
logic 1 = transmitter hold and shift registers are empty
5
LSR[5]
THR empty. This bit is the Transmit Holding Register Empty indicator.
logic 0 = Transmit Hold Register is not empty
logic 1 = Transmit Hold Register is empty. The processor can now load up to
64 bytes of data into the THR if the TX FIFO is enabled.
4
LSR[4]
Break interrupt.
logic 0 = no break condition (normal default condition)
logic 1 = A break condition occurred and associated byte is 00, that is,
RXn was LOW for one character time frame.
3
LSR[3]
Framing error.
logic 0 = no framing error in data being read from receive FIFO (normal
default condition)
logic 1 = Framing error occurred in data being read from receive FIFO,
that is, received data did not have a valid stop bit.
2
LSR[2]
Parity error.
logic 0 = no parity error (normal default condition)
logic 1 = parity error in data being read from receive FIFO
1
LSR[1]
Overrun error.
logic 0 = no overrun error (normal default condition)
logic 1 = overrun error has occurred
0
LSR[0]
Data in receiver.
logic 0 = no data in receive FIFO (normal default condition)
logic 1 = at least one character in the receive FIFO
When the LSR is read, LSR[4:2] reflect the error bits (BI, FE, PE) of the character at the
top of the receive FIFO (next character to be read). The LSR[4:2] registers do not
physically exist, as the data read from the receive FIFO is output directly onto the output
data bus, D[4:2], when the LSR is read. Therefore, errors in a character are identified by
reading the LSR and then reading the RHR.
LSR[7] is set when there is an error anywhere in the receive FIFO, and is cleared only
when there are no more errors remaining in the FIFO.
Reading the LSR does not cause an increment of the receive FIFO read pointer. The
receive FIFO read pointer is incremented by reading the RHR.
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
24 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Remark: The three error bits (parity, framing, break) may not be updated correctly in the
first read of the LSR when the input clock (XTAL1) is running faster than 36 MHz.
However, the second read is always correct. It is strongly recommended that when using
this device with a clock faster than 36 MHz, that the LSR be read twice and only the
second read be used for decision making. All other bits in the LSR are correct on all
reads.
7.6 Modem Control Register (MCR)
The MCR controls the interface with the mode, data set, or peripheral device that is
emulating the modem. Table 15 shows Modem Control Register bit settings.
Table 15.
Bit
7
Modem Control Register bits description
Symbol
MCR[7]
Description
[1]
Clock select.
logic 0 = divide-by-1 clock input
logic 1 = divide-by-4 clock input
6
MCR[6]
[1]
TCR and TLR enable.
logic 0 = no action.
logic 1 = enable access to the TCR and TLR registers
5
MCR[5]
[1]
Xon Any.
logic 0 = disable Xon Any function
logic 1 = enable Xon Any function
4
MCR[4]
Enable loopback.
logic 0 = normal operating mode
logic 1 = Enable local Loopback mode (internal). In this mode the
MCR[3:0] signals are looped back into MSR[7:4] and the TXn output is
looped back to the RXn input internally.
3
MCR[3]
OPA/OPB control.
logic 0 = forces OPA/OPB output to HIGH state
logic 1 = forces OPA/OPB output to LOW state. In Loopback mode,
controls MSR[7].
2
MCR[2]
FIFO Ready enable.
logic 0 = Disable the FIFO Rdy register
logic 1 = Enable the FIFO Rdy register. In Loopback mode, controls
MSR[6].
1
MCR[1]
RTS
logic 0 = force RTSn output to inactive (HIGH)
logic 1 = force RTSn output to active (LOW). In Loopback mode,
controls MSR[4]. If auto-RTS is enabled, the RTSn output is controlled
by hardware flow control.
0
MCR[0]
DTR
logic 0 = force DTRn output to inactive (HIGH)
logic 1 = force DTRn output to active (LOW). In Loopback mode,
controls MSR[5].
[1]
MCR[7:5] can only be modified when EFR[4] is set, that is, EFR[4] is a write enable.
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.7 Modem Status Register (MSR)
This 8-bit register provides information about the current state of the control lines from the
mode, data set, or peripheral device to the processor. It also indicates when a control
input from the modem changes state. Table 16 shows Modem Status Register bit settings
per channel.
Table 16.
Modem Status Register bits description
Bit
Symbol
Description
7
MSR[7][1]
CD (active HIGH, logic 1). This bit is the complement of the CDn input during
normal mode. During internal Loopback mode, it is equivalent to the state of
MCR[3].
6
MSR[6][1]
RI (active HIGH, logic 1). This bit is the complement of the RIn input during
normal mode. During internal Loopback mode, it is equivalent to the state of
MCR[2].
5
MSR[5][1]
DSR (active HIGH, logic 1). This bit is the complement of the DSRn input
during normal mode. During internal Loopback mode, it is equivalent to the
state of MCR[0].
4
MSR[4][1]
CTS (active HIGH, logic 1). This bit is the complement of the CTSn input
during normal mode. During internal Loopback mode, it is equivalent to the
state of MCR[1].
3
MSR[3]
ΔCD. Indicates that CDn input (or MCR[3] in Loopback mode) has changed
state. Cleared on a read.
2
MSR[2]
ΔRI. Indicates that RIn input (or MCR[2] in Loopback mode) has changed
state from LOW to HIGH. Cleared on a read.
1
MSR[1]
ΔDSR. Indicates that DSRn input (or MCR[0] in Loopback mode) has changed
state. Cleared on a read.
0
MSR[0]
ΔCTS. Indicates that CTSn input (or MCR[1] in Loopback mode) has changed
state. Cleared on a read.
[1]
The primary inputs RIn, CDn, CTSn, DSRn are all active LOW, but their registered equivalents in the MSR
and MCR (in Loopback mode) registers are active HIGH.
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26 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.8 Interrupt Enable Register (IER)
The Interrupt Enable Register (IER) enables each of the six types of interrupt, receiver
error, RHR interrupt, THR interrupt, Xoff received, or CTSn/RTSn change of state from
LOW to HIGH. The IRQ output signal is activated in response to interrupt generation.
Table 17 shows Interrupt Enable Register bit settings.
Table 17.
Interrupt Enable Register bits description
Bit
Symbol
Description
7
IER[7][1]
CTS interrupt enable.
logic 0 = disable the CTS interrupt (normal default condition)
logic 1 = enable the CTS interrupt
6
IER[6][1]
RTS interrupt enable.
logic 0 = disable the RTS interrupt (normal default condition)
logic 1 = enable the RTS interrupt
5
IER[5][1]
Xoff interrupt.
logic 0 = disable the Xoff interrupt (normal default condition)
logic 1 = enable the Xoff interrupt
4
IER[4][1]
Sleep mode.
logic 0 = disable Sleep mode (normal default condition)
logic 1 = enable Sleep mode. See Section 6.7 “Sleep mode” for details.
3
IER[3]
Modem Status Interrupt.
logic 0 = disable the Modem Status Register interrupt (normal default
condition)
logic 1 = enable the Modem Status Register interrupt
2
IER[2]
Receive Line Status interrupt.
logic 0 = disable the receiver line status interrupt (normal default condition)
logic 1 = enable the receiver line status interrupt
1
IER[1]
Transmit Holding Register interrupt.
logic 0 = disable the THR interrupt (normal default condition)
logic 1 = enable the THR interrupt
0
IER[0]
Receive Holding Register interrupt.
logic 0 = disable the RHR interrupt (normal default condition)
logic 1 = enable the RHR interrupt
[1]
IER[7:4] can only be modified if EFR[4] is set, that is, EFR[4] is a write enable. Re-enabling IER[1] will not
cause a new interrupt if the THR is below the threshold.
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Rev. 04 — 20 January 2010
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.9 Interrupt Identification Register (IIR)
The IIR is a read-only 8-bit register which provides the source of the interrupt in a
prioritized manner. Table 18 shows Interrupt Identification Register bit settings.
Table 18.
Bit
Interrupt Identification Register bits description
Symbol
Description
7:6
IIR[7:6]
Mirror the contents of FCR[0].
5
IIR[5]
RTSn/CTSn LOW-to-HIGH change of state
4
IIR[4]
1 = Xoff/Special character has been detected
3:1
IIR[3:1]
3-bit encoded interrupt. See Table 19.
0
IIR[0]
Interrupt status.
logic 0 = an interrupt is pending
logic 1 = no interrupt is pending
The interrupt priority list is shown in Table 19.
Table 19.
Interrupt priority list
Priority
level
IIR[5]
IIR[4]
IIR[3]
IIR[2]
IIR[1]
IIR[0]
Source of the interrupt
1
0
0
0
1
1
0
receiver line status error
2
0
0
1
1
0
0
receiver time-out interrupt
2
0
0
0
1
0
0
RHR interrupt
3
0
0
0
0
1
0
THR interrupt
4
0
0
0
0
0
0
modem interrupt
5
0
1
0
0
0
0
received Xoff signal/ special
character
6
1
0
0
0
0
0
CTSn, RTSn change of state from
active (LOW) to inactive (HIGH)
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SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
7.10 Enhanced Feature Register (EFR)
This 8-bit register enables or disables the enhanced features of the UART. Table 20
shows the Enhanced Feature Register bit settings.
Table 20.
Enhanced Feature Register bits description
Bit
Symbol
Description
7
EFR[7]
CTS flow control enable.
logic 0 = CTS flow control is disabled (normal default condition)
logic 1 = CTS flow control is enabled. Transmission will stop when a HIGH
signal is detected on the CTSn pin.
6
EFR[6]
RTS flow control enable.
logic 0 = RTS flow control is disabled (normal default condition)
logic 1 = RTS flow control is enabled. The RTSn pin goes HIGH when the
receiver FIFO halt trigger level TCR[3:0] is reached, and goes LOW when the
receiver FIFO resume transmission trigger level TCR[7:4] is reached.
5
EFR[5]
Special character detect.
logic 0 = special character detect disabled (normal default condition)
logic 1 = special character detect enabled. Received data is compared with
Xoff2 data. If a match occurs, the received data is transferred to FIFO and
IIR[4] is set to a logic 1 to indicate a special character has been detected.
4
EFR[4]
Enhanced functions enable bit.
logic 0 = disables enhanced functions and writing to IER[7:4], FCR[5:4],
MCR[7:5]
logic 1 = enables the enhanced function IER[7:4], FCR[5:4], and MCR[7:5]
can be modified, that is, this bit is therefore a write enable
3:0
EFR[3:0]
Combinations of software flow control can be selected by programming these
bits. See Table 4 “Software flow control options (EFR[3:0])” on page 9.
7.11 Divisor latches (DLL, DLM)
These are two 8-bit registers which store the 16-bit divisor for generation of the baud clock
in the baud rate generator. DLM stores the most significant part of the divisor. DLL stores
the least significant part of the divisor.
Note that DLL and DLM can only be written to before Sleep mode is enabled, that is,
before IER[4] is set.
7.12 Transmission Control Register (TCR)
This 8-bit register is used to store the receive FIFO threshold levels to stop/start
transmission during hardware/software flow control. Table 21 shows transmission control
register bit settings.
Table 21.
Transmission Control Register bits description
Bit
Symbol
Description
7:4
TCR[7:4]
receive FIFO trigger level to resume transmission (0 bytes to 60 bytes).
3:0
TCR[3:0]
receive FIFO trigger level to halt transmission (0 bytes to 60 bytes).
TCR trigger levels are available from 0 bytes to 60 bytes with a granularity of four.
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29 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Remark: TCR can only be written to when EFR[4] = 1 and MCR[6] = 1. The programmer
must program the TCR such that TCR[3:0] > TCR[7:4]. There is no built-in hardware
check to make sure this condition is met. Also, the TCR must be programmed with this
condition before auto-RTS or software flow control is enabled to avoid spurious operation
of the device.
7.13 Trigger Level Register (TLR)
This 8-bit register is pulsed to store the transmit and received FIFO trigger levels used for
DMA and interrupt generation. Trigger levels from 4 to 60 can be programmed with a
granularity of 4. Table 22 shows trigger level register bit settings.
Table 22.
Trigger Level Register bits description
Bit
Symbol
Description
7:4
TLR[7:4]
receive FIFO trigger levels (4 to 60), number of characters available.
3:0
TLR[3:0]
transmit FIFO trigger levels (4 to 60), number of spaces available.
Remark: TLR can only be written to when EFR[4] = 1 and MCR[6] = 1. If TLR[3:0] or
TLR[7:4] are logic 0, the selectable trigger levels via the FIFO control register (FCR) are
used for the transmit and receive FIFO trigger levels. Trigger levels from
4 bytes to 60 bytes are available with a granularity of four. The TLR should be
programmed for N⁄4, where N is the desired trigger level.
When the trigger level setting in TLR is zero, the SC68C752B uses the trigger level setting
defined in FCR. If TLR has non-zero trigger level value, the trigger level defined in FCR is
discarded. This applies to both transmit FIFO and receive FIFO trigger level setting.
When TLR is used for RX trigger level control, FCR[7:6] should be left at the default state,
that is, ‘00’.
7.14 FIFO ready register
The FIFO ready register provides real-time status of the transmit and receive FIFOs of
both channels.
Table 23.
FIFO ready register bits description
Bit
Symbol
Description
7:6
FIFO Rdy[7:6]
unused; always 0
5
FIFO Rdy[5]
receive FIFO B status; related to DMA
4
FIFO Rdy[4]
receive FIFO A status; related to DMA
3:2
FIFO Rdy[3:2]
unused; always 0
1
FIFO Rdy[1]
transmit FIFO B status; related to DMA
0
FIFO Rdy[0]
transmit FIFO A status; related to DMA
The FIFO Rdy register is a read-only register that can be accessed when any of the two
UARTs is selected CS = 0, MCR[2] (FIFO Rdy Enable) is a logic 1, and loopback is
disabled. The address is 111.
SC68C752B_4
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Rev. 04 — 20 January 2010
30 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
8. Programmer’s guide
The base set of registers that is used during high-speed data transfer have a
straightforward access method. The extended function registers require special access
bits to be decoded along with the address lines. The following guide will help with
programming these registers. Note that the descriptions below are for individual register
access. Some streamlining through interleaving can be obtained when programming all
the registers.
Table 24.
Register programming guide
Command
Actions
Set baud rate to VALUE1, VALUE2
read LCR (03h), save in temp
set LCR (03h) to 80h
set DLL (00h) to VALUE1
set DLM (01h) to VALUE2
set LCR (03h) to temp
Set Xoff1, Xon1 to VALUE1, VALUE2
read LCR (03h), save in temp
set LCR (03h) to BFh
set Xoff1 (06h) to VALUE1
set Xon1 (04h) to VALUE2
set LCR (03h) to temp
Set Xoff2, Xon2 to VALUE1, VALUE2
read LCR (03h), save in temp
set LCR (03h) to BFh
set Xoff2 (07h) to VALUE1
set Xon2 (05h) to VALUE2
set LCR (03h) to temp
Set software flow control mode to VALUE
read LCR (03h), save in temp
set LCR (03h) to BFh
set EFR (02h) to VALUE
set LCR (03h) to temp
Set flow control threshold to VALUE
read LCR (03h), save in temp1
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to 40h + temp3
set TCR (06h) to VALUE
set MCR (04h) to temp3
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
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31 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Table 24.
Register programming guide …continued
Command
Actions
Set TX FIFO and RX FIFO thresholds
to VALUE
read LCR (03h), save in temp1
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to 40h + temp3
set TLR (07h) to VALUE
set MCR (04h) to temp3
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
Read FIFO Rdy register
read MCR (04h), save in temp1
set temp2 = temp1 × EFh [1]
set MCR (04h) = 40h + temp2
read FFR (07h), save in temp2
pass temp2 back to host
set MCR (04h) to temp1
Set prescaler value to divide-by-1
read LCR (03h), save in temp1
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to temp3 × 7Fh[1]
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
Set prescaler value to divide-by-4
read LCR (03h), save in temp1
set LCR (03h) to BFh
read EFR (02h), save in temp2
set EFR (02h) to 10h + temp2
set LCR (03h) to 00h
read MCR (04h), save in temp3
set MCR (04h) to temp3 + 80h
set LCR (03h) to BFh
set EFR (02h) to temp2
set LCR (03h) to temp1
[1]
× sign here means bit-AND.
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
32 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
9. Limiting values
Table 25. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol
Parameter
Conditions
VCC
supply voltage
Vn
voltage on any other pin at D7 to D0
at any input only pin
VO
output voltage
Tamb
ambient temperature
Tstg
storage temperature
operating in free-air
SC68C752B_4
Product data sheet
Min
Max
Unit
-
7
V
GND − 0.3
VCC + 0.3
V
GND − 0.3
5.3
V
−0.3
VCC + 0.3
V
−40
+85
°C
−65
+150
°C
© NXP B.V. 2010. All rights reserved.
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33 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
10. Static characteristics
Table 26. Static characteristics
Tolerance of VCC = ± 10 %.
Symbol Parameter
VCC
supply voltage
VI
input voltage
Conditions
VCC = 2.5 V
VCC = 3.3 V and 5 V
Max
Min
Min
Typ
VCC − 10 %
VCC
0
-
VCC
0
-
VCC
V
1.6
-
VCC
2.0
-
VCC
V
VCC + 10 % VCC − 10 %
Typ
Unit
VCC
Max
VCC + 10 % V
VIH
HIGH-level
input voltage
[1]
VIL
LOW-level input
voltage
[1]
-
-
0.65
-
-
0.8
V
VO
output voltage
[2]
0
-
VCC
0
-
VCC
V
IOH = −8 mA
[3]
-
-
-
2.0
-
-
V
IOH = −4 mA
[4]
-
-
-
2.0
-
-
V
IOH = −800 μA
[3]
1.85
-
-
-
-
-
V
IOH = −400 μA
[4]
VOH
HIGH-level
output voltage
LOW-level
output voltage
VOL
1.85
-
-
-
-
-
V
IOL = 8 mA
[3][5]
-
-
-
-
-
0.4
V
IOL = 4 mA
[4][5]
-
-
-
-
-
0.4
V
IOL = 2 mA
[3][5]
-
-
0.4
-
-
-
V
IOL = 1.6 mA
[4][5]
-
-
0.4
-
-
-
V
-
-
18
-
-
18
pF
−40
+25
+85
−40
+25
+85
°C
°C
Ci
input
capacitance
Tamb
ambient
temperature
Tj
junction
temperature
[6]
0
+25
+125
0
+25
+125
fXTAL1
frequency on
pin XTAL1
[7]
-
-
50
-
-
80
δ
clock duty cycle
-
50
-
-
50
-
-
-
3.5
-
-
4.5
mA
-
-
200
-
-
200
μA
ICC
supply current
operating
f = 5 MHz
[8]
ICC(sleep) sleep mode
supply current
[1]
Meets TTL levels, VIL(min) = 2 V and VIH(max) = 0.8 V on non-hysteresis inputs.
[2]
Applies for external output buffers.
[3]
These parameters apply for D[7:0].
[4]
These parameters apply for DTRA, DTRB, RTSA, RTSB, RXRDYA, RXRDYB, TXRDYA, TXRDYB, TXA, TXB.
[5]
Except XTAL2, VOL = 1 V typical.
[6]
These junction temperatures reflect simulated conditions. Absolute maximum junction temperature is 150 °C. The customer is
responsible for verifying junction temperature.
[7]
Applies to external clock; crystal oscillator max. 24 MHz.
[8]
Measurement condition, normal operation other than Sleep mode:
MHz
%
VCC = 3.3 V; Tamb = 25 °C. Full duplex serial activity on all two serial (UART) channels at the clock frequency specified in the
recommended operating conditions with divisor of 1.
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Rev. 04 — 20 January 2010
34 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
11. Dynamic characteristics
Table 27. Dynamic characteristics
Tamb = −40 °C to +85 °C; tolerance of VCC ± 10 %, unless specified otherwise.
Symbol
Parameter
Conditions
VCC = 2.5 V
VCC = 3.3 V and 5 V
Min
Max
Min
Max
Unit
td1
R/W to chip select
10
-
10
-
ns
td2
read cycle delay
25 pF load
20
-
20
-
ns
td3
delay from CS to data
25 pF load
-
77
-
26
ns
td4
data disable time
25 pF load
-
15
-
15
ns
td6
write cycle delay
25
-
25
-
ns
td7
delay from WRITE to output
25 pF load
-
100
-
33
ns
td8
delay to set interrupt from modem
input
25 pF load
-
100
-
24
ns
td9
delay to reset interrupt from READ
25 pF load
td10
delay from stop to set interrupt
td11
delay from READ to reset interrupt
td12
delay from start to set interrupt
25 pF load
-
100
-
24
ns
-
1TRCLK[1]
-
1TRCLK[1]
s
-
100
-
29
ns
-
delay from WRITE to reset interrupt
-
100
-
70
ns
td15
delay from stop to set RXRDY
-
1TRCLK[1]
-
1TRCLK[1]
s
td16
delay from READ to reset RXRDY
-
100
-
75
ns
td17
delay from WRITE to set TXRDY
-
100
-
70
ns
td18
delay from start to reset TXRDY
-
16TRCLK[1]
-
th2
R/W hold time from CS
10
-
10
-
ns
th3
data hold time
15
-
15
-
ns
th4
address hold time
15
-
15
-
ns
tWL
pulse width LOW
10
-
6
-
ns
tWH
pulse width HIGH
10
-
6
-
ns
-
48
-
80
[4]
24TRCLK
ns
[1]
delay from WRITE to transmit start
frequency on pin XTAL1
8TRCLK
100
[1]
td13
[2][3]
24TRCLK
[1]
td14
fXTAL1
8TRCLK
100
[1]
s
16TRCLK[1] s
MHz
t(RESET)
RESET pulse width
200
-
200
-
ns
tsu1
address setup time
10
-
10
-
ns
tsu2
data setup time
16
-
16
-
ns
tw1
CS strobe width
77
-
30
-
ns
[1]
RCLK is an internal signal derived from Divisor Latch LSB (DLL) and Divisor Latch MSB (DLM) divisor latches.
[2]
Applies to external clock; crystal oscillator max 24 MHz.
[3]
Maximum frequency = ---------------
[4]
Reset pulse must occur when CS is inactive.
1
t w ( clk )
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5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
11.1 Timing diagrams
valid address
A0 to A3
tsu1
valid address
th4
tw1
td2
CS
td4
td1
R/W
td3
D0 to D7
valid data
valid data
002aab087
Fig 14. General read timing
A0 to A3
valid address
tsu1
valid address
tw1
th4
CS
th2
td1
td6
R/W
tsu2
D0 to D7
th3
valid data
valid data
002aab088
Fig 15. General write timing
SC68C752B_4
Product data sheet
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36 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
active
CS (write)(1)
td7
RTSA, RTSB
DTRA, DTRB
change of state
change of state
CDA, CDB
CTSA, CTSB
DSRA, DSRB
change of state
td8
IRQ
change of state
td8
active
active
active
td9
CS (read)(2)
active
active
active
td8
change of state
RIA, RIB
002aab089
(1) CS timing during a write cycle. See Figure 15.
(2) CS timing during a read cycle. See Figure 14.
Fig 16. Modem input/output timing
tWL
tWH
external clock
tw(clk)
002aac357
1
f XTAL1 = --------------t w ( clk )
Fig 17. External clock timing
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
37 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Start
bit
RXA, RXB
parity
bit
data bits (0 to 7)
D0
D1
D2
D3
D4
D5
D6
Stop
bit
next
data
Start
bit
D7
5 data bits
6 data bits
td10
7 data bits
active
IRQ
td11
CS (read)
active
16 baud rate clock
002aab090
Fig 18. Receive timing
Start
bit
RXA, RXB
parity
bit
data bits (0 to 7)
D0
D1
D2
D3
D4
D5
D6
Stop
bit
next
data
Start
bit
D7
td15
active data
ready
RXRDYA,
RXRDYB
td16
CS (read)
active
002aab091
Fig 19. Receive ready timing in non-FIFO mode
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
38 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Start
bit
D0
RXA, RXB
parity
bit
data bits (0 to 7)
D1
D2
D3
D4
D5
D6
Stop
bit
D7
first byte that
reaches the
trigger level
td15
active data
ready
RXRDYA,
RXRDYB
td16
CS (read)
active
002aab092
Fig 20. Receive ready timing in FIFO mode
Start
bit
data bits (0 to 7)
D0
TXA, TXB
parity
bit
D1
D2
D3
D4
D5
D6
Stop
bit
next
data
Start
bit
D7
5 data bits
6 data bits
7 data bits
IRQ
td12
active
transmitter ready
td14
td13
CS (write)
active
active
16 baud rate clock
002aab093
Fig 21. Transmit timing
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
39 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Start
bit
TXA,
TXB
D0
CS (write)
active
D0 to D7
byte #1
parity
bit
data bits (0 to 7)
D1
D2
D3
D4
D5
D6
Stop
bit
next
data
Start
bit
D7
td18
td17
active
transmitter ready
TXRDYA,
TXRDYB
transmitter
not ready
002aab094
Fig 22. Transmit ready timing in non-FIFO mode
start
bit
data bits (0 to 7)
D0
TXA,
TXB
parity
bit
D1
D2
D3
D4
D5
D6
stop
bit
D7
5 data bits
6 data bits
7 data bits
CS (write)
active
td18
D0 to D7
byte #64
td17
TXRDYA,
TXRDYB
trigger
lead
002aab377
Fig 23. Transmit ready timing in FIFO mode
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
40 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
12. Package outline
LQFP48: plastic low profile quad flat package; 48 leads; body 7 x 7 x 1.4 mm
SOT313-2
c
y
X
36
25
A
37
24
ZE
e
E HE
A A2
(A 3)
A1
w M
θ
bp
pin 1 index
Lp
L
13
48
1
detail X
12
ZD
e
v M A
w M
bp
D
B
HD
v M B
0
2.5
5 mm
scale
DIMENSIONS (mm are the original dimensions)
UNIT
A
max.
A1
A2
A3
bp
c
D (1)
E (1)
e
HD
HE
L
Lp
v
w
y
mm
1.6
0.20
0.05
1.45
1.35
0.25
0.27
0.17
0.18
0.12
7.1
6.9
7.1
6.9
0.5
9.15
8.85
9.15
8.85
1
0.75
0.45
0.2
0.12
0.1
Z D (1) Z E (1)
θ
0.95
0.55
7
o
0
0.95
0.55
o
Note
1. Plastic or metal protrusions of 0.25 mm maximum per side are not included.
REFERENCES
OUTLINE
VERSION
IEC
JEDEC
SOT313-2
136E05
MS-026
JEITA
EUROPEAN
PROJECTION
ISSUE DATE
00-01-19
03-02-25
Fig 24. Package outline SOT313-2 (LQFP48)
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
41 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
HVQFN32: plastic thermal enhanced very thin quad flat package; no leads;
32 terminals; body 5 x 5 x 0.85 mm
A
B
D
SOT617-1
terminal 1
index area
A
A1
E
c
detail X
C
e1
e
1/2
e b
9
y
y1 C
v M C A B
w M C
16
L
17
8
e
e2
Eh
1/2
1
terminal 1
index area
e
24
32
25
X
Dh
0
2.5
5 mm
scale
DIMENSIONS (mm are the original dimensions)
UNIT
A(1)
max.
A1
b
c
D (1)
Dh
E (1)
Eh
e
e1
e2
L
v
w
y
y1
mm
1
0.05
0.00
0.30
0.18
0.2
5.1
4.9
3.25
2.95
5.1
4.9
3.25
2.95
0.5
3.5
3.5
0.5
0.3
0.1
0.05
0.05
0.1
Note
1. Plastic or metal protrusions of 0.075 mm maximum per side are not included.
REFERENCES
OUTLINE
VERSION
IEC
JEDEC
JEITA
SOT617-1
---
MO-220
---
EUROPEAN
PROJECTION
ISSUE DATE
01-08-08
02-10-18
Fig 25. Package outline SOT617-1 (HVQFN32)
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
42 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
13. Soldering of SMD packages
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 “Surface mount reflow
soldering description”.
13.1 Introduction to soldering
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for fine pitch SMDs. Reflow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
13.2 Wave and reflow soldering
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
• Through-hole components
• Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reflow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature profile. Leaded packages,
packages with solder balls, and leadless packages are all reflow solderable.
Key characteristics in both wave and reflow soldering are:
•
•
•
•
•
•
Board specifications, including the board finish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Package placement
Inspection and repair
Lead-free soldering versus SnPb soldering
13.3 Wave soldering
Key characteristics in wave soldering are:
• Process issues, such as application of adhesive and flux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
• Solder bath specifications, including temperature and impurities
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Product data sheet
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Rev. 04 — 20 January 2010
43 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
13.4 Reflow soldering
Key characteristics in reflow soldering are:
• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see Figure 26) than a SnPb process, thus
reducing the process window
• Solder paste printing issues including smearing, release, and adjusting the process
window for a mix of large and small components on one board
• Reflow temperature profile; this profile includes preheat, reflow (in which the board is
heated to the peak temperature) and cooling down. It is imperative that the peak
temperature is high enough for the solder to make reliable solder joints (a solder paste
characteristic). In addition, the peak temperature must be low enough that the
packages and/or boards are not damaged. The peak temperature of the package
depends on package thickness and volume and is classified in accordance with
Table 28 and 29
Table 28.
SnPb eutectic process (from J-STD-020C)
Package thickness (mm)
Package reflow temperature (°C)
Volume (mm3)
< 350
≥ 350
< 2.5
235
220
≥ 2.5
220
220
Table 29.
Lead-free process (from J-STD-020C)
Package thickness (mm)
Package reflow temperature (°C)
Volume (mm3)
< 350
350 to 2000
> 2000
< 1.6
260
260
260
1.6 to 2.5
260
250
245
> 2.5
250
245
245
Moisture sensitivity precautions, as indicated on the packing, must be respected at all
times.
Studies have shown that small packages reach higher temperatures during reflow
soldering, see Figure 26.
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
44 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
maximum peak temperature
= MSL limit, damage level
temperature
minimum peak temperature
= minimum soldering temperature
peak
temperature
time
001aac844
MSL: Moisture Sensitivity Level
Fig 26. Temperature profiles for large and small components
For further information on temperature profiles, refer to Application Note AN10365
“Surface mount reflow soldering description”.
14. Abbreviations
Table 30.
Abbreviations
Acronym
Description
CPU
Central Processing Unit
DMA
Direct Memory Access
FIFO
First In/First Out
LSB
Least Significant Bit
MSB
Most Significant Bit
PCB
Printed-Circuit Board
TTL
Transistor-Transistor Logic
UART
Universal Asynchronous Receiver and Transmitter
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
45 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
15. Revision history
Table 31.
Revision history
Document ID
Release date
Data sheet status
Change notice
Supersedes
SC68C752B_4
20100120
Product data sheet
-
SC68C752B_3
Modifications:
•
The format of this data sheet has been redesigned to comply with the new identity guidelines of
NXP Semiconductors.
•
•
•
Legal texts have been adapted to the new company name where appropriate.
Descriptive title of data sheet modified: changed from “Motorola” to “68 mode”
Section 2 “Features”:
– 1st bullet item changed from “Motorola μP interface” to “68 mode (Motorola) μP interface”
– 10th bullet item changed from “5 V tolerant inputs” to “5 V tolerant on input only pins”
– 10th bullet item added Footnote 1
•
•
•
Table 2 “Pin description”: added Table note [1] and its reference at HVQFN32 pin 13.
Section 7.11 “Divisor latches (DLL, DLM)”: changed from “DLH” to “DLM” (and throughout data
sheet)
Table 25 “Limiting values”:
– removed specification for VI
– added specification for Vn
– removed table note [1] and its reference (statement is now covered in Section 16.3)
•
Table 26 “Static characteristics”: parameter for ICC(sleep) changed from “sleep current” to “sleep
mode supply current”
•
Table 27 “Dynamic characteristics”:
– added Table note [4] and its reference at t(RESET)
– split symbol/parameter “tw1, tw2, clock cycle period” to two symbol/parameters, “tWH, pulse
width HIGH” and “tWL, pulse width LOW”
– denominator in equation in Table note [3] changed from “tw3” to “tw(clk)”
•
Figure 17 “External clock timing”:
– changed symbol from “tw1” to “tWH”
– changed symbol from “tw2” to “tWL”
– changed symbol from “tw3” to “tw(clk)” (in both drawing and equation denominator)
SC68C752B_3
20051129
Product data sheet
-
SC68C752B_2
SC68C752B_2
(9397 750 14963)
20050428
Product data sheet
-
SC68C752B_1
SC68C752B_1
(9397 750 13857)
20050329
Product data sheet
-
-
SC68C752B_4
Product data sheet
© NXP B.V. 2010. All rights reserved.
Rev. 04 — 20 January 2010
46 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
16. Legal information
16.1 Data sheet status
Document status[1][2]
Product status[3]
Definition
Objective [short] data sheet
Development
This document contains data from the objective specification for product development.
Preliminary [short] data sheet
Qualification
This document contains data from the preliminary specification.
Product [short] data sheet
Production
This document contains the product specification.
[1]
Please consult the most recently issued document before initiating or completing a design.
[2]
The term ‘short data sheet’ is explained in section “Definitions”.
[3]
The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
16.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
16.3 Disclaimers
General — Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations or
warranties, expressed or implied, as to the accuracy or completeness of such
information and shall have no liability for the consequences of use of such
information.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is at the customer’s own risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) may cause permanent
damage to the device. Limiting values are stress ratings only and operation of
the device at these or any other conditions above those given in the
Characteristics sections of this document is not implied. Exposure to limiting
values for extended periods may affect device reliability.
Terms and conditions of sale — NXP Semiconductors products are sold
subject to the general terms and conditions of commercial sale, as published
at http://www.nxp.com/profile/terms, including those pertaining to warranty,
intellectual property rights infringement and limitation of liability, unless
explicitly otherwise agreed to in writing by NXP Semiconductors. In case of
any inconsistency or conflict between information in this document and such
terms and conditions, the latter will prevail.
No offer to sell or license — Nothing in this document may be interpreted or
construed as an offer to sell products that is open for acceptance or the grant,
conveyance or implication of any license under any copyrights, patents or
other industrial or intellectual property rights.
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from national authorities.
16.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
17. Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
SC68C752B_4
Product data sheet
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Rev. 04 — 20 January 2010
47 of 48
SC68C752B
NXP Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
18. Contents
1
2
3
4
5
5.1
5.2
6
6.1
6.2
6.2.1
6.2.2
6.3
6.3.1
6.3.2
6.3.3
6.3.3.1
6.4
6.5
6.5.1
6.5.2
6.6
6.6.1
6.6.1.1
6.6.1.2
6.6.2
6.6.2.1
6.6.2.2
6.7
6.8
6.9
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
General description . . . . . . . . . . . . . . . . . . . . . . 1
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ordering information . . . . . . . . . . . . . . . . . . . . . 2
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pinning information . . . . . . . . . . . . . . . . . . . . . . 4
Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 5
Functional description . . . . . . . . . . . . . . . . . . . 7
Trigger levels . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Hardware flow control . . . . . . . . . . . . . . . . . . . . 7
Auto-RTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Auto-CTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Software flow control . . . . . . . . . . . . . . . . . . . . 9
Receive flow control . . . . . . . . . . . . . . . . . . . . 10
Transmit flow control. . . . . . . . . . . . . . . . . . . . 10
Software flow control example . . . . . . . . . . . . 11
Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Interrupt mode operation . . . . . . . . . . . . . . . . 14
Polled mode operation . . . . . . . . . . . . . . . . . . 14
DMA operation . . . . . . . . . . . . . . . . . . . . . . . . 15
Single DMA transfers
(DMA mode 0/FIFO disable). . . . . . . . . . . . . . 15
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Block DMA transfers (DMA mode 1). . . . . . . . 16
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Break and time-out conditions . . . . . . . . . . . . 17
Programmable baud rate generator . . . . . . . . 17
Register descriptions . . . . . . . . . . . . . . . . . . . 19
Receiver Holding Register (RHR). . . . . . . . . . 21
Transmit Holding Register (THR) . . . . . . . . . . 21
FIFO Control Register (FCR) . . . . . . . . . . . . . 22
Line Control Register (LCR) . . . . . . . . . . . . . . 23
Line Status Register (LSR) . . . . . . . . . . . . . . . 24
Modem Control Register (MCR) . . . . . . . . . . . 25
Modem Status Register (MSR) . . . . . . . . . . . . 26
Interrupt Enable Register (IER) . . . . . . . . . . . 27
Interrupt Identification Register (IIR). . . . . . . . 28
Enhanced Feature Register (EFR) . . . . . . . . . 29
Divisor latches (DLL, DLM). . . . . . . . . . . . . . . 29
Transmission Control Register (TCR). . . . . . . 29
Trigger Level Register (TLR) . . . . . . . . . . . . . 30
FIFO ready register . . . . . . . . . . . . . . . . . . . . 30
8
9
10
11
11.1
12
13
13.1
13.2
13.3
13.4
14
15
16
16.1
16.2
16.3
16.4
17
18
Programmer’s guide . . . . . . . . . . . . . . . . . . . .
Limiting values . . . . . . . . . . . . . . . . . . . . . . . .
Static characteristics . . . . . . . . . . . . . . . . . . .
Dynamic characteristics. . . . . . . . . . . . . . . . .
Timing diagrams. . . . . . . . . . . . . . . . . . . . . . .
Package outline. . . . . . . . . . . . . . . . . . . . . . . .
Soldering of SMD packages . . . . . . . . . . . . . .
Introduction to soldering. . . . . . . . . . . . . . . . .
Wave and reflow soldering. . . . . . . . . . . . . . .
Wave soldering . . . . . . . . . . . . . . . . . . . . . . .
Reflow soldering . . . . . . . . . . . . . . . . . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . .
Legal information . . . . . . . . . . . . . . . . . . . . . .
Data sheet status . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information . . . . . . . . . . . . . . . . . . . .
Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
33
34
35
36
41
43
43
43
43
44
45
46
47
47
47
47
47
47
48
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2010.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 20 January 2010
Document identifier: SC68C752B_4
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