PHILIPS SC68C752BIBS

SC68C752B
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte
FIFOs and Motorola µP interface
Rev. 03 — 29 November 2005
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
TXRDY/RXRDY 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 TX signal and
receives characters on the RX 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 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
5 V tolerant inputs
Software selectable baud rate generator
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
■
■
■
■
■
■
■
■
■
■
■
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
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
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
2 of 49
SC68C752B
Philips 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
XTAL2
Fig 1. Block diagram of SC68C752B
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
3 of 49
SC68C752B
Philips 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
42 VCC
41 RIA
43 TXRDYA
44 D0
45 D1
46 D2
47 D3
48 D4
5.1 Pinning
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
RIB 21
30 IRQ
RTSB 22
DSRB 20
VCC 19
RXRDYB 18
GND 17
CDB 16
R/W 15
XTAL2 14
XTAL1 13
SC68C752BIB48
002aab018
25 CTSA
26 VCC
27 D0
28 D1
29 D2
30 D3
32 D5
terminal 1
index area
31 D4
Fig 2. 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
n.c. 14
RTSB 15
GND 13
R/W 12
XTAL2 11
XTAL1 10
A3
9
SC68C752BIBS
002aac014
Transparent top view
Fig 3. Pin configuration for HVQFN32
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
4 of 49
SC68C752B
Philips 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
LQFP48
HVQFN32
A0
28
19
I
Address 0 select bit. Internal registers address selection.
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.)
CDA, CDB
40, 16
-
I
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).
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, CTSB
38, 23
25, 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 CTS
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 to D7
44, 45, 46, 27, 28, 29, I/O
47, 48, 1, 30, 31, 32,
2, 3
1, 2
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.
DSRA, DSRB
39, 20
-
I
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).
DTRA, DTRB
34, 35
-
O
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 DTR output 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.
GND
17, 24
13
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.
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
5 of 49
SC68C752B
Philips 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
I
A logic LOW on this pin will transfer the contents of the data bus (D[0:7])
from an external CPU to an internal register that is defined by address
bits A[0:2]. A logic HIGH on this pin will load the contents of an internal
register defined by address bits A[0:2] on the SC68C752B data bus
(D[0:7]) for access by an external CPU.
12, 25, 29, 14, 20
37
-
not connected
OPA, OPB
32, 9
22, 7
O
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.
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.
RIA, RIB
41, 21
-
I
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).
RTSA, RTSB
33, 22
23, 16
O
Request to Send (active LOW). These outputs are associated with
individual UART Channel A and Channel B. A logic 0 on the RTS 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, RXB
5, 4
4, 3
I
Receive data input. These inputs are associated with individual serial
channel data to the SC68C752B. During the local Loopback mode,
these RX input pins are disabled and TX data is connected to the UART
RX input internally.
RXRDYA,
RXRDYB
31, 18
-
O
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 RX FIFO is empty.
TXA, TXB
7, 8
5, 6
O
Transmit data A, B. These outputs are associated with individual serial
transmit channel data from the SC68C752B. During the local Loopback
mode, the TX output pin is disabled and TX data is internally connected
to the UART RX input.
TXRDYA,
TXRDYB
43, 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.
LQFP48
HVQFN32
R/W
15
12
n.c.
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
6 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
Table 2:
Symbol
Pin description …continued
Pin
Type
Description
26
I
Power supply input.
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.
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.
LQFP48
HVQFN32
VCC
19, 42
XTAL1
XTAL2
Table 3:
Channel selection using CS pin
CS
A3
UART channel
1
-
none
0
0
Channel A
0
1
Channel B
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
7 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
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 RXRDY and TXRDY 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 RTS output and CTS 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, CTS must be active before the UART can transmit data.
Auto-RTS only activates the RTS output when there is enough room in the FIFO to receive
data and de-activates the RTS output when the RX FIFO is sufficiently full. The halt and
resume trigger levels in the TCR determine the levels at which RTS is
activated/deactivated.
If both Auto-CTS and Auto-RTS are enabled, when RTS is connected to CTS, data
transmission does not occur unless the receiver 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.
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
8 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
UART 1
UART 2
SERIAL TO
PARALLEL
RX
PARALLEL
TO SERIAL
TX
RX
FIFO
TX
FIFO
FLOW
CONTROL
RTS
CTS
FLOW
CONTROL
D7 to D0
D7 to D0
PARALLEL
TO SERIAL
TX
SERIAL TO
PARALLEL
RX
TX
FIFO
RX
FIFO
FLOW
CONTROL
CTS
RTS
FLOW
CONTROL
002aaa228
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 RTS functional timing. The receiver FIFO trigger
levels used in Auto-RTS are stored in the TCR. RTS is active if the RX FIFO level is below
the halt trigger level in TCR[3:0]. When the receiver FIFO halt trigger level is reached,
RTS 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 RTS until it has begun
sending the additional byte. RTS 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.
RX
Start
byte N
Stop
Start
byte N + 1
Stop
Start
RTS
R/W
1
2
N
N+1
002aab086
(1) N = receiver FIFO trigger level.
(2) The two blocks in dashed lines cover the case where an additional byte is sent, as described in Section 6.2.1.
Fig 5. RTS functional timing
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
9 of 49
SC68C752B
Philips 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 CTS before sending the next data byte. When CTS is
active, the transmitter sends the next byte. To stop the transmitter from sending the
following byte, CTS 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, CTS 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.
TX
Start
byte 0 to 7
Start
Stop
byte 0 to 7
Stop
CTS
002aaa227
(1) When CTS is LOW, the transmitter keeps sending serial data out.
(2) When CTS 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.
(3) When CTS goes from HIGH to LOW, the transmitter begins sending data again.
Fig 6. CTS 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[0:3])
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_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
10 of 49
SC68C752B
Philips 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_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
11 of 49
SC68C752B
Philips 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
compare
programmed
Xon-Xoff
characters
Xoff2 WORD
002aaa229
Fig 7. Software flow control example
6.3.3.1
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_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
12 of 49
SC68C752B
Philips 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, DLH, 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
TX
RESET
HIGH
RTS
RESET
HIGH
DTR
RESET
HIGH
RXRDY
RESET
HIGH
TXRDY
RESET
LOW
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SC68C752B
Philips 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 0:3, 5:7. 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
level
Interrupt type
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)
read IIR or a write to the THR
(FIFO disable)
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
RTS pin or CTS pin change state from read IIR
active (LOW) to inactive (HIGH)
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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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
Philips 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 TXRDY and RXRDY in DMA mode 0/FIFO disable.
TX
RX
RXRDY
TXRDY
at least one
location filled
wrptr
at least one
location filled
rdptr
RXRDY
TXRDY
wrptr
FIFO EMPTY
rdptr
FIFO EMPTY
002aaa232
Fig 10. TXRDY and RXRDY in DMA mode 0/FIFO disable
6.6.1.1
Transmitter
When empty, the TXRDY signal becomes active. TXRDY will go inactive after one
character has been loaded into it.
6.6.1.2
Receiver
RXRDY is active when there is at least one character in the FIFO. It becomes inactive
when the receiver is empty.
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Philips 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 TXRDY and RXRDY in DMA mode 1.
wrptr
TX
trigger
level
TXRDY
RX
RXRDY
rdptr
at least one
location filled
FIFO full
trigger
level
wrptr
TXRDY
RXRDY
rdptr
FIFO EMPTY
002aaa234
Fig 11. TXRDY and RXRDY in DMA mode 1
6.6.2.1
Transmitter
TXRDY 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
RXRDY 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 RX 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, RX, is idle (see Section 6.8 “Break and time-out
conditions”).
• The TX FIFO and TX 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 RX 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 RX line, when there is any change in the
state of the modem input pins, or if data is written to the TX FIFO.
Remark: Writing to the divisor latches, DLL and DLH, 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 DLH.
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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, RX, has been HIGH for
4 character time. The receiver line is sampled midway through each bit.
When a break condition occurs, the TX 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 × the baud rate. The
formula for the divisor is:
crystal input frequency
 XTAL1
 --------------------------------------------------------------------------
prescaler
divisor = --------------------------------------------------------------------------------( desired baud rate × 16 )
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 DLH must be written to in order to program the baud rate. DLL and DLH are the
least significant and most significant byte of the baud rate divisor. If DLL and DLH 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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SC68C752B
Philips 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_3
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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Philips 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]
Modem Control Register [1]
1
0
1
Line Status Register (LSR)
1
1
0
Modem Status Register (MSR)
1
1
1
ScratchPad Register (SPR)
ScratchPad Register
0
0
0
Divisor Latch LSB (DLL) [2] [3]
divisor latch LSB [2] [3]
(DLH) [2] [3]
0
1
Divisor Latch MSB
0
1
0
Enhanced Feature Register (EFR) [2] [4]
Enhanced Feature Register [2] [4]
1
0
0
Xon1 word [2] [4]
Xon1 word [2] [4]
1
0
1
Xon2 word [2] [4]
Xon2 word [2] [4]
word [2] [4]
Xoff1 word [2] [4]
Xoff2 word [2] [4]
1
1
0
Xoff1
1
1
1
Xoff2 word [2] [4]
1
1
0
Transmission Control Register (TCR) [2] [5] Transmission Control Register [2] [5]
1
1
1
Trigger Level Register (TLR) [2] [5]
1
1
1
FIFO ready
Trigger Level Register [2] [5]
register [2] [6]
[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_3
Product data sheet
divisor latch MSB [2] [3]
0
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Philips 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
Xoff [2]
Sleep
mode [2]
modem
status
interrupt
receive
THR
line status empty
interrupt
interrupt
0
0
1
IER
CTS
RTS
interrupt interrupt
enable [2] enable [2]
0
1
0
FCR
RX
trigger
level
(MSB)
RX
trigger
level
(LSB)
TX trigger TX trigger DMA
level
level
mode
(MSB) [2] (LSB) [2]
select
TX FIFO
reset
RX FIFO FIFO
reset
enable
W
0
1
0
IIR
FCR[0]
FCR[0]
CTS,
RTS
interrupt
priority
bit 2
interrupt
priority
bit 1
interrupt
priority
bit 0
interrupt
status
R
0
1
1
LCR
DLAB
break
control
bit
set parity parity
type
select
parity
enable
number of word
stop bits length
bit 1
word
length
bit 0
R/W
1
0
0
MCR
1× or
1×/4
clock [2]
TCR and Xon
TLR
Any [2]
enable [2]
enable
loopback
OPA/
OPB
control
FIFO
ready
enable
RTS
DTR
R/W
1
0
1
LSR
error in
THR and THR
RX FIFO TSR
empty
empty
break
interrupt
framing
error
parity
error
overrun
error
data in
receiver
R
1
1
0
MSR
CD
RI
DSR
CTS
∆CD
∆RI
∆DSR
∆CTS
R
1
1
1
SPR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
1
0
TCR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
1
1
TLR
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
1
1
1
FIFO Rdy 0
0
RX FIFO
B status
RX FIFO
A status
0
0
TX FIFO TX FIFO
B status A status
R
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
R/W
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
bit 9
bit 8
R/W
Xoff
RX data R/W
available
interrupt
Special register set [3]
0
0
0
DLL
0
0
1
DLH
Enhanced register
set [4]
0
1
0
EFR
Auto
CTS
Auto
RTS
software
special
enable
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.
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5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
[4]
Enhanced Feature Register; XON1/XON2 and XOFF1/XOFF2 are accessible only when LCR is set to ‘BFh’.
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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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 RX 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 TX 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 TX 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 RX 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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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 TX output is forced to a logic 0 state). This
condition exists until disabled by setting LCR[6] to a logic 0.
logic 0 = no TX break condition (normal default condition)
logic 1 = forces the transmitter output (TX) 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 logical 1 for
the transmit and receive data.
LCR[5] = logic 1 and LCR[4] = logic 1: parity bit is forced to a logical 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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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,
RX was LOW for one character time frame.
3
LSR[3]
Framing error.
logic 0 = no framing error in data being read from RX FIFO (normal default
condition)
logic 1 = Framing error occurred in data being read from RX 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 RX 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 RX FIFO
When the LSR is read, LSR[4:2] reflect the error bits (BI, FE, PE) of the character at the
top of the RX FIFO (next character to be read). The LSR[4:2] registers do not physically
exist, as the data read from the RX 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 RX 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 RX FIFO read pointer. The RX FIFO
read pointer is incremented by reading the RHR.
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
25 of 49
SC68C752B
Philips 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 TX output is
looped back to the RX 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 RTS output to inactive (HIGH)
logic 1 = force RTS output to active (LOW). In Loopback mode, controls
MSR[4]. If Auto-RTS is enabled, the RTS output is controlled by
hardware flow control.
0
MCR[0]
DTR
logic 0 = force DTR output to inactive (HIGH)
logic 1 = force DTR 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
Philips 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, logical 1). This bit is the complement of the CD input during
normal mode. During internal Loopback mode, it is equivalent to MCR[3].
6
MSR[6] [1]
RI (active HIGH, logical 1). This bit is the complement of the RI input during
normal mode. During internal Loopback mode, it is equivalent to MCR[2].
5
MSR[5] [1]
DSR (active HIGH, logical 1). This bit is the complement of the DSR input
during normal mode. During internal Loopback mode, it is equivalent MCR[0].
4
MSR[4] [1]
CTS (active HIGH, logical 1). This bit is the complement of the CTS input
during normal mode. During internal Loopback mode, it is equivalent to
MCR[1].
3
MSR[3]
∆CD. Indicates that CD input (or MCR[3] in Loopback mode) has changed
state. Cleared on a read.
2
MSR[2]
∆RI. Indicates that RI input (or MCR[2] in Loopback mode) has changed state
from LOW to HIGH. Cleared on a read.
1
MSR[1]
∆DSR. Indicates that DSR input (or MCR[0] in Loopback mode) has changed
state. Cleared on a read.
0
MSR[0]
∆CTS. Indicates that CTS input (or MCR[1] in Loopback mode) has changed
state. Cleared on a read.
[1]
The primary inputs RI, CD, CTS, DSR are all active LOW, but their registered equivalents in the MSR and
MCR (in Loopback mode) registers are active HIGH.
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SC68C752B
Philips 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 CTS/RTS 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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Philips 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:
Interrupt Identification Register bits description
Bit
Symbol
Description
7:6
IIR[7:6]
Mirror the contents of FCR[0].
5
IIR[5]
RTS/CTS 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
CTS, RTS change of state from
active (LOW) to inactive (HIGH)
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SC68C752B
Philips 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 CTS 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 RTS 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 logical 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[0:3])” on page 10.
7.11 Divisor latches (DLL, DLH)
These are two 8-bit registers which store the 16-bit divisor for generation of the baud clock
in the baud rate generator. DLH stores the most significant part of the divisor. DLL stores
the least significant part of the divisor.
Note that DLL and DLH 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 RX 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]
RX FIFO trigger level to resume transmission (0 bytes to 60 bytes).
3:0
TCR[3:0]
RX 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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SC68C752B
Philips 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]
RX FIFO trigger levels (4 to 60), number of characters available.
3:0
TLR[3:0]
TX 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 logical 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]
RX FIFO B status; related to DMA
4
FIFO Rdy[4]
RX FIFO A status; related to DMA
3:2
FIFO Rdy[3:2]
unused; always 0
1
FIFO Rdy[1]
TX FIFO B status; related to DMA
0
FIFO Rdy[0]
TX 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.
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SC68C752B
Philips 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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SC68C752B
Philips 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 BF
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_3
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SC68C752B
Philips 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). [1]
Symbol
Parameter
VCC
Min
Max
Unit
supply voltage
-
7
V
VI
input voltage
−0.3
VCC + 0.3
V
VO
output voltage
−0.3
VCC + 0.3
V
Tamb
ambient temperature
−40
+85
°C
Tstg
storage temperature
−65
+150
°C
[1]
Conditions
operating in free-air
Stresses beyond those listed under Table 25 “Limiting values” may cause permanent damage to the device.
These are stress ratings only, and functional operation of the device at these or any other conditions
beyond those indicated under recommended operating conditions is not implied. Exposure to
absolute-maximum-rated conditions for extended periods may affect device reliability.
SC68C752B_3
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34 of 49
SC68C752B
Philips 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
Conditions
VCC = 2.5 V
Min
Typ
Max
VCC = 3.3 V and 5 V
Min
Typ
Unit
Max
VCC
supply voltage
VCC − 10 % VCC
VCC + 10 % VCC − 10 % VCC
VCC + 10 % V
VI
input voltage
0
-
VCC
0
-
VCC
V
1.6
-
VCC
2.0
-
VCC
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]
1.85
-
-
-
-
-
V
LOW-level
IOL = 8 mA
output voltage [5] I = 4 mA
OL
[3]
-
-
-
-
-
0.4
V
[4]
-
-
-
-
-
0.4
V
IOL = 2 mA
[3]
-
-
0.4
-
-
-
V
IOL = 1.6 mA
[4]
-
-
0.4
-
-
-
V
-
-
18
-
-
18
pF
−40
+25
+85
−40
+25
+85
°C
VOH
VOL
HIGH-level
output voltage
Ci
input
capacitance
Tamb
ambient
temperature
Tj
junction
temperature
[6]
0
+25
+125
0
+25
+125
°C
fXTAL1
frequency on pin
XTAL1
[7]
-
-
50
-
-
80
MHz
δ
clock duty cycle
-
50
-
-
50
-
%
supply current
ICC
operating
f = 5 MHz
ICC(sleep) sleep current
[8]
-
-
3.5
-
-
4.5
mA
-
-
200
-
-
200
µA
[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:
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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Philips 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
-
100
-
24
ns
td10
delay from stop to set interrupt
-
1TRCLK [1]
-
1TRCLK [1]
s
td11
delay from READ to reset interrupt
-
100
-
29
ns
td12
delay from start to set interrupt
td13
delay from WRITE to transmit start
td14
delay from WRITE to reset interrupt
25 pF load
8TRCLK
-
100
[1]
-
24TRCLK
[1]
100
td15
delay from stop to set RXRDY
-
1TRCLK
td16
delay from READ to reset RXRDY
-
100
8TRCLK
100
[1]
[1]
-
ns
24TRCLK
[1]
70
1TRCLK
s
ns
[1]
s
75
ns
70
ns
td17
delay from WRITE to set TXRDY
-
100
-
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
tw1, tw2
clock cycle period
10
-
6
-
ns
-
48
-
80
200
-
200
-
[2] [3]
16TRCLK [1] s
fXTAL1
frequency on pin XTAL1
t(RESET)
RESET pulse width
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 = -------
ns
1
t 3w
SC68C752B_3
Product data sheet
MHz
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Rev. 03 — 29 November 2005
36 of 49
SC68C752B
Philips Semiconductors
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
td1
th2
td6
R/W
tsu2
D0 to D7
th3
valid data
valid data
002aab088
Fig 15. General write timing
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
37 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
CS (write)(1)
active
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
tw2
tw1
EXTERNAL
CLOCK
tw3
002aac020
1
f XTAL1 = ------t w3
Fig 17. External clock timing
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
38 of 49
SC68C752B
Philips 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_3
Product data sheet
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Rev. 03 — 29 November 2005
39 of 49
SC68C752B
Philips 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
active
TX ready
td12
td14
td13
CS (write)
active
active
16 baud rate clock
002aab093
Fig 21. Transmit timing
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
40 of 49
SC68C752B
Philips 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_3
Product data sheet
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Rev. 03 — 29 November 2005
41 of 49
SC68C752B
Philips 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_3
Product data sheet
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Rev. 03 — 29 November 2005
42 of 49
SC68C752B
Philips 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
16
y
y1 C
v M C A B
w M C
b
9
L
17
8
e
e2
Eh
1/2 e
1
terminal 1
index area
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_3
Product data sheet
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Rev. 03 — 29 November 2005
43 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
13. Soldering
13.1 Introduction to soldering surface mount packages
This text gives a very brief insight to a complex technology. A more in-depth account of
soldering ICs can be found in our Data Handbook IC26; Integrated Circuit Packages
(document order number 9398 652 90011).
There is no soldering method that is ideal for all surface mount IC packages. Wave
soldering can still be used for certain surface mount ICs, but it is not suitable for fine pitch
SMDs. In these situations reflow soldering is recommended.
13.2 Reflow soldering
Reflow soldering requires solder paste (a suspension of fine solder particles, flux and
binding agent) to be applied to the printed-circuit board by screen printing, stencilling or
pressure-syringe dispensing before package placement. Driven by legislation and
environmental forces the worldwide use of lead-free solder pastes is increasing.
Several methods exist for reflowing; for example, convection or convection/infrared
heating in a conveyor type oven. Throughput times (preheating, soldering and cooling)
vary between 100 seconds and 200 seconds depending on heating method.
Typical reflow peak temperatures range from 215 °C to 270 °C depending on solder paste
material. The top-surface temperature of the packages should preferably be kept:
• below 225 °C (SnPb process) or below 245 °C (Pb-free process)
– for all BGA, HTSSON..T and SSOP..T packages
– for packages with a thickness ≥ 2.5 mm
– for packages with a thickness < 2.5 mm and a volume ≥ 350 mm3 so called
thick/large packages.
• below 240 °C (SnPb process) or below 260 °C (Pb-free process) for packages with a
thickness < 2.5 mm and a volume < 350 mm3 so called small/thin packages.
Moisture sensitivity precautions, as indicated on packing, must be respected at all times.
13.3 Wave soldering
Conventional single wave soldering is not recommended for surface mount devices
(SMDs) or printed-circuit boards with a high component density, as solder bridging and
non-wetting can present major problems.
To overcome these problems the double-wave soldering method was specifically
developed.
If wave soldering is used the following conditions must be observed for optimal results:
• Use a double-wave soldering method comprising a turbulent wave with high upward
pressure followed by a smooth laminar wave.
• For packages with leads on two sides and a pitch (e):
– larger than or equal to 1.27 mm, the footprint longitudinal axis is preferred to be
parallel to the transport direction of the printed-circuit board;
SC68C752B_3
Product data sheet
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44 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
– smaller than 1.27 mm, the footprint longitudinal axis must be parallel to the
transport direction of the printed-circuit board.
The footprint must incorporate solder thieves at the downstream end.
• For packages with leads on four sides, the footprint must be placed at a 45° angle to
the transport direction of the printed-circuit board. The footprint must incorporate
solder thieves downstream and at the side corners.
During placement and before soldering, the package must be fixed with a droplet of
adhesive. The adhesive can be applied by screen printing, pin transfer or syringe
dispensing. The package can be soldered after the adhesive is cured.
Typical dwell time of the leads in the wave ranges from 3 seconds to 4 seconds at 250 °C
or 265 °C, depending on solder material applied, SnPb or Pb-free respectively.
A mildly-activated flux will eliminate the need for removal of corrosive residues in most
applications.
13.4 Manual soldering
Fix the component by first soldering two diagonally-opposite end leads. Use a low voltage
(24 V or less) soldering iron applied to the flat part of the lead. Contact time must be
limited to 10 seconds at up to 300 °C.
When using a dedicated tool, all other leads can be soldered in one operation within
2 seconds to 5 seconds between 270 °C and 320 °C.
13.5 Package related soldering information
Table 28:
Suitability of surface mount IC packages for wave and reflow soldering methods
Package [1]
Soldering method
Wave
Reflow [2]
BGA, HTSSON..T [3], LBGA, LFBGA, SQFP,
SSOP..T [3], TFBGA, VFBGA, XSON
not suitable
suitable
DHVQFN, HBCC, HBGA, HLQFP, HSO, HSOP,
HSQFP, HSSON, HTQFP, HTSSOP, HVQFN,
HVSON, SMS
not suitable [4]
suitable
PLCC [5], SO, SOJ
suitable
suitable
not
recommended [5] [6]
suitable
SSOP, TSSOP, VSO, VSSOP
not
recommended [7]
suitable
CWQCCN..L [8], PMFP [9], WQCCN..L [8]
not suitable
LQFP, QFP, TQFP
[1]
For more detailed information on the BGA packages refer to the (LF)BGA Application Note (AN01026);
order a copy from your Philips Semiconductors sales office.
[2]
All surface mount (SMD) packages are moisture sensitive. Depending upon the moisture content, the
maximum temperature (with respect to time) and body size of the package, there is a risk that internal or
external package cracks may occur due to vaporization of the moisture in them (the so called popcorn
effect). For details, refer to the Drypack information in the Data Handbook IC26; Integrated Circuit
Packages; Section: Packing Methods.
[3]
These transparent plastic packages are extremely sensitive to reflow soldering conditions and must on no
account be processed through more than one soldering cycle or subjected to infrared reflow soldering with
peak temperature exceeding 217 °C ± 10 °C measured in the atmosphere of the reflow oven. The package
body peak temperature must be kept as low as possible.
SC68C752B_3
Product data sheet
not suitable
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Rev. 03 — 29 November 2005
45 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
[4]
These packages are not suitable for wave soldering. On versions with the heatsink on the bottom side, the
solder cannot penetrate between the printed-circuit board and the heatsink. On versions with the heatsink
on the top side, the solder might be deposited on the heatsink surface.
[5]
If wave soldering is considered, then the package must be placed at a 45° angle to the solder wave
direction. The package footprint must incorporate solder thieves downstream and at the side corners.
[6]
Wave soldering is suitable for LQFP, QFP and TQFP packages with a pitch (e) larger than 0.8 mm; it is
definitely not suitable for packages with a pitch (e) equal to or smaller than 0.65 mm.
[7]
Wave soldering is suitable for SSOP, TSSOP, VSO and VSSOP packages with a pitch (e) equal to or larger
than 0.65 mm; it is definitely not suitable for packages with a pitch (e) equal to or smaller than 0.5 mm.
[8]
Image sensor packages in principle should not be soldered. They are mounted in sockets or delivered
pre-mounted on flex foil. However, the image sensor package can be mounted by the client on a flex foil by
using a hot bar soldering process. The appropriate soldering profile can be provided on request.
[9]
Hot bar soldering or manual soldering is suitable for PMFP packages.
14. Abbreviations
Table 29:
Abbreviations
Acronym
Description
CPU
Central Processing Unit
DMA
Direct Memory Access
FIFO
First In/First Out
LSB
Least Significant Bit
MSB
Most Significant Bit
UART
Universal Asynchronous Receiver and Transmitter
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
46 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
15. Revision history
Table 30:
Revision history
Document ID
Release date
Data sheet status
Change notice
Doc. number
Supersedes
SC68C752B_3
20051129
Product data sheet
-
-
SC68C752B_2
Modifications:
•
added HVQFN32 package option (affects Section 1 “General description”, 3rd paragraph; Table 1
“Ordering information”; Section 5.1 “Pinning”; Section 5.2 “Pin description”; Section 12 “Package
outline”)
•
Section 6.3.3.1 “Assumptions”, second paragraph:
– 1st sentence: changed “RCV FIFO” to “RX FIFO”
– 3rd sentence: changed “0F” to “0Fh”
– 6th sentence: changed “0D” to “0Dh”
•
changed Xoff1, Xoff2, Xon1, Xon2 register names to XOFF1, XOFF2, XON1, XON2, respectively
(Xoff1, Xoff2, Xon1, Xon2 character and word names remain as-is)
•
•
Table 10 “Register map - read/write properties”, Table note 4: changed “xBF” to “BFh”
•
•
•
Table 11 “SC68C752B internal registers”: IER[7:4], FCR[5:4], IIR[5:4], MCR[5:4], LSR[7] bit
descriptions modified (removed “0/” and “0/X”)
Table 24 “Register programming guide” modified: appended “h” to hex numbers
Table 26 “Static characteristics”: changed “f(i)XTAL1: input clock frequency” to “fXTAL1: frequency on
pin XTAL1”
Table 27 “Dynamic characteristics”:
– changed “fXTAL: clock speed” to “fXTAL1: frequency on pin XTAL1”
– changed “t1w, t2w” to “tw1, tw2”
– Table note 3: changed “t3w” to “tw3”
•
Figure 17 “External clock timing” modified:
– “t1w, t2w, t3w” changed to “tw1, tw2, tw3”
– changed “fXTAL” to “fXTAL1” in the equation
SC68C752B_2
20050428
Product data sheet
-
9397 750 14963
SC68C752B_1
SC68C752B_1
20050329
Product data sheet
-
9397 750 13857
-
SC68C752B_3
Product data sheet
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Rev. 03 — 29 November 2005
47 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
16. Data sheet status
Level
Data sheet status [1]
Product status [2] [3]
Definition
I
Objective data
Development
This data sheet contains data from the objective specification for product development. Philips
Semiconductors reserves the right to change the specification in any manner without notice.
II
Preliminary data
Qualification
This data sheet contains data from the preliminary specification. Supplementary data will be published
at a later date. Philips Semiconductors reserves the right to change the specification without notice, in
order to improve the design and supply the best possible product.
III
Product data
Production
This data sheet contains data from the product specification. Philips Semiconductors reserves the
right to make changes at any time in order to improve the design, manufacturing and supply. Relevant
changes will be communicated via a Customer Product/Process Change Notification (CPCN).
[1]
Please consult the most recently issued data sheet before initiating or completing a design.
[2]
The product status of the device(s) described in this data sheet may have changed since this data sheet was published. The latest information is available on the Internet at
URL http://www.semiconductors.philips.com.
[3]
For data sheets describing multiple type numbers, the highest-level product status determines the data sheet status.
17. Definitions
customers using or selling these products for use in such applications do so
at their own risk and agree to fully indemnify Philips Semiconductors for any
damages resulting from such application.
Short-form specification — The data in a short-form specification is
extracted from a full data sheet with the same type number and title. For
detailed information see the relevant data sheet or data handbook.
Right to make changes — Philips Semiconductors reserves the right to
make changes in the products - including circuits, standard cells, and/or
software - described or contained herein in order to improve design and/or
performance. When the product is in full production (status ‘Production’),
relevant changes will be communicated via a Customer Product/Process
Change Notification (CPCN). Philips Semiconductors assumes no
responsibility or liability for the use of any of these products, conveys no
license or title under any patent, copyright, or mask work right to these
products, and makes no representations or warranties that these products are
free from patent, copyright, or mask work right infringement, unless otherwise
specified.
Limiting values definition — Limiting values given are in accordance with
the Absolute Maximum Rating System (IEC 60134). Stress above one or
more of the limiting values may cause permanent damage to the device.
These are stress ratings only and operation of the device at these or at any
other conditions above those given in the Characteristics sections of the
specification is not implied. Exposure to limiting values for extended periods
may affect device reliability.
Application information — Applications that are described herein for any
of these products are for illustrative purposes only. Philips Semiconductors
make no representation or warranty that such applications will be suitable for
the specified use without further testing or modification.
19. Trademarks
18. Disclaimers
Notice — All referenced brands, product names, service names and
trademarks are the property of their respective owners.
Life support — These products are not designed for use in life support
appliances, devices, or systems where malfunction of these products can
reasonably be expected to result in personal injury. Philips Semiconductors
20. Contact information
For additional information, please visit: http://www.semiconductors.philips.com
For sales office addresses, send an email to: [email protected]
SC68C752B_3
Product data sheet
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Rev. 03 — 29 November 2005
48 of 49
SC68C752B
Philips Semiconductors
5 V, 3.3 V and 2.5 V dual UART, 5 Mbit/s (max.), with 64-byte FIFOs
21. 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 . . . . . . . . . . . . . . . . . . . 8
Trigger levels. . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Hardware flow control . . . . . . . . . . . . . . . . . . . . 8
Auto-RTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Auto-CTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Software flow control . . . . . . . . . . . . . . . . . . . 10
Receive flow control . . . . . . . . . . . . . . . . . . . . 11
Transmit flow control . . . . . . . . . . . . . . . . . . . . 11
Software flow control example . . . . . . . . . . . . 12
Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Interrupt mode operation . . . . . . . . . . . . . . . . 15
Polled mode operation . . . . . . . . . . . . . . . . . . 15
DMA operation . . . . . . . . . . . . . . . . . . . . . . . . 16
Single DMA transfers (DMA mode 0/FIFO
disable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Block DMA transfers (DMA mode 1). . . . . . . . 17
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Sleep mode. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Break and time-out conditions . . . . . . . . . . . . 18
Programmable baud rate generator . . . . . . . . 18
Register descriptions . . . . . . . . . . . . . . . . . . . 20
Receiver Holding Register (RHR). . . . . . . . . . 22
Transmit Holding Register (THR) . . . . . . . . . . 22
FIFO Control Register (FCR) . . . . . . . . . . . . . 23
Line Control Register (LCR) . . . . . . . . . . . . . . 24
Line Status Register (LSR) . . . . . . . . . . . . . . . 25
Modem Control Register (MCR) . . . . . . . . . . . 26
Modem Status Register (MSR). . . . . . . . . . . . 27
Interrupt Enable Register (IER) . . . . . . . . . . . 28
Interrupt Identification Register (IIR). . . . . . . . 29
Enhanced Feature Register (EFR) . . . . . . . . . 30
Divisor latches (DLL, DLH) . . . . . . . . . . . . . . . 30
Transmission Control Register (TCR) . . . . . . . 30
Trigger Level Register (TLR). . . . . . . . . . . . . . 31
FIFO ready register. . . . . . . . . . . . . . . . . . . . . 31
8
9
10
11
11.1
12
13
13.1
13.2
13.3
13.4
13.5
14
15
16
17
18
19
20
Programmer’s guide . . . . . . . . . . . . . . . . . . . .
Limiting values . . . . . . . . . . . . . . . . . . . . . . . .
Static characteristics . . . . . . . . . . . . . . . . . . .
Dynamic characteristics . . . . . . . . . . . . . . . . .
Timing diagrams. . . . . . . . . . . . . . . . . . . . . . .
Package outline . . . . . . . . . . . . . . . . . . . . . . . .
Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction to soldering surface mount
packages . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reflow soldering. . . . . . . . . . . . . . . . . . . . . . .
Wave soldering. . . . . . . . . . . . . . . . . . . . . . . .
Manual soldering . . . . . . . . . . . . . . . . . . . . . .
Package related soldering information . . . . . .
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .
Revision history . . . . . . . . . . . . . . . . . . . . . . .
Data sheet status. . . . . . . . . . . . . . . . . . . . . . .
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . .
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contact information . . . . . . . . . . . . . . . . . . . .
32
34
35
36
37
42
44
44
44
44
45
45
46
47
48
48
48
48
48
© Koninklijke Philips Electronics N.V. 2005
All rights are reserved. Reproduction in whole or in part is prohibited without the prior
written consent of the copyright owner. The information presented in this document does
not form part of any quotation or contract, is believed to be accurate and reliable and may
be changed without notice. No liability will be accepted by the publisher for any
consequence of its use. Publication thereof does not convey nor imply any license under
patent- or other industrial or intellectual property rights.
Date of release: 29 November 2005
Document number: SC68C752B_3
Published in The Netherlands