Philips Semiconductors
Product data
SCC2681
Dual asynchronous receiver/transmitter (DUART)
2004 Apr 06
4
SYMBOL
NAME AND FUNCTION
TYPE
PIN
SYMBOL
NAME AND FUNCTION
TYPE
DIP28
DIP40
PLCC44
X2
37
33
24
I
Crystal 2: Crystal connection. See Figure 7. If a crystal is not used it is best to keep
this pin not connected although it must not be grounded.
RxDA
35
31
22
I
Channel A Receiver Serial Data Input: The least significant bit is received first. “Mark”
is HIGH, “space” is LOW.
RxDB
11
10
7
I
Channel B Receive Serial Data Input: The least significant bit is received first. “Mark”
is HIGH, “space” is LOW.
TxDA
33
30
21
O
Channel A Transmitter Serial Data Output: The least significant bit is transmitted
first. This output is held in the “mark” condition when the transmitter is disabled, idle or
when operating in local loopback mode. “Mark” is HIGH, “space” is LOW.
TxDB
13
11
8
O
Channel B Transmitter Serial Data Output: The least significant bit is transmitted
first. This output is held in the “mark” condition when the transmitter is disabled, idle or
when operating in local loopback mode. “Mark” is HIGH, “space” is LOW.
OP0
32
29
20
O
Output 0: General purpose output or Channel A request to send (RTSAN,
active-LOW). Can be deactivated automatically on receive or transmit.
OP1
14
12
9
O
Output 1: General purpose output or Channel B request to send (RTSBN,
active-LOW). Can be deactivated automatically on receive or transmit.
OP2
31
28
–
O
Output 2: General purpose output or Channel A transmitter 1
× or 16× clock output, or
Channel A receiver 1
× clock output.
OP3
15
13
–
O
Output 3: General purpose output or open-drain, active-LOW counter/timer interrupt
output or Channel B transmitter 1
× clock output, or Channel B receiver 1× clock output.
OP4
30
27
–
O
Output 4: General purpose output or Channel A open-drain, active-LOW,
RxRDYA/FFULLA interrupt output.
OP5
16
14
–
O
Output 5: General purpose output or Channel B open-drain, active-LOW,
RxRDYB/FFULLB interrupt output.
OP6
29
26
–
O
Output 6: General purpose output or Channel A open-drain, active-LOW, TxRDYA
interrupt output.
OP7
17
15
–
O
Output 7: General purpose output or Channel B open-drain, active-LOW, TxRDYB
interrupt output.
IP0
8
7
–
I
Input 0: General purpose input or Channel A clear to send active-LOW input (CTSAN).
Pin has an internal VCC pull-up device supplying 1 to 4 A of current.
IP1
5
4
–
I
Input 1: General purpose input or Channel B clear to send active-LOW input (CTSBN).
Pin has an internal VCC pull-up device supplying 1 to 4 A of current.
IP2
40
36
27
I
Input 2: General purpose input or counter/timer external clock input. Pin has an internal
VCC pull-up device supplying 1 to 4 A of current.
IP3
3
2
–
I
Input 3: General purpose input or Channel A transmitter external clock input (TxCA).
When the external clock is used by the transmitter, the transmitted data is clocked on
the falling edge of the clock. Pin has an internal VCC pull-up device supplying 1 to 4 A
of current.
IP4
43
39
–
I
Input 4: General purpose input or Channel A receiver external clock input (RxCA).
When the external clock is used by the receiver, the received data is sampled on the
rising edge of the clock. Pin has an internal VCC pull-up device supplying 1 to 4 A of
current.
IP5
42
38
–
I
Input 5: General purpose input or Channel B transmitter external clock input (TxCB).
When the external clock is used by the transmitter, the transmitted data is clocked on
the falling edge of the clock. Pin has an internal VCC pull-up device supplying 1 to 4 A
of current.
IP6
41
37
–
I
Input 6: General purpose input or Channel B receiver external clock input (RxCB).
When the external clock is used by the receiver, the received data is sampled on the
rising edge of the clock. Pin has an internal VCC pull-up device supplying 1 to 4 A of
current.
VCC
44
40
28
I
Power Supply: +5V supply input.
GND
22
20
14
I
Ground
n.c.
1, 12,
34, 23
–
Not connected.