
W83977EF/ CTF
PRELIMINARY
Publication Release Date: March 1999
-9 -
Revision A1
1.2 General Purpose I/O Port ,continued
SYMBOL
PIN
I/O
FUNCTION
PANSWIN#
GP23
(P15)
73
IN
t
I/O
12t
Panel Switch input. (CR2B bit 7_6 = 00, default)
General purpose I/O port 2 bit 3. (CR2B bit 7_6 = 01)
Alternate Function from GP23: KBC P15 I/O port
CIRRX
(P16)
GP24
P13
40
IN
t
Consumer infrared receiver input
Alternate Function from GP24: KBC P16 I/O port
General purpose I/O port 2 bit 4 (CR2A bit 5_4 = 01)
KBC P13 I/O port. (CR2A bit 5_4 = 10)
I/O
12t
I/O
12t
IN
ts
SUSC#
(GA20)
39
Suspend C input
Alternate Function from GP25: GATE A20 (KBC P21)
General purpose I/O port 2 bit 5.
GP25
I/O
12
1.3 Serial Port Interface
SYMBOL
PIN
41
48
I/O
IN
t
FUNCTION
CTSA#
CTSB#
Clear To Send is the modem control input.
The function of these pins can be tested by reading Bit 4 of the
handshake status register.
DSRA#
DSRB#
42
49
IN
t
Data Set Ready. An active low signal indicates the modem or
data set is ready to establish a communication link and transfer
data to the UART.
RTSA#
43
I/O
8t
UART A Request To Send. An active low signal informs the
modem or data set that the controller is ready to send data.
HEFRAS
During power-on reset, this pin is pulled down internally and is
defined as HEFRAS, which provides the power-on value for
CR26 bit 6 (HEFRAS). A 4.7 k
is recommended if intending to
pull up. (select 370H as configuration I/O port
′
s address)
RTSB#
50
I/O
8t
UART B Request To Send. An active low signal informs the
modem or data set that the controller is ready to send data.