W83877TF/W83877TG
-8 -
Serial Port Interface, continued
SYMBOL PIN I/O FUNCTION
SOUTB
IRTX1
PIRQMDS
43
I/O
8tc
UART B Serial Output. It is used to transmit serial data out to the
communication link.
During power-on reset, this pin is pulled down internally and is
defined as PIRQMDS to select the IRQ mode. While it is at
Low, IRQ pins can be set to Normal mode or IRQ sharing mode
which decided by CR18. If it is at High, the Serial IRQ mode is
selected. A 4.7 k
Ω is recommended when intending to pull up at
power-on reset.
RTSB
45
I/O
8tc
UART B Request To Send. An active low informs the modem or
data set that the controller is ready to send data.
PGOIQSEL During power-on reset, this pin is pulled down internally and is
defined as PGOIQSEL, which provides the power-on value for
CR16 bit 4 and bit 5 (G0IQSEL & G1IQSEL). While it is at Low,
pins 92 and 96 function as IRQ pins IRQ_B,IRQ_A respectively.
While it is at high, pins 92 and 96 function as General Purpose
I/O pins GIO0,GIO1 respectively. A 4.7 k
Ω is recommended
when intends to pull up at power-on reset.
DTRB
46 I/O
8tc
UART B Data Terminal Ready. An active low informs the modem
or data set that the controller is ready to communicate.
IRTX2 95 OUT
12t
Functions as a InfraRed data transmission line.
IRRX2 94 IN
t
Functions as a InfraRed data receiving line.
4.3 Multi-Mode Parallel Port
The following pins have six functions, which are controlled by bits PRTMOD0, PRTMOD1, and
PRTMOD2 of CR0 and CR9 (refer to section 11.0, Extended Functions).
SYMBOL PIN I/O FUNCTION
BUSY
24 IN
t
PRINTER MODE: BUSY
An active high input indicates that the printer is not ready to
receive data. This pin is pulled high internally. Refer to the
description of the parallel port for the definition of this pin in ECP
and EPP mode.
OD
12
EXTENSION FDD MODE:
MOB2
This pin is for Extension FDD B; the function of this pin is the
same as that of the
MOB pin.
OD
12
EXTENSION 2FDD MODE:
MOB2
This pin is for Extension FDD A and B; the function of this pin is
the same as that of the
MOB pin.
