ACT apricot - Page 132

SERIAL INTERFACE
The serial channel between the Keyboard and the System
Unit supports full duplex asynchronous communications at
a fixed baud rate, and also carries the hardware system reset
control signal
which is multiplexed onto the Data in line
from the Keyboard.
The RS232C channel can be programmed to operate in
either asynchronous or synchronous modes, with transmit
and receive baud rates determined either via the
Programmable Interval Timer (TMR), or via the external
data
communications equipment.
The RS232C interface is able to support:
(a) Asynchronous communications with 5, 6, 7 or 8 bits
per character and various choices of stop bits and parity
sense.
(b) Bit oriented synchronous communications, such as
SDLC
and HDLC.
(c) Byte oriented synchronous communications, such
as Monosync and Bisync.
A
further function of the Serial Interface is to provide the
Parallel Interface on the System Board with a means of
generating
interrupt vectors, which act as pointers to
associated
interrupt service routines. This is achieved by
utilising spare facilities in the keyboard serial channel.