ACT apricot - General; Rs232 C Communications

SERIAL INTERFACE
The corresponding interrupt vector accessed by the CPU
during an interrupt acknowledge cycle associated with the
printer control lines, is the channel B ext/status interrupt
vector (02H), as described in the section on the Write
Registers. The other conditions, which are specified as
being able to generate an external/status interrupt, are not
enabled in channel B.
RS232C COMMUNICATIONS
General
The interface to the RS232C serial link is implemented
by channel A of the SIO, which can be programmed to
operate in either asynchronous or synchronous
communications modes with transmit and receive baud
rates determined either via the Programmable Interval
Timer (TMR), or via the external data communications
equipment.
The clock inputs to the SIO pins TxCA and RxCA, are
used to determine the transmit and receive baud rates for
the RS232C link and are supplied via the data selector. The
select lines to the data selector are provided by two general
purpose outputs (DTRB and R TSB) available through
channel B, which are controlled by software. This allows
the programmer to select:
(a) Different rates for transmit and receive, with the
receive rate determined by the clock output OUTI of
the Interval Timer and the transmit rate, determined
byOUT2.
(b) The same rate for transmit and receive as
determined by OUT2 of the timer.
(c) The same rate for transmit and receive as
determined by the external data communications
equipment (RS232C connector pin, Rx Clock).
Details of the timer and the appropriate programming
values to produce the majority of the commonly used baud
rates are detailed in the TIMER chapter. These values apply
to asynchronous communications only and require channel
A to be programmed in the x16 clock rate mode to achieve