Radio Shack TRS-80 Model II Reference Manual page 248

Model II TRSDOS
RS232C
Initialize RS-232C Channel
(Function Code 55)
This routine sets up or disables either channel A or B. Before using it, the
appropriate channel should be connected to the modem or other equipment.
This routine sets the standard
RS-232C
parameters, and defines a pair of supervisor
calls for 110 to the specified channel. When you initialize Channel A,
SYC'S
96,97
and 100 are defined; when you initialize Channel B,
SYC'S
98,99 and 101 are
defined. See
ARCY , ATX, BRCY, BTX, ACTRL
and
BCTRL.
Before re-initializing a channel,
always
turn it off. You may not turn off channel A
when
HOST
is active.
Entry Conditions
(HL)
=
Parameter list described below
B
=
Function switch:
If B is not equal to zero then tum on the channel and define I/O
SVC's
for that channel
If B is equal to zero then tum off the channel and delete I/O
SVC's
for that channel. In this case only the first byte in the
parameter list ("A" or "B") is used.
A
=
55
Parameter List
This six-byte list includes the necessary
RS-232C
parameters:
CHANNEL BAUD WORD PARITY STOP END LIST
RATE LENGTH BITS MARKER
CHANNEL
is an
ASCII
"A" for channel A, or "B" for channel B.
BAUD RATE
is a binary value from 1 to 8:
1 for 110 baud
2 for 150 baud
3 for 300 baud
4 for 600 baud
5 for 1200 baud
6 for 2400 baud
7 for 4800 baud
8 for 9600 baud
WORD LENGTH
is a binary value from 5 to 8:
5 for 5-bit words
6 for 6-bit words
7 for 7-bit words
8 for 8-bit words
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