CONTROL DEVICE
d. Serial Port Driver
This
is
the
most
powerful of all
the
Device Modification
routines,
this
option
allows
the
programmer
to send and
receive characters
and
change
the
SIO (Serial I/O) settings
(Both
Transmit
AND
Recieve BAUD rates, Stop Bits, Parity,
Transmit
Bits, Recieve Bits,
in
addition
to
control
line
status)
DEV-52
COM - From 1 to 16
DA
T - 0 to 255 for character
to
send
COM
= 0:
The
SIO chip is polled to
establish
as
to
wether
the
port
is
ready
to
send
or
receive,
and
the
result
is
returned
in
RET-
o
the
port
is ready,
-1
Not
ready.
COM
= 1:
The
low
byte
of
DATis
transmitted.
cOM=2:
DA
T is ignored,
and
RET
returns
the
ASCII code of
the
character
just
received. If, however, RET
returns-1
(OFFFFH)
then
there
is
no
character
to receive.
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