Remote Technologies RPC-320 - Manual (Page 15)

SERIAL PORTS SECTION 4
Page 4-1 RPC -320
Figure 4-1 Serial port and jumper locations
DESCRIPTION
The RPC -320 has two serial ports that interface to a
printer, terminal, RS-485 network, or other serial
devices. This chapter describes their char acteristics and
how to use th em. Fre quent ref erence s are m ade to
commands listed in the BASIC-52 Programm ing Manual
or RPBASIC-52 Software Supplement in this manua l.
Please refer to these manuals for m ore information about
these comm ands.
Serial por ts are num bered C OM 0 and CO M1. COM 0 is
RS232 only and is used for progr am deve lopment.
During r un time, it can be used for other functions.
COM 1 is a general purpose port and is jumperable for
RS-232 or RS-422/485.
Each port has a 256 character interr upt driven input and
output buffer. This allows sending characters without
slowing down program execution. How ever, if the
PRIN T buffer fills, pr ogram execution is susp ended until
all PRINT char acters are in the buffer. Both ports have
a 256 character input buffer. When mor e than 256
characters are r eceived, excess ones are ignored.
CON FIG BAU D controls baud rate and RS-232/485
mode (CO M1 only).
ON C OM $ is useful whe n data is sent in pac kets. This
multitasking command branches to a BASIC subroutine
when a sp ecific char acter or number of chara cters is
received.
Another useful function is STR. Strings can be
formatted, analyzed for length and content. When used
in conjunction with ON COM $, networ king over RS-485
is much easier than with the original BASIC-52.
COM0 SERIAL PORT
This port uses a VTC-9F serial cable to connect external
serial dev ices to the por t. T he cable con sists of a 10 pin
IDC connector wired one-to-one to a DB-9 connector.
Line 10 is sim ply cut off. The pin ou t is designed so it
plugs directly into the 9 pin serial port connector on a
P C .
CTS is a output and is set to high on power up.
Norm ally, this tells the other device to send data. The
CTS line is set high or low to hold off communication.
The sending device must have a RTS input. L ine 400
sets CTS high and 500 sets it low, or to hold off.
400 LINEB 5,0,(LINEB(5,0) .AND. 247)
500 LINEB 5,0,(LINEB(5,0) .OR. 8)
COM 0 is normally used for program ming. D uring run
time it ma y be used as a genera l purpose serial por t.
W h e n u s ed f or p r og r a m mi ng o r w i th th e IN P U T
s ta t em e n t, i t wi ll ac c ep t A S C II c ha r a ct e r v a lu e s f r om 0
to 127. When used with the GET function, it will return
ASCII values from 0 to 255.
COM1 SERIAL PORT
COM 1 is either an RS-232 or RS-422/ 485 port. A
VTC -9F serial cable, descr ibed above, is used for RS-
232 level communications. RS-485 is from screw
terminals. COM 1 has 2 hardw are handshaking lines,
CTS and RT S.
RTS is an input to the car d. W hen RT S to the car d is
low, it usually indicates the sender does not want any
data sent to it. The status of this port is read by the
LINEB statement. The example below retur ns a status
of the RTS line:
100 B = LINEB(5,1) .AND. 32
If B = 32, the sender is not requesting information and
nothing further should be printed.
The CT S line may be set high or low to hold off
comm unication from a se nding device. The sender must
recognize the CTS line. Line 400 sets CTS high and 500
sets it low, or to hold off.