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PLC Communications
5-2
386/ATM Coprocessor User Manual
5.1
Overview
An application program in the 386/ATM communicates with the PLC using
the PCCOMM service of the MS-DOS character device driver 386ATM.EXE.
Figure 5-1 shows the sequence of communication used.
The application program writes (using any language which uses MS-DOS character I/O facilities)
a command string to PCCOMM.
PCCOMM interprets the command string, performs error checking, and passes valid commands
to the PLC.
The PLC performs the requested command and returns any data requested.
The application program reads a string returning the status and data of the request.
Figure 5-1
Communication Sequence
The CONFIG.SYS file must contain the correct instructions for loading the
386ATM driver during the module’s boot procedure in order to activate the
PCCOMM service. The INSTALL batch file included as part of the
installation procedure makes these modifications automatically. Make sure
that the following lines are included in a file called CONFIG.SYS
in the root
directory.
FILES 30
BUFFERS 20
device=C:\HIMEM.SYS
device=C:\386ATM.EXE
See the example CONFIG.SYS file on page 3-7 if you want to load the ATM
driver in high memory.
Communicating
with the PLC
Verifying the
CONFIG.SYS File in
your Root Directory
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