B–10
RLL Communications Programs
Data Communications Module, 2nd Edition, 2/03
If you’re using multiple reads and writes in the
RLL program, the routines need to be
interlocked to be certain that all the routines
are executed. If the interlocks are not used,
then the CPU will only execute the first routine.
This is because the D2–DCM can only handle
one transaction at a time.
In the example, once the RX instruction is
executed, C0 is set. When the D2–DCM has
finished the communication task, the second
routine is executed and C0 is reset.
If you’re using RLL
PLUS
, you can just put each
routine in a separate program stage to ensure
proper execution. In most all cases, RLL
PLUS
can be a more efficient way to create an
automation program.
The
Direct
NET manual provides a master /
slave example with both RLL and RLL
PLUS
program descriptions.
SP124
LD
K201
LD
K3
LDA
O40600
RX
Y0
C0
C0
Set
Interlocking Relay
SP124
LD
K201
LD
K3
LDA
O40400
WX
Y0
C0
C0
RST
Interlocking Relay
Multiple Read and
Write Interlocks
Содержание D2-DCM
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