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Remote I/O Scanner User’s Manual – July 199252
Direct Access to I/O by Option Modules
A PCM, GDS, or ADS module in the remote drop can read inputs from, and send
outputs to, any I/O module in the drop. This may include modules which do not
communicate with the system host at all.
It is possible to place I/O modules in a remote drop, and use Logicmaster 90 to assign
them references outside the range configured for the Remote I/O Scanner. Although
the host CPU would not be aware of such modules, the Remote I/O Scanner would
include them in its regular I/O scan. By reading or writing the assigned references in
the Remote I/O Scanner’s internal memory, an option module could independently
monitor or control I/O modules in the remote drop.
Example
A Remote I/O Scanner might be configured to receive from the CPU 256 outputs, from
%Q0001 to %Q0256, while output modules in the remote drop were configured using
Logicmaster 90 to use outputs %Q0001 to %Q0272. Although the module assigned to
references %Q00257 to %Q00272 would never receive outputs from the CPU, it could
be controlled by any PCM, GDS or ADS module in the remote drop. To control the
module, a PCM, GDS, or ADS module would send data to the corresponding %Q
outputs in the Remote I/O Scanner’s internal memory.
OUTPUT
MODULES
%Q00257
HOST
SENDS
1–256
MEMORIES
REMOTE I/O
SCANNER
a44889
PCM
%Q00001
%Q00256
MEMORIES
%Q00001
%Q00256
%Q00272
%Q00001
%Q00272
SENDS
257–272