GE GFK0579B user manual Direct Access to I/O by Option Modules, Example

3

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.

HOST

MEMORIES

%Q00001

%Q00256

SENDS

1±256

REMOTE I/O

SCANNER

MEMORIES

%Q00001

%Q00256

%Q00257

%Q00272

%Q00001

%Q00272

OUTPUT

MODULES

a44889

PCM

SENDS

257±272

52 Remote I/O Scanner User's Manual ± July 1992