GE GFK0579B user manual Using Option Modules in a Remote Drop

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Using Option Modules in a Remote Drop

PCMs (Programmable Coprocessor Modules), GDS (Graphics Display Coprocessor Modules), and ADS (Alphanumeric Display Coprocessor Modules) can be located in a remote drop.

These option modules look at the Remote I/O Scanner as though it were a Series 90±70 PLC CPU. They can read and write to any locations in the Remote I/O Scanner's internal %I, %AI, %Q, %AQ, and %R memories, including those portions of memory that are outside the range configured for data transfer with the system host.

The Remote I/O Scanner's %R memory is NOT used for data transferred with the CPU, but it can be freely accessed by a PCM, GDS, or ADS module in the remote drop.

Accessing the Host CPU from Option Modules in a Remote Drop

When used in a remote drop, a PCM, GDS, or ADS module does not have direct access to host CPU memory; to read or write host memory, the data must be transferred through the configured memory area of the Remote I/O Scanner. The area used should not correspond to a physical I/O module; it should correspond to an unused portion of the remote drop I/O map configured for the remote drop.

Extending the I/O map of a remote drop will cause the Genius message to increase in size, and will therefore increase the Genius bus scan time. Gaps may be anywhere in the I/O map, but if they are added to the end, the corresponding I/O references cannot be used for any other purpose by either the host or the Remote I/O Scanner.

Reading Host Data from an Option Module

	HOST		REMOTE I/O
	CPU			SCANNER
		GENIUS
MEMORIES			MEMORIES
		MESSAGE
	% Q			% Q
	% AQ			% AQ

a44887

PCM, GDS

OR ADS

READ

OUTPUT

MODULES

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