GE GFK0579B user manual Configuring Extra References, Example

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Configuring Extra References

Normally, there are no extra references configured for the Remote I/O Scanner, since that would consume extra references in the host CPU, making them unavailable for other modules. In addition, extra references add to the Genius bus scan time, so they should be avoided if they are not actually needed.

However, reserving extra references or leaving vacancies at configuration time is a convenient way to prepare for future additions to a remote drop. (If Logicmaster 90±70 is used for configuration, unused references may be placed anywhere in the input message).

Input Data Message with Some Inputs Not Used

a

To CPU

discrete inputs		unused	analog inputs		unused
		discrete			analog
		references			references
	a Configured %I Length '			a Configured %AI Length '
	%I starting reference data			%AI starting reference data

Example

An application has two remote drops, which have been configured as #016 and #017.

Drop 016

%I0001 ± %I0064 %AI0001 ± %AI0008 %Q0001 ± %Q0032 %AQ0001 ± %AQ0008

Drop 017

%I0065 ± %I0128 %AI0009 ± %AI0016 %Q0033 ± %Q0064 %AQ0009 ± %AQ0016

At a later time, it becomes necessary to add a 32±point input module to drop 016. However, in drop 016, there are already enough input modules to use all of the assigned input references (%I0001 ± %I0064). Ideally, the extra modules would be added to remote drop 016 at %I00065, but this is already used as a reference in drop

017. The alternatives at this stage are:

1.Change the map of drop 017 to free up %I0065 ± %I0096.

2.Change the map of drop 016 to start at higher references, such as %I0097 ± %I0160.

It would have been easier to add the module to drop 016 if extra references had been configured originally, or if some vacancies had been allowed.

Drop 016

%I0001 ± %I0096

%AI0001 ± %AI0008 %Q0001 ± %Q0032 %AQ0001 ± %AQ0008

Drop 017

%I0097 ± %I0160

%AI0009 ± %AI0016 %Q0033 ± %Q0064 %AQ0009 ± %AQ0016

Chapter 3 Remote I/O Scanner Operation 49