State Industries GFK-0827 Chapter Configuration, Configuring a Hot Standby CPU Redundancy System

Chapter

3

Configuration

This chapter describes how to configure a Series 90-70 PLC system for Hot Standby CPU Redundancy. Several parameters in addition to the normally configured CPU parameters must be configured for the Redundancy CPU 780. A description of all of the parameters for a redundancy system is provided first, followed by an example of a Primary system configuration and a Secondary system configuration.

Configuring a Hot Standby CPU Redundancy System

Asdiscussed previously, when configuring a system for Hot Standby CPU Redundancy, the following parameters require configuration in addition to the CPU configuration parameters that are done for any other CPU78X CPU.

Configuration
Parameter	Description
Fail-wait	The time one PLC will wait on one RCM link for the other
	PLC to respond before faulting that link. The CPU will try
	both links before continuing its scan. Once the RCM links are
	marked as failed, one unit or the other must be power cycled
	to recover them. Range is 60 ms to 400 ms, with the default
	value being 60 ms.
Control Strategy	The control strategy for the current configuration. Config-
	ured as a three-character identifier (GHS for Hot Standby
	CPU Redundancy). The default value is GHS (currently the
	only value that is valid).
Shared I/O References	The references within the control of the Redundancy system;
	limited to total of 20 KBytes for Inputs and 28 Kbytes for Out-
	puts. The references which may be used as shared I/O are
	%I, %Q, %AI, %AQ, %R, and %M. .
Redund Type	Whether the CPU being configured is the Primary or Second-
	ary CPU in the Redundancy system. Redund Type has three
	possible values: PRIMARY, SECONDARY, or SIMPLEX. SIM-
	PLEX indicates a non-redundant system. The default value is
	PRIMARY. SIMPLEX is not a currently supported Redund Type
	for the CPU 780.

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