Schneider Electric 840 USE 106 0 manual Verifying Health of a Hot Standby System, Health Messages

Maintenance

Verifying Health of a Hot Standby System

Health Messages	The Hot Standby modules exchange a health message approximately every 10 ms.
	If the Primary has an error, the Standby is notified and assumes the Primary role. If
	the Standby has an error, the Primary continues to operate as a standalone.
	The RIO head processors also verify communication with one another periodically.
Automatic
	The system automatically performs two kinds of confidence tests on the Hot Standby
Confidence	modules:
Tests
	lStartup tests
	Run time tests
Startup Tests
	The system performs four startup tests:

Prom checksum

RAM data test

lRAM address test Dual port RAM test

If the module fails any of these tests, it remains offline and does not communicate with the other Hot Standby module. To retest the system, the power must be turned off and on again.

Run Time Tests These tests are performed whenever the Ready indicator is on. They are executed in small groups to prevent delays in scan time.

The system performs three kinds of run time confidence tests:

Prom checksum

lRAM data test RAM address test

180 840 USE 106 00 January 2003