5

Operation of the Discrete Output Autotest

The PLC that is presently the autotest master informs the other PLCs (if any) which autotest group it is about to test.

All PLCs read the diagnostic status of all blocks in the group to be tested, and will ignore any subsequent faults that may occur in that group.

The autotest master PLC reads the current output state and force state for each circuit in the output group.

Then, the autotest master pulse-tests the blocks in the output group (details of pulse test operation are explained on page 5-10). The test sequence is described below.

1.For the 4-block output group, the autotest master overrides the normally deenergized outputs on block C to ON.

A

Load

Block C normally deenergized C outputs overridden ON

B

D

2.The autotest master pulse-tests block B. Any faults on block B are noted.

A

Load

Block C outputs still

C

overridden ON

 

BBlock B Pulse-tested

D

3.If any outputs on block B configured as normally-energized logged a Failed Switch when pulsed, the master overrides them to OFF.

A

Load

Normally-energized

Boutputs with Failed Switch are overridden OFF.

Block C outputs still

C

overridden ON

 

D

5-8

GeniustModular Redundancy Flexible Triple Modular Redundant (TMR) System

GFK-0787B

 

User's Manual ±March 1995

 

Page 68
Image 68
GE GFK-0787B user manual Operation of the Discrete Output Autotest