GE 90-30/20/Micro

4-158 Series 90-30/20/Micro Programmable Controllers Reference Manual – September 1998 GFK-0467K

Example 2:

In the next example, the PLC is shut down when any fault occurs on an I/O module except when the

fault occurs on modules in rack 0, slot 9 and in rack 1, slot 9. If faults occur on these two modules,

the system remains running. The parameter for “table type” is set up on the first sweep. The

contact IO_PRES, when set, indicates that the I/O fault table contains an entry. The PLC CPU sets

the normally open contact in the sweep after the fault logic places a fault in the table. If faults are

placed in the table in two consecutive sweeps, the normally open contact is set for two consecutive

sweeps.

The example uses a parameter block located at %R0600. After the SVCREQ function executes, the

fourth, fifth, and sixth words of the parameter block contain the address of the I/O module that

faulted:

1%R0600

long/short %R0601

reference address %R0602

rack number slot number %R0603

I/O bus no. bus address %R0604

point address %R0605

fault data

In the program, the EQ_INT blocks compare the rack/slot address in the table to hexadecimal

constants. The internal coil %M0007 is turned on when the rack/slot where the fault occurred

meets the criteria specified above. If %M0007 is on, its normally closed contact is off, preventing

the shutdown. Conversely, if %M0007 is off because the fault occurred on a different module, the

normally closed contact is on and the shutdown occurs.