Old school-Modicon 984-685E Hot Stand-By Question

[rivas1464]

I've got an existing Modicon 984-684E system set-up in a hot stand-by configuration. The customer tried to add a couple of new I/O cards with disasterous results. The system was down for a half hour before they could get it back up and the new I/O cards were not active. I haven't used a PLC like that in over 10 years and I've forgotten how to deal with an I/O configuration change on a hot stand-by system with minimal impact. I know how to download a new program with no problem but I'm unsure about I/O config changes.

I'm guessing you need to stop the secondary PLC, make the I/O config changes, then kill the primary and then bring up the secondary with the primary off line. Then make the same changes to the primary and bring it back up on-line.

Any help?

Thanks.

 

[Jim Dungar]

I agree.

For new I/O to be recognized, the processor Traffic Cop needs to be edited. This requires a "re-configuration" of the processor so it must be done Off-Line.

Caution: an error might be generated when your primary processor ladder logic is not equal to your stand-by processor logic. The processors don't really care however some component in your system may be monitoring the Hot-Standby (HSBY) status register bit 12