CLX L62 Wont Go Into Remote-Program Mode

Doing a remote online with a customer on a 1756-L62 (NOT "S"!) in RemoteRun mode. Project is ver16.04



To reset faults the easiest way is put in Program then back to Run.


However multiple tries got a popup that the processor received my command to change but has not. Had to have the customer flip the key switch.



Never encountered this before.

Does anyone know why this would happen?
Is there a fix?

I'll bet you a box of shiny metal donuts that there are MSG instructions in the program that are fanning the trigger.

The Run -> Prog mode transition requires a brief moment of calm in the system buffers and I've definitely seen L6x controllers decline to make that change for that reason.

I think there's a difference between Remote Prog and keyswitch Prog transitions with regard to how they discard or cancel messaging.

Thanks for the quick reply.


This doesn't have any Ethernet MSG commands, but has 8 drives on fiber optic SERCOS and RemoteIO nodes by DeviceNET, so it's probably a similar situation with one, or both, of them.

There goes this week's supply of shiny metal donuts.

The DeviceNet shouldn't affect any buffers; all the I/O connections on that network are handled by the 1756-DNB, which itself has only one simple (but sizable) I/O connection over the backplane.

SERCOS... that probably requires a little more work from the CPU, since it's trying to talk through the SERCOS interface module to the motion controllers.

Or it's something I'm not familiar with. I have experienced similar behavior, but it was generally related to MSG instructions.

Ken Roach said:

There goes this week's supply of shiny metal donuts......

SERCOS... that probably requires a little more work from the CPU, since it's trying to talk through the SERCOS interface module to the motion controllers

Click to expand...

IT was the SERCOS. Couldn't do it online and ended up going to the customers shop.


When I disabled the SERCOS module the PLC could go into RemProg just fine, but back to not-doing-it when I re-enabled SERCOS.


Thanks again for the guidance.