CLX L81/L83s - operand invalid for SSV WallClockTime

[dscish]

Found a minor error generated on a rung which holds an SSV instruction for WallClockTime. Parameters for the instruction are as follows:

Set System Value
Class Name: WALLCLOCKTIME
Instance Name: [blank]
Attribute Name: DateTime
Source: PLC_WCT[0] where PLC_WCT is a DINT[7]

Minor error logged is as follows:

(Type 04) Program Fault
(Code 06) GSV / SSV operand invalid

Routine with the above SSV validates fine without errors or warnings. This is existing code from 10 years ago which went from firmware revision 16 to 30, from what I gather this code was used to synchronise controllers, but now time sync is done via Ethernet modules and the time sync functionality on those, so this is not really required. Could that be the reason for the error? or was SSV for WallClockTime simply scraped in firmware rev 30?

Cheers,
Tom

 

[Ken Roach]

now time sync is done via Ethernet modules and the time sync functionality

Exactly correct.

Because the controller is getting its time from elsewhere, you can't alter the onboard timeclock without metaphorically sticking a spanner in the works.

The SSV instruction will return an "invalid operand" error if you put an out-of-range value, like putting 25 in the Hour element. If you enable Time Synchronization, then it considers all operands invalid and returns the same error code.

You can confidently remove that code from your controller, or leave behind a rung comment explaining how and why the function works differently with your time sync source.

 

[dscish]

As usual Ken, you're an absolute legend, thank you kindly for the quick reply and info!

Cheers,
Tom

 

[dscish]

If you enable Time Synchronization, then it considers all operands invalid and returns the same error code

One additional question Ken (or anyone else for that matter), are all SSV/WALLCLOCKTIME instructions not allowed if Time Sync is enabled, regardless of whether a PLC is a grand master clock or not?

I'm asking as I have a PLC which acts as grand master clock and "offers" its time to 9 other PLC (which also have time sync enabled). The main issue I'm facing is that this grand master clock PLC gets its time from another subsystem (via serial comms) and needs to use an SSV instruction to set its own time and sync to that subsystem. Now of course with time sync enabled, that is not possible, which effectively means that those 9 PLCs do sync up to that single PLC, but the time on that PLC isn't necessarily correct (and I do agree it shouldn't really be called the grand master clock if it then has to sync up further upstream).

Regards,
Tom

 

[BachPhi]

You can try :

Serial Comm Buffer > 0 then Disable TimeSync.

set SSV

Serial Comm Buffer = 0 then Re-Enable TimeSync.