SLC 500 5/05

[mosheen 0]

Hello everyone. I have a 5/05 programmed to use the S:4/5 bit to pulse an alarm buzzer. The problem is that the Free-Running Clock is not running at all. The S:4 register stays at 000-0000-0000-0000 at all times. It doesn't matter what mode the processor is in. I can toggle bits, and they reset to zero when the processor is switched to PRG, but it just doesn't count in Run or Remote. Am I missing something obvious? Thanks for your time.

[Bob O 8]

Welcome! Can you post your code? If not, is the routine the alarm buzzer being scanned meaning do you have a JSR to the Sub? HTH

[Ken Roach 194]

The RA Knowledgebase (Article ID 61442, TechConnect Required) suggests that it's possible for this effect to come from a damaged controller or from a corrupted project file. Try loading an empty project file into the controller to see if S:4 runs. If it does, then try to re-compile your project by saving it as a *.ACH file then re-opening that file. If the S:4 clock doesn't run with an empty project file loaded, then the controller is damaged.

[mosheen 0]

Thanks for the replies. Sparky: The alarm fires fine if I set the s:4/5 bit high. It's basically: [Trigger Alarm]---------[s:4/5 to pulse alarm]---------------------------------(O:1/12 - Alarm power out) Propeller Head: I will look into that. i know it's not the processor as it's on two machines. We installed a OEM update last month and the fault was not discovered then, and I'm now trying to track it down. It is connected to two panelview's so I'll also check for the unlikely event that the S register is being zeroed by them. My main concern was that I was missing a configuration bit, or some sort of stop command I didn't know about. I'll look into it some more today and let you know what I find. Thanks!

[Ken Roach 194]

This is a very unusual malfunction; I have worked with hundreds of SLC-500 controllers and never encountered it. You are right to check for something writing over the S:4 register, though I would be surprised if anything but ladder logic could do so fast enough to not be apparent. You can actually write any value to S:4 and it will begin counting from that value. It's a quick and dirty way to do "microseconds elapsed" logic, by writing a zero to S:4 when an interval starts, then copying the value out when the interval ends. Obviously that messes up any other logic dependent on the S:4 register, but it's a tool in the box.

[mosheen 0]

Myself. That's why I'm stumped. I was thinking the S:4 could be reset to 0 all the time, but the likelihood of that happening so fast that it would always show 0 is very unlikely. My ladders in both the PV and the 500 only show XIC commands to any of the S4 blocks.

[OkiePC 14]

Seems I recall this happening to me when there was an invalid month or year or something like that in the real time clock... EDIT: No, I remember it was a corrupted application that caused my issue and I fixed it by saving it as an archive and then reopening it. Edited 10 Jan 2013 by OkiePC

[mosheen 0]

Sounds like a plan, I will give it shot.

[mosheen 0]

Well, the unpack didn't work. I'm going to contact the OEM rep and have them verify their code. The processor FRC runs fine with an earlier revision. Thanks again everyone.