fanuc 90-30 cpu 352 time clock

[Arknsparc]

We recently purchased a IC693CPU352 module and it appears the internal time clock is static. I can set the time and date but once set it does not progress. The time and date remain either the synchronized time or the manually set time and date indefinitely. Our program which utilizes this internal clock time does not function. Is there an on off setting, internal battery, or a configuration change I can make to troubleshoot this?

 

[Steve Bailey]

The data sheet for the CPU module calls it a "battery-backed clock", but I don't know if its a separate battery for the clock or if its the same battery that saves the RAM memory. At any rate, if it doesn't keep time even when the CPU is powered, I'd suspect the RTC clock chip has failed.
A long shot for troubleshooting would be the SVC_REQ function that reads the clock. The same function is used to set and read the clock. The value in the first %R register of the parameter block associated with the SVC_REQ determines whether to read or write. A value of zero commands read; a value of 1 commands write. If that parameter got inadvertently changed, it could explain what you're seeing as the ladder logic would be constantly writing to the clock.

 

[Arknsparc]

The data sheet for the CPU module calls it a "battery-backed clock", but I don't know if its a separate battery for the clock or if its the same battery that saves the RAM memory. At any rate, if it doesn't keep time even when the CPU is powered, I'd suspect the RTC clock chip has failed.
A long shot for troubleshooting would be the SVC_REQ function that reads the clock. The same function is used to set and read the clock. The value in the first %R register of the parameter block associated with the SVC_REQ determines whether to read or write. A value of zero commands read; a value of 1 commands write. If that parameter got inadvertently changed, it could explain what you're seeing as the ladder logic would be constantly writing to the clock.

Thanks Steve, our really good PLC guy was looking at this and agreed as to how its programmed and should work. He verified the logic and what it is supposed to be doing, and not. He's been doing this for thirty years and has never seen a clock fail to run like this. When I return to the site I am going to pull the unit, try a backup for luck and take a look at the internals of the CPU for a battery. My backup unit has what appears to be a battery connector but no battery, or maybe a battery tucked into the middle of the card. Thank you very much. Appreciate your response.

 

[Steve Bailey]

The normal battery backup of the RAM memory utilizes the battery installed on the power supply module. The battery connection on the CPU module allows you to connect a battery and remove the CPU from the baseplate, which would otherwise disconnect it from the battery.
I looked at my CPU351 which is of the same vintage as your CPU352 and I don't see anything that looks like or is labeled as a battery. There is a large capacitor (labeled C11) which will maintain RAM for perhaps a half hour, but nothing like the battery on a laptop mother board for maintaining RTC memory.

 

[Arknsparc]

Interesting, although I'm not sure what the logic behind the battery connection on the CPU is, as access is only available if you remove the front cover, which requires removing the module. But you've saved me from opening the one CPU further by letting me know it's a capacitor and not a funky looking battery.

What started all this was having to replace the power supply due to a faulty comm link and subsequently losing the configuration. What we uploaded prior to installing the new power supply, would not download properly, and we were led to believe the CPU failed. There were 300+ conflicting address errors. Turns out our recent upload wouldn't download. We had to reach out to our vendor for their version of our configuration which is now currently working, except for the clock.

If you follow all that, my intention having spoken to you is to try the original CPU, whose clock was working and failure is unconfirmed. At the end of the day I am hoping to determine the original CPU's operational status and possibly return the recently purchased CPU module with the bad clock.

 

[Steve Bailey]

I'm not sure what the logic behind the battery connection on the CPU is

Nothing more than a convenience. It allows to keep a backup CPU on the shelf without having to install it in a rack with a power supply. Also allows you to transport a CPU module with a program to another machine or to someone who can evaluate it. Or for a situation where you want to try something new with a different program in a different CPU. It gives you the means to put things back the way they were after the trial.