Plc 5000 S:fs

We have a rung of logic with a normally closed S:FS bit in it. The bit is not showing true when online with the PLC, yet the output in series with the bit is true. I am wondering how this bit could be true with the S:FS showing false all the time? I was asked this question and cannot give a good answer as to why it is possible. I have cross referenced the output in the rung and it is not used anywhere else in the ladder. Any input is appreciated. Thanks.

Russ

The bit is not showing true when online with the PLC

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That's quite normal, because S:FS is the First Scan statusbit. It's only true during the first scan of the program. Since you're talking about a normally closed contact, and the S:FS bit is false, I figure this contact stays closed except for the first scan. This way the connected output should be continuously activated.

Maybe it's better to post an image of the rung, because now I'm only basing my conclusion on what I think you're saying.

Kind regards,

I thought about trying to post a pic, but I discovered the answer not long after posting my original post. I didn't have time to post it till now. Under the help tab for the status monitoring bits it does say that the status of those bits is not displayed in the ladder, which explains why the rung can be true while not showing the S:FS bit being true. Thanks.

Russ

An anomaly that you have to live with

The S:FS bit's status is not displayed like other XIO's and XIC's.
It does, however, function as specified.