RSLogix500 Max san display update detail?

OkiePC

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Join Date
Mar 2005
Location
ENE of Nowhere Oklahoma
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Is the maximum scan time display updated by the SLC CPU after every scan?

EDIT: NEVERMIND...OBVIOUSLY WHEN I GO ONLINE AND READ 993 ALREADY IN THE Status file, the SLC keeps it accurate...but...

What would cause an extremely high First scan time?

I have a CPU that has always had a 992 to 996 ms first scan time, and I have studied it closely.

I am still baffled as to why, after finding a First_Scan driven loop and working it completely out of the code, the scan time remains unchanged.

The SLC 5/04 scans at 25-50 ms all other times. EDIT: The watchdog is set for 1000ms. It has never "watchdog" timed out in my nine months here! I have seen it hit 996 after amonth of daily checking. Happens every morning on power up, as well as returning to remomte run mode...every time First_Scan is true, the max reading hits within 8ms of the watchdog, I clear it, and it never again goes above 50 until the next First_Scan.

I suspect it could be I/O or comms related?

There is a pretty heavily populated devicenet control network and around 20 local slots in use. All 30 are enabled.

There are only two nodes on the local DH+ (PV1000 standard, 500ms scan freq. ~300 tags, ~50 alarm bits)

There is also a Net-ENI module connecting it's CH0 to the engineering lab network which could be a factor?

Any ideas AB experts?

I am at home so I can't post the code...
 
Last edited:
From the online help:

Maximum S:22
This word indicates the maximum observed interval between consecutive program cycles. The value (expressed in 10 ms increments when S:33/13=0, or in 1ms increments when S:33/13=1) is the time elapsed in the longest program cycle of the controller. The I/O scan, processor overhead, and communication servicing is not included in this measurement.

So according the online help, I/O and comms are ruled out
 

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