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Author Topic: Set time for SP4 bit.  (Read 1229 times)

MVetrano

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Set time for SP4 bit.
« on: June 15, 2021, 08:54:24 AM »
I was upgrading the HMI on an old machine when I ran across this issue. Lines 47 and 48 of the code toggles between two messages on the bottom line display of an Optimate 1500 HMI. The messages change about every 3 seconds.
When I monitor the status of the SP4 bit, it changes state about every 3 seconds. This is a one second bit that is supposed to change state every 500ms. How is it possible to make it change every 3 seconds?
The PLC is a DL205 with a DL240 CPU as a master and another 240 as a slave.

BobO

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Re: Set time for SP4 bit.
« Reply #1 on: June 15, 2021, 09:21:13 AM »
I was upgrading the HMI on an old machine when I ran across this issue. Lines 47 and 48 of the code toggles between two messages on the bottom line display of an Optimate 1500 HMI. The messages change about every 3 seconds.
When I monitor the status of the SP4 bit, it changes state about every 3 seconds. This is a one second bit that is supposed to change state every 500ms. How is it possible to make it change every 3 seconds?
The PLC is a DL205 with a DL240 CPU as a master and another 240 as a slave.

Probably aliasing due to a relatively low comm rate. If you sampled at exactly 1 second, and caught it on all of the time, it would look like it never changed. If you sampled at 800-900ms or 1.1-1.2s, it would look like it was toggling at a lower rate than the stated 1 second.
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