Re: [foxboro] Read back feature of FBM233 with OPC
- From: Joachim Leuker <leuker@xxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Sat, 18 Oct 2008 00:30:07 +0200
Am 17.10.2008 um 22:37 schrieb Ron Schafer:
> I too have seen some strange behavior with pakout blocks. Im using
> 233's
> to a modicon plc(s) and seems we get some random toggling of bits. A
> simple toggle on any bit on the DCS end seems to fix it. Perhaps it is
> timing or something like your seeing. Since its intermittent its been a
> real bear to troubleshoot.
>
>> 1) We set bit IN1 in the PAKOUT
>> 2) We set bit #2 in the PLC, and the bit is also set in the PAKOUT. It
>> looks the same as bit #1 in the detail display.
>> 3) Then we set IN3 in the PAKOUT. The change made earlier to bit #2 is
>> reversed and only IN1 and IN3 are set.
>
> I would expect this behavior since the packout pakcin parameter doesn't
> know about the bit you toggle in the plc. So the next time you change a
> bit to the same pakout block, it retransmits the entire block (which it
> thinks in2 should be off-pakcin.b2) to the plc and the readback value
> will display it as off.
> Basically, you forced the bit on in the plc, the readback value reads
> the force, but the next transmit overrides the force turning it back
> off.
>
If the bit is toggled in the PLC, I can see this change in the detail
display. It shows that the parameter in2 is set in my step 2. It also
shows that bit #2 of the "PAKCO" output parameter of the block is set.
So both parameters know about the change.
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