Re: [foxboro] Read back feature of FBM233 with OPC

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.



-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Joachim Leuker
Sent: Friday, October 17, 2008 4:22 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Read back feature of FBM233 with OPC

Hi list,

the output blocks IOUT, ROUT and PAKOUT work with a read back feature 
in the FBM233. At least they do this when used in an OPC interface.

We connected a Siemens S7 PLC to a FBM233. We found out that it is 
possible to manipulate a value of a ROUT or IOUT block from both sides. 
If the value is changed in the PLC, then it also changes in the ROUT 
block.

We also need some bit values to be set in the PLC or in the I/A system. 
We observe a strange behaviour there:
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.

Another strange thing is that if I set IN32, the PAKOUT is frozen and 
no change can be made to it.

I deleted the PAKOUT and put an IOUT to the same OPC address. I made no 
change on the PLC side. Then I could make bit changes on both sides as 
expected and I could also set bit #32.

I/A version is 8.2, the CP is a FCP270.

Is this a configuration error or an error in the PAKOUT block?

Regards,
Joachim Leuker

 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
 
 
 
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
 
foxboro mailing list:             http://www.freelists.org/list/foxboro
to subscribe:         mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe:      mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave

Other related posts: