ControlLogix and PLC5 Remote I/O Rack

[curlyandshemp]

But the 1771-QRD was way before the Contrologix. The BTR/BTW do not work the same as the MSG instruction. I think in your case the 1771-QRD responds to the first READ BTR then stops waiting for a TRUE-FALSE-TRUE transition for the next read. Try putting the AND NOT 1771QRD_READ.EN to enable the MSG intsruction in your case

 

[tgoulding]

But the 1771-QRD was way before the Contrologix. The BTR/BTW do not work the same as the MSG instruction. I think in your case the 1771-QRD responds to the first READ BTR then stops waiting for a TRUE-FALSE-TRUE transition for the next read. Try putting the AND NOT 1771QRD_READ.EN to enable the MSG intsruction in your case

This was the way the message was formatted for the PLC5 in the QRD user manual, I just copied the example. The same way I would have done for the analog card?

I assume you mean putting the 'AND NOT 1771QRD_READ.EN' to enable the read message instruction.

 

[curlyandshemp]

This was the way the message was formatted for the PLC5 in the QRD user manual, I just copied the example. The same way I would have done for the analog card?

I assume you mean putting the 'AND NOT 1771QRD_READ.EN' to enable the read message instruction.

Yes, give that a try.

Now I recall why I like to define all modules in the I/O tree. I like to create an ALIAS tag to an Input or Output module. If I create an ALIAS to an Output module on rack 2 group 0, from then on it is called O20, then in the program for O20.0 i can reference O20.0 rather than "rack_2:O.Data[0].0"

 

[tgoulding]

A few things for me to try, thanks for that.

 

[Ken Roach]

Those old manuals are useful, but they should not be taken as gospel. I don't have one of the 1771-QRD manuals (those are very, very uncommon modules) but I'll bet that if they show an unconditioned BTR or BTW instruction that they have the instruction set for "Continuous Mode". This was a PLC-5 feature that isn't present in the ControlLogix.

The traditional way to trigger a Message repeatedly is to precede it with an " XIO MessageControl.EN " instruction. If you have two messages to alternate, put both .EN bits and XIO instructions as conditions for both messages.

Does this module need constant writes and reads, or does it need an initialization write and then constant reads ?

I generally prefer to execute messages on time basis instead of alternating them as fast as they'll go.

 

[tgoulding]

Hi Ken

Thanks for reply. Appreciate that the traditional way to trigger a Message repeatedly is to precede it with an " XIO MessageControl.EN " However like you I was also unfamiliar with this card and the examples in the user manual were my only point of reference.

In answer to you question, no it doesn't need a constant write or an initialization write. The word that is written deals with totalizer rest and overflow flag bits. It does require constant reads as the 9 words coming back contain rate values, total values and response code/error code for the four channels.

 

[tgoulding]

PLC5 and ASB have no idea if module is installed or not and really don't care about them. So adding modules is useless.QUOTE]

Just to come back on this problem. I was in error when I originally posted that I had only listed the Digitals in the I/O tree. I had actually listed the rack 1 ASB and both the Analog Card (Group 0) and QRD card (group 2), none were showing any warnings in the I/O tree. The problem has since been solved by using the XIO .en bits for read and write messages on both read and write mesages. All is well that ends well. Again thanks for your help.

 

[tgoulding]

But the 1771-QRD was way before the Contrologix. The BTR/BTW do not work the same as the MSG instruction. I think in your case the 1771-QRD responds to the first READ BTR then stops waiting for a TRUE-FALSE-TRUE transition for the next read. Try putting the AND NOT 1771QRD_READ.EN to enable the MSG intsruction in your case

Just to come back on this problem. I was in error when I originally posted that I had only listed the Digitals in the I/O tree. I had actually listed the rack 1 ASB and both the Analog Card (Group 0) and QRD card (group 2), none were showing any warnings in the I/O tree.
The problem has since been solved by using the XIO .en bits for read and write messages (as suggested by you and others) on both read and write mesages. All is well that ends well. Again thanks for your help.

 

[tgoulding]

The traditional way to trigger a Message repeatedly is to precede it with an " XIO MessageControl.EN " instruction. If you have two messages to alternate, put both .EN bits and XIO instructions as conditions for both messages.[\QUOTE]


This problem has been solved by using the XIO .en bits for read and write messages (as suggested by you and others) on both read and write mesages. All is well that ends well. Again thanks