Applies To:
  • CitectSCADA

I have a customer with B&R (Bernecker And Rainer) Black Line PLCs using the CP60 processor and he has an interest in connecting into his existing Citect system. Does anyone have experience in doing this sort of thing with the B&R PLC and if so, what does it take to get this working? 

We had an application some eons ago with a B&R CP40, using Modbus protocol in RTU mode. It works, but it's painful: a couple of things to note:

1. B&R registers are 8 bit, whereas Modbus addresses 16 bit registers. This causes a problem in reading and writing blocks, eg reading R0-R9 would be set up as Modbus addresses, say 40001-40005. ie 40001 = R0/R1, 40002 = R2/R3, etc.

This sounds ok, but Citect writes only on register at a time, therefore writing to Modbus address 40002, you would expect the write to go to R2/R3, but it doesn't, it goes to R1/R2 !!!!! - problem at the B&R end.

2. To get round this problem you need to set the addresses outside of the blocking constant size (typically 48), therefore Citect would only read one word at a time, and hence slowing comms down by a factor of several squillion, compared to blocked reads.

Eg Tag_1 = 40001, Tag_2 = 40051, etc.

This problem also applies to just reads, since Citect will start a block read at the first address it finds on a page (eg if the lowest addressed tag is 30001). You may want to experiment with trend tags, but only if they are all likely to be read at the same time.

There's no problem on reading bits, just map the I/O into flags (F0+) and it works OK. Bit reads and writes are no problem (F0 = 00001 or 10001). So just watch out for Integers . . . . and forget Reals !!

Possibly the best way is to use the ArcNET communications; this was checked a couple years ago, and seems OK, but ArcNET is expensive. . .