AB PLC5 - Two BTR/BTW Blocks


Thread Starter

RK Sastry

We have a MCM 3100 module (Prosoft) in a PLC5/80E rack which fetches data from four Modbus RTU Slaves. We are infact replacing four '7 Bit Ascii (RAW)' Slaves by four Modbus RTU Slaves. We are reading eight integer values from each slave.

In the older slaves, the data was almost available in one area of each slave. In the newer slaves the required data is at different places, hence the problem. Previously we were using only one BTW/BTR pair to read data (a max of 64 words can be read by this sequence) from all the four slaves and this arrangement was working fine.

But now it is forcing me (due to new RTU address mapping) to program two pairs of BTR/BTW sequences to read data from the same MCM 3100 module. Of course I will make sure that these two pairs of sequences do not conflicts when they get executed. But I am not sure what problems I may face and I request the forum to give your valuable suggestions and comments.
You are not reading very much data,
I imagine it's as though you were reading from 2 additional slaves.
Obviously it would be better if you could copy the data to a common area. I suggest you cal Prosoft's help line, I have always found them very helpful.

Thank you Roy for your prompt reply. I have the helpline numbers from their site and I will call them soon. Thank you.

RK Sastry