Allen Bradley Block Transfer


Thread Starter


Hi guys!

Good day!

I am currently working with a Allen Bradley Panelview RIO application migration to PanelView Plus 1250. I am stuck with the interpretation of block transfers. Can someone help me interpret them? This is my first time working with Allen Bradley, especially RIO and Block Transfers.

1. Tag_BO2_7_0-7_15_Bin_22

I understand that BO2 means a block transfer write file 2. The next digits are the ones that I can't interpret. also,in the block transfer block with the following code :

Block transfer Write
Module Type: Generic Block Transfer
Rack: 006
Group : 0
Module: 1
Control Block: N13:60
Data File: N9:32
Length: 32
Continuous: No

I would like to follow where the given tag has gone after it entered the block transfer. My idea is data file N9:32, but where in that data file?

Any tips and ideas are very much appreciated.

Thank you.

Trevor Ousey


You don't specify it but it appears that this may be in a ControlLogix?
Maybe not.

The tagname displayed looks like a format that the person who wrote the program created, and probably does have some structured meaning but not the requirements for the program.

It does appear that data file is N9:32 with a length of 32 words (ints) meaning that it is N9:32 to N9:63 for the Block Transfer. Block Transfer Writes send data to the PV and Block Transfer Reads read data from the PV. Also with PV's on RIO there is direct IO control, for example O:60/0 could be an inductor on the PV and a button could be I:60/1.



Hi Trevor,

I forgot to mention that this is a PLC 5.

Thanks for the reply, I was able to follow the bits and data and I'm simulating them right now.

I would like to have a follow question, Why is it my Numeric or Analog data are updating very slow? While binary signals are working fine? It takes 20 seconds or more before the analog data is written in the PLC...?

Thank you.

Trevor Ousey


Get hold of the manual from he AB website, it is free, and will help understand the Block Transfer function. Then check your PLC program where the BTR and BTW instructions are to be sure they are setup correctly. I assume the binary bits are directly mapped with the IO structure and the BT instructions are used for analog words, so this would either point to the instructions or BT section of the PV. RIO should be quite quick.

If you want, you can contact me off-list at tousey{at}oozemail{dot}id{dot}au

Hi AbdouGTL,

I guess what you actually mean is "Generic Message instruction" at Controllogix/RSlogix 5000 rather than "generic block transfer".

In Controllogix there is "Mesage " instruction that support several modes, not only "CIP messaging" for Logix platform but also support legacy messaging from PLC-2/5 or SLC platform such as "DH+ messaging" or "Block Transfer Read / Write" for PLC/ SLC IO module or for Panelview.