AB remote I/O

BTR is Block Transfer Read and BTW is Block Transfer Write. The information that will tell you what the bits in the five integers mean will be in the manual that deals with the particular card. So, look in the 1794 manual and look up the command words and status words for it. These are the ones you use BTR and BTW to transfer from or to the card.

The 1794 manual is on-line at Rockwell's site.

Thanks Paul, I had downloaded and read all manuals concerning the 1794 mods and they talk about the Data File but nothing about the Control Block. I have gathered from the Instruction Help for BTR,BTW that the bits 07-15 are status and 00-06 store the modules address but this is only word #1. What are the other 4 words of data for? Is this something I need to program or is it more instruction status bits? Just not sure what I need to put in these other 4 data files. Am I just not looking at this correct?

Each word of the part of the control block you're referring to is module specific. If you're using RSLogix 5 the module setup dialogue box will set those words for you. Use the IO configuration that the RSLogix provides for you. It's in the project tree. Install the chassis in the program, and choose the ASB module you're using to communicate with the flex IO rack. You'll need to provide a starting Rack and Group number as well as the number of slots in the chassis. Once that's done you can pick which module you're using and which slot it is in simply by doublr clicking a vacant slot in the chassis. At that point you configure the model and the appropriate values are written to the words in the control block you're concerned about. It's done for you.

I assumed (I know, I know) that you're using RSLogix5. If you're still using ICOM or 6200 software gooooood luuuuuck :)

To add to that answer I would need to look at the books at work. It will be after the weekend as tomorrow is a busy day in operations.

One other thing I forget to mention. Don't try to manually create the BTW/BTR rungs yourself. Once you've configured the module inside the module configuration dialog box click the button "Insert Ladder Rungs". Let the software Autopick and create the data files needed for the block transfer instructions. Then you'll choose which ladder file to create the rungs in. If you have an existing block transfer ladder file tell the software to put it at the end of the file. If not tell the software to create a new file. It's a fairly intuitive process and pretty easy to accomplish.

I remember the first time I had to add a 1771-IFE module (Analog Input) to a spare slot in an existing rack using the older software that AB provided. Took me quite a while to complete what I thought would be a fairly simple task. It's much easier these days. Let us know how you make out...

Exactly which PLC-5 processor and what programming software are you using? Any fairly modern PLC-5 (past 15 years or so) will also use the BT data type for the control block, which makes your issue moot, as the sub-elements will be named rather than numbered. I will nonetheless do a bit of research on your behalf.

Enhanced PLC5/20 16,384K Mem. Also one thing I didn't mention is that this is an existing system and I need to add to it. There is existing ladder logic using BTR/BTW instructions.

Thanks for the info.

RSLogix 5 software

It doesn't matter whether he's using a "Classic" processor (5/25 or below) or enhanced processor. With RSLogix5 you do not have to manually configure the data file for the BTW/BTR. You do not have to manually configure the control block words either. That's data that RSLogix automatically configures and is used by the processor to complete the transfers. There is no reason to fart around with them. During the module addition in the IO config all data written to the appropriate data block is done for you. If it's attached to an older processor the appropriate integer words are automatically written. If it's one of the newer processors the BT (block transfer data types) are automatically written. Both cases are contingent on letting the software insert the ladder rungs containing the block transfers, however. In older versions of the software I/O was a pain in the ass. Not really the case anymore. Hours spent perusing a module specific manual looking to set individual bits or entire words in a BTW data block are long gone. You could spend the hours needed to do it the manual way like the old days, but I don't want to lose any more hair. I can't afford it any more...

RSLogix5 is natively aware of all 1794 I/O. You pick the module you want to install from a list inside the software. Every module is listed once you specify Flex IO in the "Add Chassis" dialog box. Once the module is installed the software knows how to handle the BTW/BTR pair for the specific module.

You may find the answer you need in AB manual 1785-6.1, page 15-5, available at

word 0 - status bits word 1 - requested word count word 3 - transmitted word count word 4 - File type-number word 5 - element number

I provide this information as a direct answer to your direct question.

Bear in mind however, that, as others have pointed out, the need to know this information proves that you are on the wrong track, unless you are trying to reverse engineer an old program. The best way to add new block transfers is to use the configurator accessible from within the "I/O Configuration" folder in the project window of RSLogix 5, and to use an element of the BT data type as the control block. There is really no reason at all to be concerned with how the control block is organized.

Thanks to everyone for the info, it is apprecitated