Block transfer timeout with 1747-SN + 1794-ASB (flex IO) + 1794-OF4I (analog out)

I've got a SLC with a RIO scanner 1747-SN and a flex IO DIN rail 1794-ASB with an analog output module 1794-OF4I

Now I've found example code etc and read all the manuals fairly heavily however when doing the block transfer I keep getting error code -9 for the BTW and BTR indicating a block transfer timeout.

The 1794-ASB is flashing green which means it has the correct baud rate and is communicating, to confirm I change the dip switches to the wrong baud rate and the LED goes off.

If I had RS-485 comms to the remote IO scanner why am I getting a block transfer timeout? I've set the dip switches on the ASB to be logical rack 0, with the OF4I being the first module. This means it is logical rack 0, group 0, slot 0 (using full rack addressing).

I'm correctly setting the BTR word to be 000 for rack 0, group 0, slot 0. I've also tried setting the BTR word to be 100 and changing the dip switch to make it rack 1.

What else can I check? I'm pulling my hair out as I don't know what else can be wrong. Surely if I have the control word

The code I am using is example code recommended by rockwell support here, I've attached it as a zip also.

Any help would be muchly appreciated!

http://rockwellautomation-ap.custhelp.com/app/answers/detail/a_id/16036

You should have a solid green LED on the 1794-ASB adapter, not flashing green.

How many other modules are connected to the 1794-ASB ?

That example program you sent shows a "1/4 rack" at Rack 02, which would be correct with 1 or 2 modules connected.

Make sure you're configuring the DIP switches for the correct Series of 1794-ASB; the Series E modules (about 10 years ago) added 32-bit support and re-defined some of the DIP switch meanings.

I have a series D
http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1794-in098_-en-p.pdf

If I only have 1 module I should use 1/4 rack yes? If I used full rack with only 1 module installed what would happen?

Ok I see the problem, I had used full rack addressing as my full program has 4 modules, however I only have 1 module here for testing.

I've set it to be 1/4 rack addressing and it is now working. When I get the rest of the IO I will have to change it to full rack.

When a 1794-ASB powers up, it examines the I/O bus and the DIP switches and decides whether to represent a 1/4, 1/2, 3/4, or Full Rack of RIO memory.

You're on the right track. Configure it for what's there now, and reconfigure it later when you install the rest of the modules.

Thanks for the help guys, this is the second slc I've ever written code for and really got thrown in the deep end having to learn m, g files and block transfers with no greybeards to advise me.