DO-DCM and directsoft5.1

[Kyle L]

Newbie here,
Why is the AIN instruction limited to 128 bytes of input?
I have another device that sends out 244 bytes of data in one write to the comm port.
Is there a way I can read all of the data by using multiple AIN intructions nested together?

[franji1]

That is a PLC limitation.  The most amount of data it can transfer in a single request across the backplane is 128 bytes.

I don't think you will be able to chain multiple AINs together because by the time your ladder logic recognizes it has received 128 bytes and then you start another AIN, you will have missed a few characters.   

Someone on Automation Direct's forum may know more about the capabilities of the AIN instruction and give you a better answer.  http://forum1.automationdirect.com

[Kyle L]

Do you think it would be better to use the FO-CP128 Basic Coprocessor Module rather than the DO-DCM module?

[franji1]

Yes!  That should definitely do the trick, but you gotta program it.  It's made by FACTS Engineering - you can probably check Automation Direct's forum for help with that!

[Kyle L]

 8)Thanks for your help.It is always appreciated