Getting my butt whipped in Texas

I have a system that works perfectly. The PLC is a Modicon Momentum. It was programmed in Concept version 2.6 and IEC logic.

For reasons that are beyond belief and not worth going into the owner insists on having the logic converted to 984 LL. I can handle the logic, but I can't read the I/O. My supplier's guru is not available, and his backup is almost clueless. Using their suggestions I tried to write a simple program to test the I/O, with nothing more than one input turning on a single output. It is below. It doesn't work. What am I doing wrong.

The base is a combo analog and discrete. The I/O configuration is attached.

What am I doing wrong?

Here is the I/O configuration.

Well Tom, I don't know if this is any help or not.

I haven't messed with Modicon in years, and then not all that much to start with.

As I recall, the 984 had the bit numbers and some others in reverse order, and it drove a lot of people batty trying to get it straight. I'm not sure, but it may have carried over to register ID numbers, etc.

As I said, it's been a long, long time.........

regards...casey

As I recall, the 984 had the bit numbers and some others in reverse order, and it drove a lot of people batty trying to get it straight.

Click to expand...

Casey is right the darn bit numbers are bassackwards if my memory serves me correctly. 0 = 15 and 15 = 0. At least for that pesky Momentum, little plastic box! Try that Tom, I used to work for Modicon, you'd think I could remember for sure.

bitmore
ps. is it little injun, big injun for the word assignment?

Tom,

The module terminal wiring is based on the IEC world of 0-15 right to left, however the interpretation of the bit pattern is processor dependent.

984 Ladder Logic bits   1  2  3  4  5  6  7 8 9 10 11 12 13 14 15 16

Momentum Processor bits 15 14 13 12 11 10 9 8 7 6  5  4  3  2  1  0

Momentum base terminals                       9 8  7  6  4  3  2  1 

[\ladder]



An easy way do see this is to use a BLKM command to move your 3x1 register to 16 consecutive 0x coils.

got to learn to preview before sending

984 Ladder Logic bits   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Momentum Processor bits 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Momentum base terminals                       9 8 7 6 4 3 2 1 

Thanks guys. It turned out there were three problems. The first is that, as you indicated, input one is in bit 16. Second, the comm adapter expansion base default data range was 400007 to 4000027 which overlaps the default Ouput range of 400001 to 400012. Finally, word one of the output range must be set to nonzero to enable the outputs.

Here is the logic that worked, with input 7 turning on output 3.