Buffer does not update? AB 1400

[deathbysnusnu]

Hi, guys!

I have been stuck for a while on the same issue and would be very grateful for some input. The first time I toggle start ON the string in the buffer is sent to ST9:4. But if I toggle start ON again, it never updates ST4:4 with (what I believe should be) the most recent entry from the buffer. It is like the buffer is no longer being updated with the string sent from the serial terminal. And I don't understand why it would fail to repeat the same process by just toggling start ON again. Can someone see why?

Many thank yous

Picture and program, Micrologix 1400 A

 

[deathbysnusnu]

Hi, again! Just would like to say (in case someone else find themselves with the same problem in the future) that by looking at my program with more scrutiny I noticed that the done bit of ABL and ARL were always ON after the first run. So the way I went around that was to reset the control files for ABL and ARL in parallel with ACL (rung 1).

 

[Epy]

Without testing that on a ML directly, you need to check:
- are all bits getting reset, e.g. does R6:0/DN reset at some point when you toggle start? Does R6:1/FD? Does the timer done bit? I don't use the ASCII instructions often (end up using MSG instead), but that'd be my guess is one of the bits of R6:0 or R6:1 isn't getting reset (and therefore it isn't toggling those instructions, need the off to on transition to activate the instruction)
- is the device you're talking to programmed to respond once or each time it's talked to? is it responding correctly? is it working correctly?

Edit: just saw you figured it out, nevermind.

 

[deathbysnusnu]

I also had to reset R6:2/DN (ARL) or else it would not update ST9:4. For some reason though I don't seem to need to reset R6:0/DN, but I can only assume that is coming when I add more AWA instructions to the program. Thank you for the input, Epy, it was spot on.