Programming Mitsubishi A Series

[BobCully]

On a standard(ish) processing machine that we produce, I have several (maybe 20) sequence programs running simultaneously. To step through each sequence I arrange a group of flags into a shift register- 8,12 or 16 bits long.
The first flag in the group (the lowest) is forced on when the sequence begins, and that flag controls that `Step' in the sequence. When that step finishes I give a SFL K1 instruction (shift left 1 position), which turns that step flag off and the next one on. It works fine.
Sometimes however things don't go as planned, and a switch (or something else) doesn't make and the sequence stalls. What I need is and indicator to tell me which step of the sequences is on at any time, and what I'm looking for is an elegant way to return a number corresponding to the position in the sequence of the `on' flag - just as a (step) number. For example, `M251 K2' defines a set of (K)2x4 flags starting at M251, M251 being the first bit and M258 being the 8th. I want a function that will hold in say register D250 the value 1 to 8 depending on which flag is set. I eventually want to have a page on the MMI to report the status of all these Sequences. I haven't been able to figure a way out of how to do it `in the back-ground' while the sequence is running. All I've been able to come up with is to include a line in each step of the sequence to say `INC D250', and then zero it at the end of the sequence, but its a bit messy.
Has anybody any thoughts?, do other PLC's have a neat command for doing this (and how does it work)? (but I'm not going to change!).
Regards

 

[SteveMeisel]

Not being familliar with Mitsubishi PLC's here is one way of doing it is:
Bit 1 is true it moves a 1 into the register
Bit 2 is true it moves a 2 into the same register
Etc. Etc.
Then if all bits are false move a 0 into it.
Then all you have to do is just display the value of that register. I am sure that someone with more knowledge on your plc will be of more help. Good luck.

 

[BobCully]

Thanks for your reply Steve, and I'm sorry to have taken so long to respond. I've only just read it, and at first I thought it would be a very long winded way to do the job (but of course it will work). However, after a few minutes to allow the idea to sink in, I am sure I should be able to rig up a loop just to step through the no. of steps in that sequence.
Thanks again,
Bob