AB "SQO" Sequencer Output Help

[bowler 0]

I just joined the Fourm. After browsing thru the posts there looks to be many wonderful and intelligent people here. Okay here is the problem, I am just starting out learning AB programming and I am working with a "SQO" File #B9:0 Mask 94BF Dest. O:2.0 Control R6:2 Length 13< Position 0< It seems to work properly except that when you stop it in the middle of the file. The rung goes false and the position resets back to zero, but the outputs stay energized. What am I doing wrong? This is in our "Plug and Play" board set-up, we have a 5/03 processor with 1 input and 1 output card.

[TConnolly 13]

When you reset the sequencer you are only resetting the value of the R6:0.POS word, but it doesn't automatically mean that the ouputs get updataed. The sequencer instruction itself must be executed to cause a change in the outputs and the SQO only operates on transition of the rung from false to true. So some other instruction must be used to reset the output. Thus when you reset the sequencer also program a branch on the same rung with the reset to MOV the default value to the output word. edit: If this isn't the answer you are looking for, then repost and attach a copy of your program and I'm sure we can help. If you will scroll down in the reply window you can see how to attach a file. Edited 15 Feb 2008 by Alaric

[OkiePC 14]

If you put the SQO on an unconditional rung and externally manipulate the control.POS, the outputs will be constantly update, but to turn them off you will have to "bail out" of the sequence by writing 0 to the control.pos. The more practical and flexible alternative is to change the destination to a bit file word address, (ie. B10:000). And then use those bits to enable each output with simply XIC --> OTE statements. All the while, the conditioned SQO won't update and instead remembers the states and step number. Then you can go back through simple "output map" and put a mode contact is series with the outputs to turn them off when the mode stops, Always put this output map at the end of your code. If you map the inputs, do that first in your ladder logic. Put your mode control logic ahead of the sequencer instruction. What if you want to resume? Now, your ladder logic can decide whether or not to reset the position, or resume. You can make that decision part of the SQO data, since now you are not limited to real discrete outputs. You can use the SQO to select and deselect different operations that YOU define. For example: One of your SQO output bits could become "allow resume" and you can configure the machine behavior , just by "pegging" in the right commands as "1"s and "0"s in the sequence chart.. The other advantage is that you can "re-wire"...What if you have 37 steps and you want to move a motor starter from O:1/7 to O:1/13? It is easy if you remap the real inputs and outputs as described above. Otherwise, you have to change 37 bits in 37 different words. Hope this helps without adding too much to the assignment. Opinion: Instructors whould teach more structure with sequencers. They teach the concept of data and I/O mapping, the day before they begin drum sequencers training. Edited 16 Feb 2008 by OkiePC

[paulengr 44]

It might be a little confusing because you aren't pairing it with the SQI instruction. The SQI instruction acts as a filter to trigger the SQO instruction to advance whenever all the appropriate input conditions are set. Frankly, these instructions are both limiting and somewhat difficult to debug. You would be better off designing a state machine the traditional way (with a bubble diagram) and implementing it that way as well. It is easier to troubleshoot and not limited to the strict "A,B,C" ordering of the SQI/SQO instructions.

[bowler 0]

Thanks again to all that replied. Alaric's answer was what I was looking for.