Queuing in ladder logic using only the 4 basic operators

[danatomega]

You would also need the development software and maybe the simulator and almost certainly the compiler for the PLC.

Another alternative would be to get an Automation Direct PLC and use it to do the 'queuing' using digital I/O if needed to inform the MicrLok PLC of the box's status when it gets to the diverting portion of the system.

 

[jendrus]

to add a new bit to the "buffer":

 C    Add   D  
-||---||----()
          |
 D    Add |
-||---|/|-|

C->D
B->C
A->B
New->A

to remove one from the buffer, you would need to track how long the buffer is, and pull that data out. You might need, essentially, a parallel buffer that only has one bit true, to track which element of the FIFO buffer is the one to read out of. You'd need to write the read command for all the possible elements, and only one would execute, then you'd have bump the parallel buffer down one.

In practice, this would grow super tedious very quickly if you need a FIFO buffer bigger than 3 or 4 layers deep.

Thanks for the ideas. I am only using a buffer that's 3 or 4 layers. What I'm a little confused on us do I need two buffers for the two boxes of just one?
Also, I guess I can use a micrologix unit and do the fifo there, will require some wiring and hardware changes so I would like to avoid but if necessary I will look into

 

[rdrast]

If you really can't upgrade it (and serial comms are trivial to implement nowadays to be honest), can you possibly just add a new PLC to handle your advanced logic and send outputs to the old, slow, non-configurable thing you have?