Multiple FIFO's into 1 FIFO

James Mcquade said:

First off, what plc?
may I suggest the following.
1. write down in your own words how each fifo load / unload works.
2. when this is done, think about what needs to happen next and write that down in your own words. think of the existing fifo logic as staging areas for a central system.
3. then write down what the staging areas need to for for the last fifo (exit conveyor).

james

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JosephMont said:

Its an L84ES. I have all the other FIFO's working great and deployed in multiple different PLC's working amazing. Its when they get loaded into the last FIFO I am having a 3-5% failure on the load when using more than 2 FIFO'S going into one FIFO since they are all using the same entrance.

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James Mcquade said:

If I understand you correctly,

3 fifo's working great on 3 different plc's
you have a conveyor system (for example) which is fed by these 3 plc systems.
they all merge onto the last conveyor at the same point.

if this is the case, may I suggest the following.
1. allow 2 of these conveyors to merge together and create a fifo for them.
then merge this line with the last conveyor and create a final fifo.

OR

2. create staging logic for the 3 systems to merge into the last system.
this will involve a fifo for the staging of the containers.

since I don't know your exact layout, I can't give much help beyond this.
I used to work for a conveyor oem and we had to stage things, they just couldn't all hit the last conveyor at the same time for the reason you are experiencing, 2 or more boxes entering at the same time. the fifo got confused.

james

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thingstodo said:

If you somehow get to executing more than 1 FIFO LOAD (FFL) per plc scan, you need to unlatch the fifo.EN signal before executing the FFL for each load.

Attached is working code that we use to send commands from our DeltaV to our L73s via Mynah's VIM interface

The commands show up in the N_FILE_1 array, we keep track of the last command loaded for each location and each DeltaV, and the command goes to 0 before the next command is sent

The commands are loading into 1 FIFO, the processed one per scan.

We have multiple FIFOs into one FIFO for reporting back to our PI system ... but I am not confident that we are not experiencing losses there. I hope that you are seeing losses due to this issue, as I don't have multi FIFO code to share. We DID experience losses on commands from multiple DeltaV's .. once in a while .. before this fix.

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