SLC 500 Communications Question

[Andrew Evenson]

Hi all,

Just got a quick question about data transfer between 3 SLC processors. Ok, here is what I have; 2 SLC 500 (lets call them "A" and "B" that are read by another SLC500 "C" via ethernet.

Processor "C" interogates "A" and "B" for limit switch(s) status, sequence status and output status and uses this information to track products down a packaging line (Processor "C" is basically used to read product barcodes, weighing the produc and then tracking the product through the line - with information of product position status from the other 2 processors).

When production has to enter the line, they do a line lockout, and subsequently when power is locked out, processors "A" and "B" get powered down, not "C".

Now, in processor "C", this is causing me problems, as the states of the limit switches it is reading from the other 2 processors is changing because of the power down when the tracking code is not expecting it to chnage(Sometimes the plc's are powered down while processor "C" is in the middle of a sequence or has not finished a sequence, therefore causing duplication in product data entry into the line). Processor "C" is looking at wheather the other 2 processors are running, and I have tried to interlock this in the excecution of the subroutine that excecutes the tracking code (e.g Both processors "A" & "B" have to be runnig for x secods before code is excecuted) but that doesn't seem to always work. Does anyone have any idea's?? If i have not explained my question clearly enough then plase let me know.

Thank-you

Andrew Evenson

 

[Jimmie_Ohio]

Prior to shutting down the line, have some kind of "pause" pushbutton that signals processor C to stop looking for data. Then let the line be locked out...

 

[Oakley]

use a handshake status between the processors.

 

[curlyandshemp]

It's almost a situation where your processor 'C' needs a hardwired input as to the status of 'A' and 'B' panels. Is this prossible to do? Either run hardwire input from both panels A & B to C.

Ian

 

[Andrew Evenson]

Thanks

Gentlemen,

Thanks for all your replies, sorry it took so long to get back to you. I guess I'll have to take a better look at the problem, maybe some sort of handshaking or pause signal is necassary.

Thanks,

Andrew