Alan leach

Fx series plc fixed buffer comms between 3 plc's

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Hi everyone I have a project where i am using fixed buffer comms to communicate between x2 fx3u plcs. The code is working well and no issues. The have ethernet modules set up with fx configurator software I now need a third plc to communicate to one of the plcs So plc 1 and 2 send and recieve to each other, now plc 3 needs to communicate to plc 1 Im using non procedure exists method, the networks fine can ping etc, Fixed buffers 1 and 2 are used already but cant get any of the other fixed buffers to work Has anyone very done this, any help would be very much appreciated. Thanks Alan

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That should be no problem. What software are you using? Are you using any kind of FunctionBlocks? Are any of the other ports/buffers (3-8) in use for anything else?The way to do it is simply to "copy" the existing working code inside PLC1 and paste it again. Then just modify the buffers to use fixed buffer 3-4 instead of 1-2. In PLC3 you just copy the code from PLC2. Just remember to adjust the IP addresses, and use different port numbers on PLC2 and PLC3 (never use the same port numbers twice in the same PLC).

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Thank you for reply I have tried that several different ways Software is gx developer Ports 1&2 are used between 1and 2 buffers 1&2 Ports 3&4 are used between 1&3 respectively What ever way i try and do it i cant get any of the other fixed buffers to Send or recieve, Point to note if 1&3 are changed to buffers 1&2 it works I have read through the fx3u manual and my send and recieve code is nearly identical to there example

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What is your setup in FX ConfiguratorEN? Could you make a screenshot? And as a note: Both PLC's need two buffers each. So PLC2 = Buffer1+2, PLC3 = Buffer3+4 (in PLC1)

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Key point just noticed ! Do i have to change the port number in plc 1 for the send and recieve to plc 3 So 1-2 is port 1040 in 1 1030 in 2 So if i set channel 3 and 4 in plc 1 to 1050 Plc is port number 1025 Cheers Alan

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Should of been plc 3 is port 1025

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Yes: Never use the same port number inside one unit more than once. This is because the port number is a number between 1-65534 (65535 = "Accept all"). So basically if you assign a port, you cannot use the same port in a different buffer. All the buffers share all the ports inside one unit.

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Makes sense !! Thanks ver much ! One other question i cant fathem out... If i send in plc 1 to buffer 1 1665 with a length in 1664 of k10 How does it get recieved in plc 2 in 2688 buffer 2 ? So if i use buffers 3 and 4 i send to 3713 buffer 3 in plc 1 and recieve as 4737 buffer 4 in plc 3 How does that work ? Thanks for your help i doent all day on this today

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No problem. It works because you use buffer 1 (and 3) for sending, and buffer 2 (and 4) for receiving. So if you imagine the following from FX ConfiguratorEN using PLC1 as an example: PLC1 - PLC2 1 -> 2 2 <- 1 PLC1 - PLC3 3 -> 4 4 <- 3

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Of course Many thanks for your time !!

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