MODBUS TCP/IP WRITE FUNCTION

[Kien_2512]

Hi everyone,

I'm currently working on establishing a connection between an M580 2040 redundant system and a DEIF AGC controller (Modbus server) using Modbus TCP/IP. I'm utilizing the DTM browser, and the Read/Write functions are performing well. However, an issue arises when I try to change parameters directly on the AGC controller screen (locally). The root cause is that the M580 continuously writes parameters to the AGC, preventing local changes.

I want to configure the system so that it only writes to the AGC when triggered by a specific action, such as pressing a button. I've attempted to use Read_Var and Write_Var, but they didn't work as expected. Can anyone assist me in achieving this functionality?

Many thanks.

[Bosswaffle]

What behavior are you experiencing with the read and write bar functions, and what is your goal? To read continuously and write based on a trigger?

[Kien_2512]

After reading the documentation, I was able to read and write to the device using the read_var and write_var blocks. Currently, I have 32 Modbus TCP/IP devices similar to the one mentioned. So I want to known how many devices can an M580 2040 PLC write to simultaneously using Modbus TCP? In the case of needing to use multiple write_var blocks, what should I do to prevent them from conflicting with each other?

[Bosswaffle]

In the help file it looks like the "maximum number of requests as client per scan" on a 2040 is 32. So, in theory you can write to 32 devices simultaneously, but probably not if you're also trying to read for them too. 

If I were you, I would make a few groups of these FB and add a counter and trigger the groups one at a time. Wait until the activity bits in the GEST array for each member of the group is zero and then trigger the next group.

[Kien_2512]

Thanks for your suggestion, It's Great!!!