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Hi, I'm writing an application involving 1 master and 9 slave controllers - all Unitronics. The master PLC is a V1210. One of the slaves is also a V1210. The remaining 8 slaves are V130s. All i'm trying to do is sequentially read 1 coil from each of the slave PLCs. I know that this should be ridiculously easy... ...However, I'm finding that the "Function in Progress" bit gets stuck on after the master only attempting to read from 2 of the slaves. I've tried using timers of 100ms - probably excessive - after each Modbus Read Coils function block. Also, just to mention, I don't have all 9 slave controllers with me for testing - I've got 2. Is Modbus good at handling when it can't get thru to a particular node and just moving on to attempt the next one? Any help much appreciated, James
I have an application where I need to have one V130 PLC communicate to three V120 PLCs and read a bunch of MI registers. I have the V120 systems already supporting Modbus comms over RS485. So, I setup the V130 to be a Modbus Master and talk to all three Modbus slaves. I setup the Com port for RS485 with the appropriate properties. Then I have a RHR command to read from the first PLC. And this works just fine. I can read the Modbus registers from PLC1. Then I have two more nets with an RHR command to read from PLC 2 and PLC 3, but these nets don't seem to execute at all. What am I doing wrong? Is it even possible to have one Master talk to several slaves with the Vision PLCs? I saw a reference to some timing issues and that you maybe should add some delay time between RHR commands. Is that what needs to happen. I need some help ASAP. I need to deliver this system in a couple of days. Thx,