Hello,

it is expected to take to account more things, like comm blocks end signal values due scan of CPU and of course your correct handling of state signal to change between modes for different task. I don't know if this is your problem also, RTU protocol is half duplex basically so you need also simply end one task, check signals, change to other task and start it, there isn't possibility to start more tasks at one time. To this description you need prepare your code. One important thing is, in case of problems with tasks, comm block settings can set some rules as timeout between messaging, error state and reset of communication, sometimes repeat of send some message till error is clear to know after defined value of this cycle. All is described in Help to specific block, in your case MASTER block.