Yes, that is what I do. Wait for DONE or ERROR signal and then move on. I wonder if I should have more time after this so be 100% sure the previous block is inactive.
At least 151-8 CPU didn't like if time between Modbus serial querys was zero or too fast.
It halted CPU to stop on testing
p.s I had writing error on answer, it should have write if Done or error bit isn't setted.