I have a Modicon Quantum PLC that is using MSTR instructions. There are presently three connections on the instruction. The top input node which initializes the instruction, and the center and bottom output nodes. The bottom output node goes true when the MSTR is completed. The manual I have indicates that the center input node on the instruction stops the MSTR instruction and that the center output mode echos that state. That is, if there is an input on the center node, there is an output on the center node. However, the program I am working with (developed by others) has no input connected to the center node and is using the center output as a "MSTR Failed" bit; and it seems to be working. My question is: does the instruction itself generate a signal on this output if the instruction fails, and if so, after how much time?
