Chapter 5 Basic Instructions Symbol MC N ： Level of the nested program structure N0~N31 MCR Explanation 1. MC sets the master control. When the MC instruction is executed, the instructions between MC and MCR are executed as usual. When the MC instruction is OFF, the actions of the instructions between MC and MCR are as described in the following table. 5_ 2. MCR resets the master control, and is placed at the end of the master control program. There should not be any contact instruction before MCR. 3. MC/MCR supports the nested program structure. There are at most 32 levels of nested program structures (N0–N31). Refer to the example below.
5-7 Instruction code Operand Function MC/MCR N Setting/Resetting the master control Instruction type Description General-purpose timer The timer value is reset to zero. The coil and the contact are OFF. Timer in the function block The timer value is reset to zero. The coil and the contact are OFF. Accumulative timer The coil is OFF. The timer value and the state of the contact remain the same. Counter The coil is OFF. The timer value and the state of the contact remain the same. Coils driven by OUT All coils are OFF. Devices driven by SET and RST The states of the devices remain the same. Applied instruction All applied instructions are not executed.
The FOR/NEXT loop is still repeated N times, but the actions of the instructions inside the FOR/NEXT loop follow those of the instructions between MC and MR.