Mitsubishi Programmable Logic Controller）

Set and reset instructions (SET/RST)   (1) SET (set instruction) Its function is to set and maintain the target element being operated.   (2) RST (reset instruction) resets the target element being operated and keeps it in the cleared state. When the SET and RST instructions are used, when X0 is normally open and connected, Y0 becomes ON and remains in this state. Even if X0 is disconnected, Y0's ON state remains unchanged. Only when X1 is normally open and closed, Y0 becomes OFF and remains in this state. Even if X1 is normally open and disconnected, Y0 remains OFF.   Instructions for using SET and RST instructions:   1) The target elements of the SET instruction are Y, M, S, and the target elements of the RST instruction are Y, M, S, T, C, D, V, and Z. The RST instruction is often used to clear the contents of D, Z, and V, and is also used to reset the cumulative timer and counter.   2) For the same target element, SET and RST can be used multiple times in any order, but the last one executed is valid.   Master control instructions (MC/MCR)   1) MC (Master Control Instruction) is used for the connection of common series contacts. After executing MC, the left busbar moves behind the MC contact.   2) MCR (Master Control Reset Instruction) It is the reset instruction of the MC instruction, that is, the MCR instruction is used to restore the original position of the left bus.   In programming, it often happens that multiple coils are controlled by one or a group of contacts at the same time. If the same contacts are connected in series in the control circuit of each coil, a large number of storage units will be occupied. Using the main control command can solve this problem.   MC and MCR instructions use MC N0 M100 to move the left bus right, so that Y0 and Y1 are under the control of X0, where N0 represents the nesting level. In a non-nested structure, N0 can be used an unlimited number of times; MCR N0 is used to restore to the original left bus state. If X0 is disconnected, the instructions between MC and MCR will be skipped and executed downward.   Instructions for using MC and MCR instructions:   1) The target elements of MC and MCR instructions are Y and M, but special auxiliary relays cannot be used. MC occupies 3 program steps and MCR occupies 2 program steps;   2) The main control contact is perpendicular to the general contact in the ladder diagram. The main control contact is a normally open contact connected to the left busbar and is the main switch that controls a group of circuits. The contacts connected to the main control contact must use the LD or LDI instruction.   3) When the input contact of the MC instruction is disconnected, the cumulative timers, counters, and components driven by the reset/set instructions in MC and MCR maintain their previous states. Non-cumulative timers and counters, components driven by the OUT instruction will be reset. When X0 is disconnected in 22, Y0 and Y1 will become OFF.   4) Using MC instructions again in an MC instruction area is called nesting. The maximum number of nesting levels is 8, and the numbers increase in the order of N0→N1→N2→N3→N4→N5→N6→N7. The return of each level uses the corresponding MCR instruction, and resets from the nesting level with the largest number.   Differential instructions (PLS/PLF)   (1) PLS (rising edge differential instruction) generates a pulse output of one scan cycle on the rising edge of the input signal;   (2) PLF (falling edge differential instruction) generates a pulse output of one scan cycle at the falling edge of the input signal.   The edge of the signal is detected by the differential instruction, and the state of Y0 is controlled by the set and reset commands.   Instructions for using PLS and PLF instructions:   1) The target elements of PLS and PLF instructions are Y and M;   2) When using PLS, the target element is ON only within one scan cycle after the drive input is ON, and M0 is ON only within one scan cycle when the normally open contact of X0 changes from off to on; when using the PLF instruction, only the falling edge of the input signal is used for driving, and the rest is the same as PLS.