Mitsubishi plc M: Auxiliary relay (equivalent to the intermediate relay in the electrical diagram). His control method is the same as Y, but there is no output port, just a single device. Like Y, there are coils and normally open, normally closed contacts.
When multiple control methods use the same type of Y. At this time, direct control may cross, and the program may appear complicated. At this time, you can use M to control.
For example: you have to control 5 different modes of Y0. If you control Y0 directly, it will generate a lot of interlocks (you should prevent the other 4 modes from working when you use one mode) to make the program complicated and error-prone. (At this time, you will feel that if there are 5 Y0, then how good it will be, but if you use it again, there will be double coils.) If you use 1 M coil instead of Y0 coil for each control mode. Then use the contacts of the respective M to control Y0. When M gets electricity. Y0 will also be powered. (Is it equivalent to 5 Y0)
M: FX2N series range (default) M0-M499 is a normal auxiliary relay M500–M1023 is a latch auxiliary relay (power-off retention type)