What are the mode selection switches on the CPU panel in PLC? Here is an example of a panel that shows the full functionality of the CPU318-2:

Mode selector switch

As shown in the figure above, the following is an explanation of each one:

1. RUN-P position: it belongs to the running programming position, which can also read out and modify the program and change the running mode during operation;

2. RUN position: the CPU of the PLC executes and reads the program, but cannot be modified;

3. STOP position: does not execute user programs, but can read and modify programs;

4. MRES location: clear memory. When the mode selection switch is screwed from the STOP state to the MRES position, the memory can be reset to return the CPU to the initial state.

The specific operation steps of the reset memory: after powering on, screw from the stop position to the MRES position, the "stop" LED is turned off for Is, illuminates for Is, and then extends for Is to keep it on, at this time release the switch to let it return to the "stop" position, and then returns to "MRES" again, the "stop" LED flashes at a frequency of 2Hz for at least 3s, which means that the reset is being performed, and finally the "STOP" LED remains on the state.

The types of memory used by PLCs are: RAM (random memory), ROM, flash memory - Flash RPROM and EEPROM.

When we master the functions of the above mode selector switches of PLC, we can know how to use it correctly. I hope these introductions can solve certain problems for you!

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