Instruction Parameters
Supported PLC Series
| PLC-AES | PLC-FB | PLC-ES |
|---|---|---|
| ✓ | ✓ | ✓ |
Supported Data Registers
| M | X | Y | K | L | F | T | C | S | Z | R | Q | D | @D | Constant | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n | – | – | – | – | – | – | – | – | – | – | – | – | – | – | ✓ |
Supported Flags
| Flag | Bit | Support |
|---|---|---|
| Error | F11.0 | ✓ |
| Zero | F11.1 | – |
| Carry | F11.2 | – |
Number of Steps
| Steps |
|---|
| 1 |
Operands
| Operand | Description |
|---|---|
| n | The only operand. Entries are only constants. This is the identifier for the start of the master control area. If nesting master control, the value range is 0 ~ 7. |
Notice
Notice
A compile error will occur when the number of nests, n, is greater than 8.
Execution Behavior
When a ladder with master control contains instructions that do NOT require contact instructions, such as the FOR and NEXT instructions, the CPU module executes these instructions regardless of the ON or OFF status of the MC instruction execution command.
Instruction Behavior
The MC instruction behaves as follows:
- MC n indicates the start of the master control area.
- This allows for circuit switching efficiency.
- When the execution condition of the MC instruction is ON (1), master control starts operation.
- When master control starts, the program is executed from MC n to MCR n where n is the same number.
- When the execution condition of the MC instruction is OFF (0), master control does NOT start operation and the MCR instruction is not executed.
- The MC and MCR instructions can be nested.
- MC ~ MCR can be nested up to 8 levels (0 ~ 7).
- If MC ~ MCR instructions are nested in other MC ~ MCR, the nesting number, n, is available from lower to higher with the MC instruction and higher to lower with the MCR instruction.
- Please refer to Master Control Example 1.
- When nesting is composed in reverse, a compile error occurs.
Master Control Area
- Master Control is defined as a control area within the ladder logic for executing certain parts of the ladder logic code.
- Master Control will execute from MC n through MCR n where n is a constant.
- If MC ~ MCR instructions are nested in other MC ~ MCR, the nesting number, n, is available from lower to higher with the MC instruction and higher to lower with the MCR instruction.
- MCR with the lowest nesting number can terminate all master controls when:
- MCR instructions are nested in one place.
- There may be MC instructions with higher nesting numbers, n, within the MC ~ MCR area with the lowest nesting number, n.
Ladder Diagram Examples
MC
The MC instruction declares the start of a Master Control area.
Example 1
The Master Control area will execute the INC instruction every second if the contact, M0.0, is ON (1).
When the contact, M0.0, is powered ON (1), the INC instruction executes every second. Every execution condition within MC 0 ~ MCR 0 will execute until M0.0 is OFF (0).
When the contact, M0.1, is OFF, MC 1 will NOT execute. Even though the contact, M1.0 is powered ON (1), the DADD instruction will NOT execute.
When the contact, M0.1, is powered ON (1), the DADD instruction will execute. Every execution condition within MC 1 ~ MCR 1 will execute until M0.1 is OFF (0).
Example 2
This example shows the lower to higher nesting order for the MC instruction where the MCR instruction terminates with the lowest possible value, 0.