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MES-Terminal interlocks
Three Boolean variables are required.
| Variable | Type | Description | Direction | |
|---|---|---|---|---|
| HeartbeatToMES | BOOL | Blinker signal from PLC in three-second cycle (maximum 3 sec. signal pause and maximum 3 sec. signal) | From PLC to MES | |
| HeartbeatToPLC | BOOL | Blinker signal from MES to PLC | From MES to PLC | |
| EnableMachine | BOOL | MES set this variable. The machine may only start automatic mode if this variable is set to TRUE. Attention: If the status of HeartbeatAnSPS does not change for e.g. ten seconds, EnableMachine has to be ignored. | From MES to PLC |
Signal status diagram 'MES terminal interlocks'
The pulse can be generated either by the PLC internally or in TC2/3 by the block MES_Lifebit.
- Section 1: Machine gets release from MES-Terminal.
- Section 2: MES-Terminal withdraws machine's enable (the next cycle should not be able to start). Recommendation: If EnableMachine = FALSE and the next cycle should be started, there should be a PLC error message, e.g. “Machine has no release from MES-Terminal”.
- Section 3: Use case “Production without MES system”: If HeartbeatToPLC is not written, the machine is released as failover.
| HeartbeatToMES | HeartbeatToPLC | EnableMachine | Is machine enabled? | |
|---|---|---|---|---|
| Toggle | Toggle | TRUE | TRUE (see section 1) | |
| Toggle | Toggle | FALSE | FALSE (see section 2) | |
| Toggle | FALSE | TRUE | FALSE (not possible) | |
| Toggle | FALSE | FALSE | TRUE (see section 3) |
