PMTR Command Source
The Process Motor (PMTR) instruction uses these command sources. The command sources are prioritized in order from highest to lowest in this table.
Command Source | Description |
|---|---|
Hand | Hardwired logic or other logic outside the instruction controls the device. The instruction tracks the state of the device for bumpless transfer back to one of the other command sources. This is the highest priority command source. |
Out-of-Service | The instruction is disabled and accepts no device commands. |
Maintenance | Maintenance controls the device and supersedes Operator, Program, External and Override control. Operator commands and settings from the HMI are accepted. |
Override | Priority logic controls the device and supersedes Operator, Program and External control. Override Input (Inp_Ovrd) is accepted. |
External | External logic (for exapmle, field pilot control or upstream SCADA) controls the device. External commands (XCmd_) are accepted. |
Program locked | Program logic controls the device. Program commands (PCmd_) are accepted. Operator cannot take control from the Program. Override cannot take control from theProgram unless Cfg_OvrdOverLock = 1. |
Program | Program logic controls the device. Program commands (PCmd_) are accepted. |
Operator locked | The Operator controls the device. Operator commands (OCmd_) from the HMI are accepted. Program cannot take control from Operator. Override cannot take control from Operator unless Cfg_OvrdOverLock = 1. |
Operator | The Operator controls the device. Operator commands (OCmd_) from the HMI are accepted. This is the lowest priority command source. |
The instruction enables or disables these operations:
- Maintenance Out-of-Service exists
- Maintenance exists
- External exists
- Program (unlocked) exists
- Program locked exists
- Operator (unlocked) exists
- Operator locked exists
- PCmd_Lock used as a Level (1 = Lock, 0 = Unlock)
- XCmd_Acq used as a Level (1 = Acquire, 0 = release)
The instruction checks for invalid configurations of control and forces the nearest valid configuration.
The core control model arbitrates the source of the commands and parameters that the receiving function accepts. The core control model determines if the source is:
- A programmatic entity which resides entirely within the processing environment, or
- An external interface entity which issues commands and parameters external and asynchronously to the processing environment.
Locking a control source prevents the other control source from acquiring privilege.
Core Command Source Model
The core control model consists of these control sources:
- Oper
- OperLocked
- Prog
- ProgLocked
The control model defaults to this configuration. Other control sources may be present in the model but act as overriding control sources, acting independent of the base Operator/Program state machine.
Enable control sources as Configuration
The user can enable and disable individual control sources. The default configuration uses the entire base model; upon power-up of the processing environment the control source will be the designated default. Some combinations of enabled control sources are disallowed as they are either unnecessary or could create unintended changes.
Prog Power Up
Configuration allows the user to specify whether Operator or Program is the power-up default.
Prog Priority
Configuration allows the user to specify whether Operator or Program commands take priority when simultaneously asserted.
Automatic reset of commands
Unless specifically configured as Level, above, all commands are treated as one-shot-latched (Edge). Commands are automatically cleared when the instruction executes and processes them.
Change Destination States
Under certain configurations the destination command source for some commands may change. This is in keeping with the intent of the command. For example, if the Program state is disabled, the destination of the OCmd_Prog command becomes the Program Locked state instead of the Program state. This maintains the intent of the OCmd_Prog command: the operator entity wishes to place the function in control of the program. If the command was eliminated then there would be no way to accomplish this. This is only done in configurations where it would cause no conflict or race condition, but serves to preserve as much user functionality as is practical.
Higher Priority Command Sources
These Higher priority command sources operate independently within the model:
- External
- Override
- Maintenance
- Out-of-Service
- In-Service
- Hand
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