Enable Unit Control Tags for a Selected Unit

You can enable the particular Unit Control tags for the selected unit. This capability provides individual control over each unit in the process. Two Hold Propagation Modes are available. In addition to the Hold Propagation modes, Unit Control can be further enhanced by using Unit State system tags.

To enable unit control tags for a selected unit

1. Open the Equipment Allocation dialog box.

2. Click the appropriate Unit Control button.

   Note: Hold Propagation Mode 1 is enabled by default. To enable Hold Propagation Mode 2, you must enable the Phase/Batch Status parameter name using Environment Editor. To use Unit State system tags, you must enable the Unit States parameter using Environment Editor.

Hold Propagation Mode 1 - Unit State Enabled

This mode is the default mode of operation and enables a unit to be allocated only if it is Unallocated, has an Available Status, and has a Ready state. During normal processing, if unit state goes to Alarm or Held or if the batch is held by the operator, Unit Hold is set for all units allocated by the batch. The batch state goes to Held when all allocated units transition to either the Held or the Alarm state. The operator can restart the batch only if all allocated units are in the Held state. If any units are in the Alarm state, they must transition to the Held state before the batch Restart command is available. After a Restart command is written and all allocated units transition to either the Run or Ready state, the batch status returns to Run.

Note: There is an assumption that a Unit in a Held state can be restarted and then immediately change to a Run or Alarm state. If this mode does not appear to function as described, you should review the Restart logic that you are using.

Hold Propagation Mode 1 - Unit State Disabled

This mode enables unit allocation only if it is Unallocated and has an Available status. During normal processing, if the batch is held by the operator, Unit Hold is set for all units allocated by the batch. The batch state goes to Held. The operator can restart at any time. After a Restart command is written the batch status returns to Run.

Hold Propagation Mode 2 - Unit State Enabled

This mode enables unit allocation only if it is Unallocated, has an Available Status, and has a Ready state. During normal processing, if the unit state changes to Alarm or Held, or if any phase changes status from Run to Held, or if the batch is placed in Held by the operator, then Unit Hold is set for all units allocated by the batch. Additionally, the phase Hold is set for all phase with a Run status. The batch state goes to Held when all allocated units transition to either the Held or the Alarm state. The operator can restart the batch only if all allocated units are in the Held state. If any units are in the Alarm state, they must transition to the Held state before the batch Restart command is available. After a Restart command is written and all allocated units transition to either the Run or Ready state, the batch status returns to Run.

Hold Propagation Mode 2 - Unit State Disabled

This mode enables unit allocation only if it is Unallocated and has an Available status. During normal processing, if any running phase changes to Held, or if the batch is held by the operator, Unit Hold is set for all units allocated by the batch and Hold is set for all running phases. The batch state goes to Held. The operator can restart the batch at any time. After a Restart command is written the batch status returns to Run.

Note: There is an assumption that a Unit in a Held state can be restarted and immediately change to a Run or Alarm state. If this mode does not appear to function as described, you should review the Restart logic that you are using.

For additional information, see "Allocating Equipment for a Batch".