Unit Status

The following figure shows the unit block interface between AVEVA Batch Management System and the control system logic. Note that there is no Start control signal as there is for phases in the Phase Block Control State Diagram.

Before allocating a unit, AVEVA Batch Management System checks the unit status. If it is an acceptable value, it allocates the unit.

On Batch Clients, when a batch (not a phase) Hold, Restart, or Abort action initiates, the Batch Manager sends the corresponding unit control signal to all the units allocated for the corresponding batch. The Batch Manager does not verify that these unit control signals are used.

Control system logic sets the unit status, which is monitored by the Batch Manager for a satisfactory status before allocating the particular unit. During batch processing, the Batch Manager sends batch status information (Run, Held, and Aborting) to all of the unit blocks associated with the batch.

Batch Manager generates unexpected status error messages during phase logic processing if the status change is against the rules for phase logic. For example, if the phase status goes from Held to Ready. These messages are not generated for the following scenarios:

• A unit is not allocated, has an Available status, but has Run, Held, or Alarm state.

• A unit state goes to Ready while phases for that unit are still active.

  Caution: Use caution when you create unit control and state control logic to ensure that these improper state transitions do not occur.