
Filters:

Pre filter:

Entry: (Task paged in)
      R0 - Tasks's event mask (may be modified by filter).
      R2 - Task handle of calling task.
     
Exit:
      R0 - New event mask to use.
      All other registers preserved. 


Post filter:

Entry:  (Task paged in)

      R0 - Event
      R1 - Pointer to block
      R2 - Task handle of receiving task.

Exit:

      R0   - New event code.
      [R1] - Data for new event.
      
      R2,R3 preserved.
      