Event Handling Routine

An event handling routine for the 2TP-VME in OCCAM should look like:

-- If VME interrupts can be present at transputer boot time, initialize
-- the 2TP-VME by acknowledging these interrupts outside any event process:
intl.flag := (statusregister0 /\ #01)
WHILE (intl.flag > 0)
  SEQ
    ... acknowledge the VME interrupt
    -- reset intl.flag in statusregister0:
    statusregister0 := intl.flag
    intl.flag := (statusregister0 /\ #01)
.
.
-- Here's the actual event process:
WHILE TRUE
  event ? any
    SEQ
      event.flags := (statusregister0 /\ #3F)
      WHILE (event.flags > 0)
        SEQ
          IF
            (event.flags /\ priority1.flag) > 0
              -- This event has highest priority
              SEQ
                -- reset priority1.flag in statusregister0:
                statusregister0 := priority1.flag
                ... handle the event
            (event.flags /\ priority2.flag) > 0
              -- This event has second highest priority
              SEQ
                -- reset priority2.flag in statusregister0:
                statusregister0 := priority2.flag
                ... handle the event
            .
            .
            .
            (event.flags /\ priority.lowest.flag) > 0
              -- This event has lowest priority
              SEQ
                -- reset priority.lowest.flag in statusregister0:
                statusregister0 := priority.lowest.flag
                ... handle the event
            TRUE
              SKIP  
          event.flags := (statusregister0 /\ #3F)