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MPC565/MPC566 Reference Manual
MOTOROLA
Digital Subsystem
cannot be executed a second time before the overall queue execution has been completed.
Trigger events which occur during the execution of a sub-queue are ignored, except that the
trigger overrun flag is set. When a continuous-scan mode is selected, a trigger event
occurring after the completion of the last sub-queue (after the queue completion flag is set),
causes the execution to continue with the first sub-queue, starting with the first CCW in the
queue.
When the QADC64E encounters a CCW with the pause bit set, the queue enters the paused
state after completing the conversion specified in the CCW with the pause bit. The pause
flag is set and a pause software interrupt may optionally be issued. The status of the queue
is shown to be paused, indicating completion of a sub-queue. The QADC64E then waits for
another trigger event to again begin execution of the next sub-queue.
13.4.3 Boundary Conditions
The following are queue operation boundary conditions:
The first CCW in a queue contains channel 63 or 127, the end-of-queue (EOQ) code.
The queue becomes active and the first CCW is read. The end-of-queue is
recognized, the completion flag is set, and the queue becomes idle. A conversion is
not performed.
BQ2 (beginning of queue 2) is set at the end of the CCW table (63 or 127) and a
more information on BQ2. The end-of-queue condition is recognized, a conversion
is performed, the completion flag is set, and the queue becomes idle.
BQ2 is set to CCW0 and a trigger event occurs on queue 1. After reading CCW0,
the end-of-queue condition is recognized, the completion flag is set, and the queue
becomes idle. A conversion is not performed.
BQ2 is set beyond the end of the CCW table (64 – 127) and a trigger event occurs
on queue 2. The end-of-queue condition is recognized immediately, the completion
flag is set, and the queue becomes idle. A conversion is not performed.
NOTE
Multiple
end-of-queue
conditions
may
be
recognized
simultaneously, although there is no change in the QADC64E
behavior. For example, if BQ2 is set to CCW0, CCW0 contains
the EOQ code, and a trigger event occurs on queue 1, the
QADC64E reads CCW0 and detects both end-of-queue
conditions. The completion flag is set and queue 1 becomes
idle.
Boundary conditions also exist for combinations of pause and end-of-queue. One case is
when a pause bit is in one CCW and an end-of-queue condition is in the next CCW. The
conversion specified by the CCW with the pause bit set completes normally. The pause flag