Motorola MPC533 Reference Manual page 469

Only queue 2 can be in the suspended state. When a trigger event occurs on queue 1 while
queue 2 is executing, the current queue 2 conversion is aborted. The queue 2 status is
reported as suspended. Queue 2 transitions back to the active state when queue 1 becomes
idle or paused.
A trigger pending state is required since both queues cannot be active at the same time. The
status of queue 2 is changed to trigger pending when a trigger event occurs for queue 2
while queue 1 is active. In the opposite case, when a trigger event occurs for queue 1 while
queue 2 is active, queue 2 is aborted and the status is reported as queue 1 active, queue 2
suspended. So due to the priority scheme, only queue 2 can be in the trigger pending state.
There are two transition cases which cause the queue 2 status to be trigger pending before
queue 2 is shown to be in the active state. When queue 1 is active and there is a trigger
pending on queue 2, after queue 1 completes or pauses, queue 2 continues to be in the
trigger pending state for a few clock cycles. The following are fleeting status conditions:
• Queue 1 idle with queue 2 trigger pending
• Queue 1 paused with queue 2 trigger pending
Figure 13-11 displays the status conditions of the queue status field as the QADC64E goes
through the transition from queue 1 active to queue 2 active.
Figure 13-11. QADC64E Queue Status Transition
The queue status field is affected by the stop mode. Because all of the analog logic and
control registers are reset, the queue status field is reset to queue 1 idle, queue 2 idle.
During the freeze mode, the queue status field is not modified. The queue status field retains
the status it held prior to freezing. As a result, the queue status can show queue 1 active,
queue 2 idle, even though neither queue is being executed during freeze.
MOTOROLA Chapter 13. Queued Analog-to-Digital Converter Legacy Mode Operation
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Queue 1
Active
Active
Idle (Paused)
Idle (Paused)
Programming the QADC64E Registers
Queue 2
Idle
Trigger Pending
Trigger Pending
Active
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