Motorola MPC533 Reference Manual page 485

13.5.4.2 Reserved Mode
Reserved mode allows for future mode definitions. When the reserved mode is selected, the
queue is not active. It functions the same as disabled mode.
Do not use a reserved mode. Unspecified operations may
result.
13.5.4.3 Single-Scan Modes
When the application software wants to execute a single pass through a sequence of
conversions defined by a queue, a single-scan queue operating mode is selected. By
programming the MQ field in QACR1 or QACR2, the following modes can be selected:
• Software initiated single-scan mode
• External trigger single-scan mode
• External gated single-scan mode
• Periodic/Interval timer single-scan mode
Queue 2 cannot be programmed for external gated single-scan
mode.
In all single-scan queue operating modes, the software must also enable the queue to begin
execution by writing the single-scan enable bit to a one in the queue's control register. The
single-scan enable bits, SSE1 and SSE2, are provided for queue 1 and queue 2 respectively.
Until the single-scan enable bit is set, any trigger events for that queue are ignored. The
single-scan enable bit may be set to a one during the write cycle, which selects the
single-scan queue operating mode. The single-scan enable bit is set through software, but
will always read as a zero. Once set, writing the single-scan enable bit to zero has no effect.
Only the QADC64E can clear the single-scan enable bit. The completion flag, completion
interrupt, or queue status are used to determine when the queue has completed.
After the single-scan enable bit is set, a trigger event causes the QADC64E to begin
execution with the first CCW in the queue. The single-scan enable bit remains set until the
queue is completed. After the queue reaches completion, the QADC64E resets the
single-scan enable bit to zero. If the single-scan enable bit is written to a one or a zero by
the software before the queue scan is complete, the queue is not affected. However, if the
software changes the queue operating mode, the new queue operating mode and the value
of the single-scan enable bit are recognized immediately. The conversion in progress is
aborted and the new queue operating mode takes effect.
In the software-initiated single-scan mode, the writing of a one to the single-scan enable bit
causes the QADC64E to internally generate a trigger event and the queue execution begins
MOTOROLA Chapter 13. Queued Analog-to-Digital Converter Legacy Mode Operation
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
CAUTION
NOTE
Digital Subsystem
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