Motorola MCF5281, MCF5282 user manual Qadc Queue Operation with Pause

Models: MCF5282 MCF5281

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Digital Control Subsystem

The choice of single-scan or continuous-scan applies to the full queue, and is not applied to each subqueue. Once a subqueue is initiated, each CCW is executed sequentially until the last CCW in the subqueue is executed and the pause state is entered. Execution can only continue with the next CCW, which is the beginning of the next subqueue. A subqueue cannot be executed a second time before the overall queue execution has been completed.

P

000

0

0

1

0

0

0

1

0

P 0 0

BQ2

0

 

1

 

0

 

1

 

0

 

1

 

0

 

P

 

1

63

0

 

 

Conversion Command Word (CCW) Table

Beginning of Queue 1

Pause

Pause

End of Queue 1

Beginning of Queue 2

Pause

Pause

Pause

Pause

End of Queue 2

Channel Select,

Sample, Hold,

A/D Conversion

Result Word Table

00

63

Figure 27-22. QADC Queue Operation with Pause

Trigger events which occur during the execution of a subqueue are ignored, but the trigger overrun flag is set. When a continuous-scan mode is selected, a trigger event occurring after the completion of the last subqueue (after the queue completion flag is set), causes the execution to continue with the first subqueue, starting with the first CCW in the queue.

When the QADC 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 in QASR0, and a pause interrupt may be requested. The status of the queue is shown to be paused, indicating completion of a subqueue. The QADC then waits for another trigger event to again begin execution of the next subqueue.

MOTOROLA

Chapter 27. Queued Analog-to-Digital Converter (QADC)

27-39

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Motorola MCF5281, MCF5282 user manual Qadc Queue Operation with Pause