Motorola ColdFire MCF5281 - Manual (Page 573)

Queued Analog-to-Digital Converter (QADC)
Freescale Semiconductor 28-35
completion or the paused state, queue 2 begins executing again. The programming of the RESUME
bit in QACR2 determines which CCW is executed in queue 2.
• When simultaneous trigger events occur for queue 1 and queue 2, queue 1 begins execution and
the queue 2 status is changed to trigger pending.
• When subqueues are paused
The pause feature can be used to divide queue 1 and/or queue 2 into multiple subqueues. A subqueue is
defined by setting the pause bit in the last CCW of the subqueue.
Figure 28-22 shows the CCW format and an example of using pause to create subqueues. Queue 1 is
shown with four CCWs in each subqueue and queue 2 has two CCWs in each subqueue.
The operating mode selected for queue 1 determines what type of trigger event causes the execution of
each of the subqueues within queue 1. Similarly, the operating mode for queue 2 determines the type of
trigger event required to execute each of the subqueues within queue 2.
For example, when the external trigger rising edge continuous-scan mode is selected for queue 1, and there
are six subqueues within queue 1, a separate rising edge is required on the external trigger signal after
every pause to begin the execution of each subqueue (refer to
Figure 28-22 ).
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.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3