MMC2107 - Freescale Semiconductor

Freescale Semiconductor, Inc.
Queued Analog-to-Digital Converter (QADC)
Register Descriptions
QUEUE 1
QUEUE 2
ACTIVE
IDLE
ACTIVE
TRIGGER PENDING
IDLE (PAUSED)
TRIGGER PENDING
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Freescale Semiconductor, I
IDLE (PAUSED)
ACTIVE
Figure 18-12. Queue Status Transition
CWP[5:0] — Command Word Pointer Field
The CWP allows the software to know which CCW is executing at
present, or was last completed. The command word pointer is a
software read-only field, and write operations have no effect. The
CWP allows software to monitor the progress of the QADC scan
sequence. The CWP field is a CCW word pointer with a valid range of
0 to 63.
When a queue enters the paused state, the CWP points to the CCW
with the pause bit set. While in pause, the CWP value is maintained
until a trigger event occurs on the same queue or the other queue.
Usually, the CWP is updated a few clock cycles before the queue
status field shows that the queue has become active. For example,
software may read a CWP pointing to a CCW in queue 2, and the
status field shows queue 1 paused, queue 2 trigger pending.
When the QADC finishes the scan of the queue, the CWP points to
the CCW where the end-of-queue condition was detected. Therefore,
when the end-of-queue condition is a CCW with the EOQ code
(channel 63), the CWP points to the CCW containing the EOQ.
When the last CCW in a queue is in the last CCW table location
(CCW63), and it does not contain the EOQ code, the end-of-queue is
detected when the following CCW is read, so the CWP points to word
CCW0.
Finally, when queue 1 operation is terminated after a CCW is read
that is defined as BQ2, the CWP points to the same CCW as BQ2.
MMC2107 – Rev. 2.0
Technical Data
MOTOROLA Queued Analog-to-Digital Converter (QADC) 435
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