MPC555
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MPC556
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
13-18
Another pause and end-of-queue boundary condition occurs when the pause and an
end-of-queue condition occur in the same CCW. Both the pause and end-of-queue
conditions are recognized simultaneously. The end-of-queue condition has prece-
dence so a conversion is not performed for the CCW and the pause flag is not set. The
QADC64 sets the completion flag and the queue status becomes idle. Examples of
this situation are:
• The pause bit is set in CCW0 and EOQ is programmed into CCW0
• During queue 1 operation, the pause bit is set in CCW20, which is also BQ2
13.10.3 Scan Modes
The QADC64 queuing mechanism provides several methods for automatically scan-
ning input channels. In single-scan mode, a single pass through a sequence of con-
versions defined by a queue is performed. In continuous-scan mode, multiple passes
through a sequence of conversions defined by a queue are executed. The possible
modes are:
• Disabled and reserved mode
• Software initiated single-scan mode
• External trigger single-scan mode
• External gated single-scan mode (queue 1 only)
• Interval timer single-scan mode
• Software initiated continuous-scan mode
• External trigger continuous-scan mode
• External gated continuous-scan mode (queue 1 only)
• Interval timer continuous-scan mode
The following paragraphs describe the disabled/reserved, single-scan, and continu-
ous-scan operations.
13.10.3.1 Disabled Mode
When the disabled mode is selected, the queue is not active. Trigger events cannot
initiate queue execution. When both queue 1 and queue 2 are disabled, wait states are
not encountered for IMB accesses of the RAM. When both queues are disabled, it is
safe to change the QCLK prescaler values.
13.10.3.2 Reserved Mode
Reserved mode allows for future mode definitions. When the reserved mode is select-
ed, the queue is not active.
CAUTION
Do not use a reserved mode. Unspecified operations may result.
13.10.3.3 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:
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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