MMC2107 Datasheet, PDF (469/618 Pages) –

Freescale Semiconductor, Inc.
Queued Analog-to-Digital Converter (QADC)
Digital Control
internally generate and act on a trigger event is very short, software can
momentarily read the status conditions, indicating that the queue is
paused. The trigger overrun flag is never set while in the
software-initiated single-scan mode.
The software-initiated single-scan mode is useful in these applications:
• Allows software complete control of the queue execution
• Allows the software to easily alternate between several queue
sequences
18.10.6.2 External Trigger Single-Scan Mode
The external trigger single-scan mode is available on both queue 1 and
queue 2. The software programs the polarity of the external trigger edge
that is to be detected, either a rising or a falling edge. The software must
enable the scan to occur by setting the single-scan enable bit for the
queue.
The first external trigger edge causes the queue to be executed one
time. Each CCW is read and the indicated conversions are performed
until an end-of-queue condition is encountered. After the queue is
completed, the QADC clears the single-scan enable bit. Software may
set the single-scan enable bit again to allow another scan of the queue
to be initiated by the next external trigger edge.
The external trigger single-scan mode is useful when the input trigger
rate can exceed the queue execution rate. Analog samples can be taken
in sync with an external event, even though the software is not interested
in data taken from every edge. The software can start the external trigger
single-scan mode and get one set of data, and at a later time, start the
queue again for the next set of samples.
When a pause bit is encountered during external trigger single-scan
mode, another trigger event is required for queue execution to continue.
Software involvement is not needed to enable queue execution to
continue from the paused state.
MMC2107 – Rev. 2.0
MOTOROLA
Queued Analog-to-Digital Converter (QADC)
For More Information On This Product,
Go to: www.freescale.com
Technical Data
469