MMC2114 MOTOROLA [Motorola, Inc], MMC2114 Datasheet - Page 502

• Manufacturer Part Number: MMC2114
• Description: M CORE Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

Queued Analog-to-Digital Converter (QADC)
19.10.7.4 Periodic Timer Continuous-Scan Mode
Advance Information
502
The purpose of externally gated continuous-scan mode is to
continuously collect digitized samples while the gate is open and to have
the most recent samples available. It is up to the programmer to ensure
that the gate is not opened so long that an end-of-queue is reached.
In the event that the queue completes before the gate closes, the CF1
flag will set, and the queue will roll over to the beginning and continue
conversions until the gate closes. If the gate remains open and the CF1
flag is not cleared, when the queue completes a second time the TOR1
flag will set and the queue will roll-over again. The queue will continue to
execute until the gate closes or the mode is disabled.
If the gate closes before queue 1 completes execution, the QADC stops
and sets the PF1 bit to indicate an incomplete queue. The CWPQ1 field
can be read to determine the last valid conversion in the queue. If the
gate opens again, execution of queue 1 restarts. The start of queue 1 is
always the first CCW in the CCW table. The condition of the gate is only
sampled after each conversion during queue execution, so closing the
gate for a period less than a conversion time interval does not guarantee
the closure will be captured.
The QADC includes a dedicated periodic timer for initiating a scan
sequence on queue 1 and/or queue 2. A programmable timer interval
ranging from 2
selected. The QCLK period is prescaled down from the MCU clock.
When a periodic timer continuous-scan mode is selected, the timer
begins counting. After the programmed interval elapses, the timer
generated trigger event starts the appropriate queue. The QADC
automatically performs the conversions in the queue until an
end-of-queue condition or a pause is encountered. When a pause
occurs, the QADC waits for the periodic interval to expire again, then
continues with the queue. Once EOQ has been detected, the next trigger
event causes queue execution to restart with the first CCW in the queue.
The periodic timer generates a trigger event whenever the time interval
elapses. The trigger event may cause queue execution to continue
following a pause or queue completion or may be considered a trigger
Freescale Semiconductor, Inc.
For More Information On This Product,
Queued Analog-to-Digital Converter (QADC)
Go to: www.freescale.com
7
to 2
17
times the QCLK period in binary multiples can be
MMC2114 • MMC2113 • MMC2112 — Rev. 1.0
MOTOROLA