Motorola ColdFire MCF5281 - Manual (Page 591)

Queued Analog-to-Digital Converter (QADC)
Freescale Semiconductor 28-53
• Both queue 1 and queue 2 are programmed to any mode which does not use the periodic/interval
timer.
• System reset is asserted.
• Stop mode is enabled.
• Debug mode is enabled.
NOTE
Interval timer single-scan mode does not start the periodic/interval timer
until the single-scan enable bit is set.
These conditions will cause a pulsed reset of the periodic/interval timer during use:
• A queue 1 operating mode change to a mode which uses the periodic/interval timer, even if queue
2 is already using the timer
• A queue 2 operating mode change to a mode which uses the periodic/interval timer, provided queue
1 is not in a mode which uses the periodic/interval timer
• Roll over of the timer
During stop mode, the periodic/interval timer is held in reset. Because stop mode causes QACR1 and
QACR2 to be reset to 0, a valid periodic or interval timer mode must be written after leaving stop mode to
release the timer from reset.
When QADC debug mode is entered and a periodic or interval timer mode is selected, the timer counter
is reset after the conversion in progress completes. When the periodic or interval timer mode has been
enabled (the timer is counting), but a trigger event has not been issued, debug mode takes effect
immediately, and the timer is held in reset. Removal of the QADC debug condition restarts the counter
from the beginning. Refer to
Section 28.3.1, “Debug Mode for more information.
28.8.10 Conversion Command Word Table
The conversion command word (CCW) table is 64 half-word (128 byte) long RAM with 10 bits of each
entry implemented. The CCW table is written by the user and is not modified by the QADC. Each CCW
requests the conversion of one analog channel to a digital result. The CCW specifies the analog channel
number, the input sample time, and whether the queue is to pause after the current CCW. The 10
implemented bits of the CCW can be read and written. The remaining six bits are unimplemented and read
as 0s; write operations have no effect. Each location in the CCW table corresponds to a location in the
result word table. When a conversion is completed for a CCW entry, the 10-bit result is written in the
corresponding result word entry.
The beginning of queue 1 is the first location in the CCW table. The first location of queue 2 is specified
by the beginning of queue 2 pointer field (BQ2) in QACR2. To dedicate the entire CCW table to queue 1,
place queue 2 in disabled mode and write BQ2 to 64 or greater. To dedicate the entire CCW table to queue
2, place queue 1 in disabled mode and set BQ2 to the first location in the CCW table (CCW0).
Figure 28-43 illustrates the operation of the queue structure.
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3