MPC555
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MPC556
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
13-29
cycles of the IMB clock. It also shows that when PSL = 7, the QCLK remains low for
eight IMB clock cycles.
13.10.5 Periodic/Interval Timer
The on-chip periodic/interval timer is enabled to generate trigger events at a program-
mable interval, initiating execution of queue 1 and/or 2. The periodic/interval timer
stays reset under the following conditions:
• Queue 1 and queue 2 are programmed to any queue operating mode which does
not use the periodic/interval timer
• Interval timer single-scan mode is selected, but the single-scan enable bit is set
to zero
• IMB system reset or the master reset is asserted
• Stop mode is selected
• Freeze mode is selected
Two other conditions which cause a pulsed reset of the timer are:
• Roll-over of the timer counter
• A queue operating mode change from one periodic/interval timer mode to another
periodic/interval timer mode, depending on which queues are active in timer
mode.
NOTE
The periodic/interval timer will not reset for a queue 2 operating mode
change from one periodic/interval timer mode to another periodic/in-
terval timer mode while queue 1 is in an active periodic/interval timer
mode.
During the low power stop mode, the periodic/interval timer is held in reset. Since low
power stop mode causes QACR1 and QACR2 to be reset to zero, a valid periodic or
interval timer mode must be written after stop mode is exited to release the timer from
reset.
When the IMB internal FREEZE line is asserted 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, the freeze mode takes effect immediately, and the
timer is held in reset. When the internal FREEZE line is negated, the timer counter
starts counting from the beginning.
13.11 Interrupts
The QADC64 supports both polled and interrupt driven operation. Status bits in QASR
reflect the operating condition of each queue and can optionally generate interrupts
when enabled by the appropriate bits in QACR1 and/or QACR2.
displays the QADC64 interrupt flow.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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