MCF5282CVM66 Datasheet, PDF (576/766 Pages) Freescale Semiconductor, Inc – MCF5282 and MCF5216 ColdFire® Microcontroller User’s Manual

Queued Analog-to-Digital Converter (QADC)
The first three examples in Figure 28-23 through Figure 28-25 (S1, S2, and S3) show what happens when
a new trigger event is recognized before the queue has completed servicing the previous trigger event on
the same queue.
In situation S1 (Figure 28-23), one trigger event is being recognized on each queue while that queue is still
working on the previously recognized trigger event. The trigger overrun error status bit is set, and the
premature trigger event is otherwise ignored. A trigger event that occurs before the servicing of the
previous trigger event is through does not disturb the queue execution in progress.
T1 T1
Q1: C1 C2 C3 C4
TOR1
CF1
T2
T2
Q2: _{C1 C2 C3 C4}
Q1:
IDLE
ACTIVE
TOR2 CF2
IDLE
Q2:
IDLE
ACTIVE
IDLE
QS:
0000
1000
0000
0010
0000
Figure 28-23. CCW Priority Situation 1
In situation S2 (Figure 28-24), more than one trigger event is recognized before servicing of a previous
trigger event is complete. The trigger overrun bit is again set, but the additional trigger events are otherwise
ignored. After the queue is complete, the first newly detected trigger event causes queue execution to begin
again. When the trigger event rate is high, a new trigger event can be seen very soon after completion of
the previous queue, leaving little time to retrieve the previous results. Also, when trigger events are
occurring at a high rate for queue 1, the lower priority queue 2 channels may not get serviced at all.
T1 T1 T1 T1
T1
Q1: C1 C2 C3 C4
C1 C2 C3 C4
TOR1 TOR1 TOR1 CF1
CF1
T2
T2 T2
Q2: C1 C2 C3 C4
TOR2 TOR2 CF2
Q1: ^IDLE
ACTIVE
IDLE
ACTIVE
IDLE
Q2:
IDLE
ACTIVE
IDLE
QS:
1000
1000
0000
0010
0000
Figure 28-24. CCW Priority Situation 2
Situation S3 (Figure 28-25) shows that when the pause feature is used, the trigger overrun error status bit
is set the same way and that queue execution continues unchanged.
28-38
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Freescale Semiconductor