Microcontroller User's Manual

27-42 MCF5282 User’s Manual MOTOROLA
Digital Control Subsystem
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.
Figure 27-24. CCW Priority Situation 2
Situation S3 (Figure 27-25) 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.
Figure 27-25. CCW Priority Situation 3
The next two situations consider trigger events that occur for the lower priority queue 2,
while queue 1 is actively being serviced.
Situation S4 (Figure 27-26) shows that a queue 2 trigger event is recognized while queue 1
is active is saved, and as soon as queue 1 is finished, queue 2 servicing begins.
T1
ACTIVE IDLE
Q1:
Q2:
QS:
IDLE
ACTIVE
IDLE
ACTIVE IDLE
1000 1000 0000 0010
0000
C1 C2 C3 C4
TOR2
T2 T2
Q2:
CF2
IDLE
C1 C2 C3 C4
T1
CF1
C1 C2 C3 C4
TOR1
T1
Q1:
CF1
TOR1
T1
TOR1
T1
TOR2
T2
PAUSE
Q1:
Q2:
QS:
IDLE
ACTIVE
IDLE
ACTIVE IDLE
1000 0110 0001 0010
ACTIVE
0000
IDLE
C1 C2
T1 T1
Q1:
TOR1 PF1
C1 C2
0000
Q2:
0100
TOR2 PF2
T2 T2
0101
C3 C4
T1 T1
TOR1 CF1
ACTIVE
PAUSE
1001
C3 C4
CF2
T2 T2
TOR2