Ccw Priority Situation 2; Ccw Priority Situation 3 - Motorola ColdFire MCF5281 User Manual

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.
T1 T1 T1
C1 C2
Q1:
TOR1 TOR1
IDLE ACTIVE
Q1:
Q2:
1000
QS:
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.
T1 T1
C1
Q1:
TOR1
ACTIVE
IDLE
Q1:
IDLE
Q2:
QS:
0000 1000
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.
27-42
T1 T1
C3 C4 C1 C2
TOR1 CF1
IDLE ACTIVE
IDLE
1000
Figure 27-24. CCW Priority Situation 2
C2
T2 T2
PF1
Q2:
C1 C2
TOR2 PF2
PAUSE
ACTIVE
0100 0110
Figure 27-25. CCW Priority Situation 3
MCF5282 User's Manual
T2
C3 C4
Q2:
CF1
0000
T1 T1
C3 C4
TOR1 CF1
ACTIVE
PAUSE
0101 1001 0001
T2 T2
C1 C2 C3 C4
TOR2 TOR2
CF2
IDLE
ACTIVE IDLE
0010 0000
T2 T2
C3 C4
CF2
TOR2
IDLE
ACTIVE IDLE
0010 0000
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