MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
943
Preliminary—Subject to Change Without Notice
Figure 23-76. Worst-Case Latency for Channel 0 (Second Try)
Conclusion: with this system configuration, the WCL of both channel 0 and channel 1 is 3.85 ms, which
is within the limit of 4 ms needed for a 50-kHz PWM.
Next, find the WCL for channel 2. Assume channel 2 has just finished service. Map the channels in the
H-M-H-L-H-M-H sequence. See
.
Figure 23-77. Worst-Case Latency for Channel 2
Conclusion: with this system configuration, the WCL for channels 2 and 8 is 4.7 ms, which is within the
40 and 80 ms WCL requirements.
Notice that channels 2 and 8 are well within their WCL requirements. The system could be reconfigured
as shown in
to give channels 0 and 1 a larger margin while still keeping channels 2, 8 and 15
within their WCL requirements.
Table 23-108. Second-Try System with Channel 0 and 1 Reconfigured
Channel
Priority
Function
1
,
2
1
0% RAM collision rate
0
High
PWM at 50 kHz (needs a 10-
μ
s WCL)
1
High
PWM at 50 kHz (needs a 10-
μ
s WCL)
2
Middle
PWM at 5 kHz (needs a 40-
μ
s WCL)
8
Low
PPWA at 5 kHz (needs a 80-
μ
s WCL)
15
Low
DIO as input at rate of 1 ms
TPU CH0 WCL TIM 2
TPU CH0 WCL TIM 2
= 10-CYCLE TIME SLOT TRANSITION
= 4-CYCLE NOP INSTRUCTION
CHANNEL 0
SERVICED
WORST CASE LATENCY
H
M
H
L
H
M
H
H
CHANNEL 2
OR CHANNEL
SERVICED
CHANNEL 1
SERVICED
CHANNEL 15
SERVICED
CHANNEL 0
SERVICED
M
H
L
TPU CH2 WCL TIM 1
TPU CH2 WCL TIM 1
= 10-CYCLE TIME SLOT TRANSITION
= 4-CYCLE NOP INSTRUCTION
CHANNEL 2
SERVICED
WORST CASE LATENCY
H
M
H
L
H
M
H
H
CHANNEL 0
SERVICED
CHANNEL 15
SERVICED
CHANNEL 1
SERVICED
CHANNEL 8
SERVICED
M
H
L
CHANNEL 2
SERVICED