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R01UH0336EJ0102 Rev.1.02
Page 271 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 7 Clock Generation
7.8.4
Functional Description
The clock monitor CLMAn is used to ensure that the frequency of a clock
(CLMAnTMON) stays between certain limits.
(1)
Detection of Abnormal Clock Frequencies
Method
1. CLMAn counts the rising edges of the monitored clock CLMAnTMON
within 16 cycles of the sampling clock CLMAnTSMP and then compares
the counter with the configured thresholds:
– CLMAnCMPL.CLMAnCMPL[11:0] defines the lower threshold.
– CLMAnCMPH.CLMAnCMPH[11:0] defines the upper threshold.
2. When CLMAnTMON stops or its frequency is too low, the counter falls
below CLMAnCMPL.CLMAnCMPL[11:0].
3. When the frequency of CLMAnTMON is too high, the counter exceeds
CLMAnCMPH.CLMAnCMPH[11:0].
In both cases, CLMAn indicates an abnormal clock frequency as described in
Section 7.8.4, (2) Indication of Abnormal Clock Frequency.
Figure 7-3
Example: f
CLMAnTMON
is low
Figure 7-4
Example: f
CLMAnTMON
is high
Note
When f
CLMAnTMON
changes within the sampling interval (16 cycles of the
CLMAnTSMP clock), the counter might be within the valid range even though
f
CLMAnTMON
has actually become too high or low.
The abnormal f
CLMAnTMON
is detected one sampling interval later.
CLMAnTMON
CLMAnCMPL.CLMAnCMPL[11:0]
CLMAnTSMP
CLMAnCMPH.CLMAnCMPH[11:0]
(1)
(2)
8
1 2 3 4 5 6 7
16
9 10 11 1213 14 15
Counter
CLMAnTMON
Counter
CLMAnCMPL.CLMAnCMPL[11:0]
CLMAnTSMP
CLMAnCMPH.CLMAnCMPH[11:0]
(1)
(3)
8
1 2 3 4 5 6 7
16
9 10 11 1213 14 15
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