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Section 17 Compare Match Timer (CMT)
Rev. 4.00 Sep. 14, 2005 Page 513 of 982
REJ09B0023-0400
17.3 Operation
17.3.1 Interval Count Operation
When an internal clock is selected with the CKS1 and CKS0 bits in CMCSR and the STR bit in
CMSTR is set to 1, CMCNT starts incrementing using the selected clock. When the values in
CMCNT and CMCOR match, CMCNT is cleared to H'0000 and the CMF flag in CMCSR is set to
1. CMCNT then starts counting up again from H'0000.
Figure 17.2 shows the operation of the compare match counter.
CMCOR
H'0000
CMCNT value
Time
Counter cleared by compare
match with CMCOR
Figure 17.2 Counter Operation
17.3.2 CMCNT Count Timing
One of four internal clocks (Pφ/4, Pφ/8, Pφ/16, and Pφ/64) obtained by dividing the Pφ clock can
be selected with bits CKS1 and CKS0 in CMCSR. Figure 17.3 shows the timing.
Peripheral operating
clock (Pφ)
Clock
N
Clock
N + 1
Internal clock
Count clock
CMCNT
N
N + 1
Figure 17.3 Count Timing