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Section 17 Compare Match Timer (CMT)
Rev. 4.00 Sep. 14, 2005 Page 514 of 982
REJ09B0023-0400
17.4 Compare Matches
17.4.1 Timing of Compare Match Flag Setting
When CMCOR and CMCNT match, a compare match signal is generated and the CMF bit in
CMCSR is set to 1. The compare match signal is generated in the last state in which the values
match (when the CMCNT value is updated to H'0000). That is, after a match between CMCOR
and CMCNT, the compare match signal is not generated until the next CMCNT counter clock
input. Figure 17.4 shows the timing of CMF bit setting.
N
Peripheral operating
clock (Pφ)
Counter clock
CMCNT
CMCOR
Compare match
signal
Clock
N + 1
N
0
Figure 17.4 Timing of CMF Setting
17.4.2 DMA Transfer Requests and Interrupt Requests
Generation of a DMA transfer request or an interrupt request when a compare match occurs can be
selected with bits CMR1 and CMR0 in CMCSR.
With a DMA transfer request, the request signal is cleared automatically when the DMAC accepts
the request. However, the CMF bit in CMCSR is not cleared to 0.
An interrupt request is cleared by writing 0 to the CMF bit in CMCSR. Therefore, an operation to
set CMF = 0 must be performed by the user in the exception handling routine. If this operation is
not carried out, another interrupt will be generated.