Renesas ZTAT H8S/2357F, Hardware Manual

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Rev.6.00 Oct.28.2004 page 373 of 1016
REJ09B0138-0600H
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Free-running count operation and periodic count operation
Immediately after a reset, the TPU’s TCNT counters are all designated as free-running counters. When the relevant bit
in TSTR is set to 1 the corresponding TCNT counter starts up-count operation as a free-running counter. When TCNT
overflows (from H'FFFF to H'0000), the TCFV bit in TSR is set to 1. If the value of the corresponding TCIEV bit in
TIER is 1 at this point, the TPU requests an interrupt. After overflow, TCNT starts counting up again from H'0000.
Figure 10-7 illustrates free-running counter operation.
TCNT value
H'FFFF
H'0000
CST bit
TCFV
Time
Figure 10-7 Free-Running Counter Operation
When compare match is selected as the TCNT clearing source, the TCNT counter for the relevant channel performs
periodic count operation. The TGR register for setting the period is designated as an output compare register, and
counter clearing by compare match is selected by means of bits CCLR2 to CCLR0 in TCR. After the settings have
been made, TCNT starts up-count operation as periodic counter when the corresponding bit in TSTR is set to 1. When
the count value matches the value in TGR, the TGF bit in TSR is set to 1 and TCNT is cleared to H'0000.
If the value of the corresponding TGIE bit in TIER is 1 at this point, the TPU requests an interrupt. After a compare
match, TCNT starts counting up again from H'0000.
Figure 10-8 illustrates periodic counter operation.
TCNT value
TGR
H'0000
CST bit
TGF
Time
Counter cleared by TGR
compare match
Flag cleared by software or
DTC/DMAC activation
Figure 10-8 Periodic Counter Operation