Figure 9.4 Free-Running Counter Operation - Renesas H8SX/1500 Series Hardware Manual

Section 9 16-Bit Timer Pulse Unit (TPU)
(b) 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 (changes 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 9.4 illustrates free-running counter operation.
TCNT value
H'FFFF
H'0000
CST bit
TCFV
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 count-up operation as
a 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 9.5 illustrates periodic counter operation.
Rev. 3.00 Mar. 14, 2006 Page 300 of 804
REJ09B0104-0300

Figure 9.4 Free-Running Counter Operation

Time