H8SSLASH2225 datasheet(485/1071 Pages) RENESAS

485 / 1071 page

Section 11 16-Bit Timer Pulse Unit (TPU)

Rev. 5.00 Aug 08, 2006 page 399 of 982

REJ09B0054-0500

2. 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 11.4 illustrates free-running counter operation.

TCNT value

H'FFFF

H'0000

CST bit

TCFV

Time

Figure 11.4 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

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 11.5 illustrates periodic counter operation.

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