H8SSLASH2214 datasheet(453/936 Pages) RENESAS

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Section 10 16-Bit Timer Pulse Unit (TPU)

Rev.4.00 Sep. 18, 2008 Page 393 of 872

REJ09B0189-0400

• 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.

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