R8CSLASH20 datasheet(459/501 Pages) RENESAS

459 / 501 page

R8C/20 Group, R8C/21 Group

21. Usage Notes

Rev.2.00 Aug 27, 2008

Page 443 of 458

REJ09B0250-0200

21.3.4

Notes on Timer RE

21.3.4.1

Starting and Stopping Count

Timer RE has the TSTART bit for instructing count start or stop, and the TCSTF bit which indicates count start

or stop. The TSTART and TCSTF bits are in the TRECR1 register.

Timer RE starts counting when setting the TSTART bit to 1 (count starts) and the TCSTF bit is set to 1 (count

starts). It takes the time for up to 2 cycles of the count source until the TCSTF bit is set to 1 after setting the

TSTART bit to 1. During this time, do not access registers associated with Timer RE(1) other than the TCSTF

bit.

Also, timer RE stops counting when setting the TSTART bit to 0 (count stops) and the TCSTF bit is set to 0

(count stops). It takes the time for up to 2 cycles of the count source until the TCSTF bit is set to 0 after setting

the TSTART bit to 0. During this time, do not access registers associated with timer RE other than the TCSTF

bit.

NOTE:

1. Registers associated with Timer RE:TRESEC, TREMIN, TRECR1, TRECR2, TRECSR

21.3.4.2

Write to the following registers or bits while timer RE stops.

• TRESEC and TRECR2 registers

• The INT bit in TRECR1 register

• RCS0 to RCS2 bits in TRECSR register

The state while Timer RE stops is indicated as the state where the TSTART and TCSTF bits in the TRECR1

Also, set all above-mentioned registers and bits (immediately before timer RE count starts) before setting the

TRECR2 register.

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