H8SXSLASH1663M datasheet(882/1504 Pages) RENESAS

882 / 1504 page

Section 17 32K Timer (TM32K)

Rev. 2.00 Sep. 24, 2008 Page 850 of 1468

REJ09B0412-0200

17.3.2

EXCKSN=1 Operation

When the EXCKSN bit in TCR32K is 1, the timer counter operates as an 8-bit counter.

Every time the value in TCNT32K1 reaches H'FF, a 32KOVI interrupt is generated. By setting the

CKS1 and CKS0 bits in TCR32K, intervals of 250ms, 500ms, 1s, and 2s between interrupts are

selectable.

H'FF

H'00

32KOVI

Time

32KOVI

32KOVI: 32K timer interrupt

32KOVI

Overflow

TCNT32K value

3 clocks of 32K

Overflow

TME = 1

Figure 17.2 EXCKSN = 1 32K Timer Operation

17.3.3

EXCKSN=0 Operation

When the EXCKSN bit in TCR32K is 0, the timer counter operates as a 24-bit counter. The lower-

order 8-bits are TCNT32K3, which operates as a free-running up-counter that counts from H'00 to

H'3B. The higher-order 16-bits in TCNT32K1 and TCNT32K2 act as an up-counter that counts

the number of times TCNT32K3=H'3B. Generation of the 32KOVI interrupt either for all values

with TCNT32K3=H'3B or when TCNT32K1 to TCNT32K3=H'FFFF3B can be selected by the

setting of the CKS1 bit. This setting in combination with the setting of the CKS0 bit can be used

to se the interrupt interval to 30s, 60s. approx. 22.7 days, or approx. 45.5 days

When the EXCKSN bit is 0, the CKS1 bit can be changed while the timer counter is operating

because the TME bit is 1. This allows variation of the 32KOV1 interrupt interval while the timer

counter is in operation. When the value of the CKS1 bit is from 0 to 1, the higher-order 16-bit

counter (TCNT32K1, TCNT32K2) resumes counting after being initialized to H'00_00.

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