H8S2245 datasheet(433/818 Pages) RENESAS

433 / 818 page

Section 11 Watchdog Timer

Rev.3.00 Mar. 26, 2007 Page 391 of 772

REJ09B0355-0300

Bit 7—Overflow Flag (OVF): Indicates that TCNT has overflowed from H'FF to H'00, when in

interval timer mode. This flag cannot be set during watchdog timer operation.

Bit 7

OVF

Description

[Clearing condition]

Cleared by reading TCSR when OVF = 1, then writing 0 to OVF*

(Initial value)

[Setting condition]

Set when TCNT overflows (changes from H'FF to H'00) in interval timer mode

Note:

When OVF is polled and the interval timer interrupt is disabled, OVF = 1 must be read

at least twice.

Bit 6—Timer Mode Select (WT/

IT): Selects whether the WDT is used as a watchdog timer or

interval timer. If used as an interval timer, the WDT generates an interval timer interrupt request

(WOVI) when TCNT overflows. If used as a watchdog timer, the WDT generates the

WDTOVF

signal when TCNT overflows.

Bit 6

WT/

Description

Interval timer: Sends the CPU an interval timer interrupt request (WOVI)

when TCNT overflows

(Initial value)

Watchdog timer: Generates the

WDTOVF signal when TCNT overflows*

Note:

For details of the case where TCNT overflows in watchdog timer mode, see section

11.2.3, Reset Control/Status Register (RSTCSR).

Bit 5—Timer Enable (TME): Selects whether TCNT runs or is halted.

Bit 5

TME

Description

TCNT is initialized to H'00 and halted

(Initial value)

TCNT counts

Bits 4 and 3—Reserved: Read-only bits, always read as 1.

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