Datasheet

Table Of Contents
Section 12 Watchdog Timer (WDT)
Page 370 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
12.2 Register Descriptions
The WDT has the following three registers. For details, refer to section 23, List of Registers. To
prevent accidental overwriting, TCSR, TCNT, and RSTCSR have to be written to by a different
method to normal registers. For details, refer to section 12.5.1, Notes on Register Access.
Timer counter (TCNT)
Timer control/status register (TCSR)
Reset control/status register (RSTCSR)
12.2.1 Timer Counter (TCNT)
TCNT is an 8-bit readable/writable up-counter. TCNT is initialized to H'00 by a reset, when the
TME bit in TCSR is cleared to 0.
12.2.2 Timer Control/Status Register (TCSR)
TCSR is an 8-bit readable/writable register. Its functions include selecting the clock source to be
input to TCNT, and selecting the timer mode.
Bit Bit Name Initial Value R/W Description
7 OVF 0 R/(W)
*
Overflow Flag
Indicates that TCNT has overflowed. Only a write
of 0 is permitted, to clear the flag.
[Setting condition]
When TCNT overflows (changes from H'FF to
H'00)
When internal reset request generation is
selected in watchdog timer mode, OVF is cleared
automatically by the internal reset.
[Clearing condition]
Cleared by reading TCSR when OVF = 1,
then writing 0 to OVF
When polling CVF when the interval timer
interrupt has been prohibited, OVF = 1 status
should be read two or more times.