Datasheet

Section 14 Watchdog Timer (WDT)
R01UH0309EJ0500 Rev. 5.00 Page 849 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
14.3 Register Descriptions
The WDT has the following three registers. To prevent accidental overwriting, TCSR, TCNT, and
RSTCSR have to be written to in a method different from normal registers. For details, refer to
section 14.6.1, Notes on Register Access.
• Timer counter (TCNT)
• Timer control/status register (TCSR)
• Reset control/status register (RSTCSR)
14.3.1 Timer Counter (TCNT)
TCNT is an 8-bit readable/writable up-counter. TCNT is initialized to H'00 when the TME bit in
TCSR is cleared to 0.
14.3.2 Timer Control/Status Register (TCSR)
TCSR selects the clock source to be input to TCNT, and the timer mode.
Bit Bit Name Initial Value R/W Description
7 OVF 0 R/(W)
*
Overflow Flag
Indicates that TCNT has overflowed in interval
timer mode. Only a write of 0 is permitted, to clear
the flag.
[Setting condition]
When TCNT overflows in interval timer mode
(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 conditions]
Cleared by reading TCSR when OVF = 1, then
writing 0 to OVF