h8s-2169 Renesas Electronics Corporation., h8s-2169 Datasheet - Page 442

• Manufacturer Part Number: h8s-2169
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 14 Watchdog Timer (WDT)
Bit 7—Overflow Flag (OVF): A status flag that indicates that TCNT has overflowed from H'FF
to H'00.
Bit 7
OVF
0
1
Note:
Bit 6—Timer Mode Select (WT/IT IT IT 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 a reset or NMI
interrupt when TCNT overflows. When internal reset is selected in watchdog timer mode, a low-
level signal is output from the RESO pin.
Bit 6
WT/IT IT IT IT
0
1
Bit 5—Timer Enable (TME): Selects whether TCNT runs or is halted.
Bit 5
TME
0
1
Rev. 3.00 Jan 18, 2006 page 414 of 1044
REJ09B0280-0300
* When OVF flag is polled and the interval timer interrupt is disabled, OVF=1 must be
read at last twice.
Description
[Clearing conditions]
[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.)
Description
Interval timer mode: Sends the CPU an interval timer interrupt request (WOVI) when
TCNT overflows
Watchdog timer mode: Generates a reset or NMI interrupt when TCNT overflows
At the same time, a low-level signal is output from the RESO pin (when internal reset
is selected)
Description
TCNT is initialized to H'00 and halted
TCNT counts
Write 0 in the TME bit
Read TCSR when OVF = 1 * , then write 0 in OVF
(Initial value)
(Initial value)
(Initial value)