h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 431

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Bit 7—Overflow Flag (OVF): A status flag that indicates that TCNT has overflowed from H'FF
to H'00.
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.
Bit 5—Timer Enable (TME): Selects whether TCNT runs or is halted.
TCSR0 Bit 4—Reset Select (RSTS): Reserved. This bit should not be set to 1.
Bit 7
OVF
0
1
Bit 6
WT/IT IT IT IT
0
1
Bit 5
TME
0
1
* When OVF flag is polled and the interval timer interrupt is disabled, OVF=1 must be
read at least 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: Sends the CPU an interval timer interrupt request (WOVI) when TCNT
overflows
Watchdog timer: Generates a reset or NMI interrupt when TCNT overflows
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 OVFA
Rev. 4.00 Jun 06, 2006 page 377 of 1004
Section 14 Watchdog Timer (WDT)
REJ09B0301-0400
(Initial value)
(Initial value)
(Initial value)