upd78f0114hgb-8es-a Renesas Electronics Corporation., upd78f0114hgb-8es-a Datasheet - Page 209

• Manufacturer Part Number: upd78f0114hgb-8es-a
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

9.4 Watch Timer Operations
9.4.1 Watch timer operation
clock or subsystem clock.
operation starts. When these bits are cleared to 0, the 5-bit counter is cleared and the count operation stops.
clearing WTM1 to 0. In this case, however, the 11-bit prescaler is not cleared. Therefore, an error up to 2
seconds occurs in the first overflow (INTWT) after zero-second start.
Remark
The watch timer generates an interrupt request (INTWT) at a specific time interval by using the high-speed system
When bit 0 (WTM0) and bit 1 (WTM1) of the watch timer operation mode register (WTM) are set to 1, the count
When the interval timer is simultaneously operated, zero-second start can be achieved only for the watch timer by
The interrupt request is generated at the following time intervals.
WTM3
0
0
1
1
f
f
f
X
XT
W
: High-speed system clock oscillation frequency
: Watch timer clock frequency
: Subsystem clock oscillation frequency
WTM2
0
1
0
1
2
2
2
2
Interrupt Time Selection
14
13
5
4
/f
/f
/f
/f
W
W
W
W
Table 9-4. Watch Timer Interrupt Time
CHAPTER 9 WATCH TIMER
User’s Manual U16961EJ4V0UD
0.5 s
0.25 s
977 s
488 s
When Operated at f
(WTM7 = 1)
XT
= 32.768 kHz
0.210 s
0.105 s
410 s
205 s
When Operated at f
(WTM7 = 0)
X
= 10 MHz
9
209
1/f
W