UPD78F0838 Renesas Electronics Corporation., UPD78F0838 Datasheet - Page 335

• Manufacturer Part Number: UPD78F0838
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

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8.4 Watch Timer Operations
8.4.1 Watch timer operation
hardware 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.
Remarks 1. f
WTM3
The watch timer generates an interrupt request (INTWT) at a specific time interval by using the peripheral
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.
0
0
1
1
WTM2
2. f
3. f
0
1
0
1
W
PRS
SUB
:
Interrupt Time
2
2
2
2
: Peripheral hardware clock frequency
: Subsystem clock frequency
14
13
5
4
/f
/f
Watch timer clock frequency (f
Selection
/f
/f
W
W
W
W
When Operated at
f
0.5 s
0.25 s
977 s
488 s
SUB
(WTM7 = 1)
= 32.768 kHz
Table 8-4. Watch Timer Interrupt Time
Preliminary User’s Manual U19748EJ1V0UD
CHAPTER 8 WATCH TIMER
When Operated at
1.05 s
0.52 s
2.05 ms
1.02 ms
PRS
f
(WTM7 = 0)
PRS
/2
7
= 2 MHz
or f
SUB
)
When Operated at
0.419 s
0.210 s
819 s
410 s
f
(WTM7 = 0)
PRS
= 5 MHz
When Operated at
0.210 s
0.105 s
410 s
205 s
f
PRS
(WTM7 = 0)
= 10 MHz
0.105 s
52.5 ms
205 s
102 s
at f
When Operated
(WTM7 = 0)
PRS
= 20 MHz
9
333
1/f
W