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CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
114 User’s Manual U10676EJ3V0UM
6.3 Basic Interval Timer/Watchdog Timer
The
µ
PD754244 has an 8-bit basic interval timer/watchdog timer that has the following functions.
(a) Interval timer operation to generate reference time interrupt
(b) Watchdog timer operation to detect program hang-up and reset CPU
(c) To select and count wait time when standby mode is released (
µ
PD754244 only)
(d) To read count value
6.3.1 Configuration of basic interval timer/watchdog timer
Figure 6-20 shows the configuration of the basic interval timer/watchdog timer.
Figure 6-20. Block Diagram of Basic Interval Timer/Watchdog Timer
fx/2
5
fx/2
7
fx/2
9
fx/2
12
MPX
From clock
generator
BTM3 BTM2 BTM1 BTM0
3
4
Basic interval timer
(8-bit divider circuit)
Internal bus
8
BTM
SET1
Note 2
1
WDTM
BT
BT interrupt
request flag
Clear
Wait release signal
when standby
mode is released
Note 1
Clear
Internal
reset signal
SET1
Note 2
Set
Vectored
interrupt
request signal
IRQBT
Notes 1. In the case of the
µ
PD754144 (RC oscillation), it is not possible to select the wait time after the release
of standby mode or after a reset. The
µ
PD754144 has almost no oscillation stabilization wait time
and returns to normal operating mode after counting 2
9
/fCC (512
µ
s at 1.0 MHz).
In the case of
µ
PD754244 (crystal/ceramic oscillation), it is possible to select the wait time after the
release of standby mode.
Refer to CHAPTER 8 STANDBY FUNCTION and CHAPTER 9 RESET FUNCTION, for details.
2. Execution of the instruction.