NEC PD754144 - Manual (Page 114)

CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
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User’s Manual U10676EJ3V0UM
6.3 Basic Interval Timer/Watchdog Timer
The
µPD754244 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 ( µPD754244 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
µPD754144 (RC oscillation), it is not possible to select the wait time after the release
of standby mode or after a reset. The µPD754144 has almost no oscillation stabilization wait time
and returns to normal operating mode after counting 2 9 /f CC (512 µs at 1.0 MHz).
In the case of
µPD754244 (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.