NEC PD750008 Manuale Utente
99
CHAPTER 5 PERIPHERAL HARDWARE FUNCTIONS
5.3 BASIC INTERVAL TIMER/WATCHDOG TIMER
The µPD750008 contains an 8-bit basic interval timer/watchdog timer, which has the following functions:
(a) Interval timer operation which generates a reference timer interrupt
(b) Operation as a watchdog timer for detecting program crashes and resetting the CPU
(c) Selection of a wait time for releasing the standby mode, and counting
(d) Reading the count value
5.3.1 Configuration of the Basic Interval Timer/Watchdog Timer
Figure 5-23 shows the configuration of the basic interval timer/watchdog timer.
Figure 5-23. Block Diagram of the Basic Interval Timer/Watchdog Timer
Note Instruction execution
5.3.2 Basic Interval Timer Mode Register (BTM)
The BTM is a 4-bit register for controlling operation of the basic interval timer (BT).
A 4-bit memory manipulation instruction is used to set the BTM.
Bit 3 can be independently manipulated using a bit manipulation instruction.
Example The interrupt generation interval is set to 1.37 ms (at 6.00 MHz).
SEL
MB15
; or CLR1 MBE
MOV
A,#1111B
MOV
BTM,A
; BTM <– 1111B
From the clock
generator
generator
Internal bus
4
f
X
/2
5
f
X
/2
7
f
X
/2
9
f
X
/2
12
MPX
Basic interval timer
(8-bit frequency divider)
Clear signal
Clear signal
BT interrupt
request flag
request flag
Vectored
interrupt
request
signal
interrupt
request
signal
IRQBT
Wait release
signal for standby
release
signal for standby
release
Set
signal
signal
BT
8
BTM3
BTM2
BTM1
BTM0
BTM
SET1
Note
3
1
WDTM
Internal
reset signal
reset signal
SET1
Note