Basic Interval Timer/Watchdog Timer; Configuration Of The Basic Interval Timer/Watchdog Timer; Basic Interval Timer Mode Register (Btm); Block Diagram Of The Basic Interval Timer/Watchdog Timer - NEC PD750004 User Manual

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
From the clock
generator
5
f /2
X
7
f /2
X
9
f /2
X
12
f /2
X
BTM3 BTM2
Note
4
SET1
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
MOV
MOV
MPX
(8-bit frequency divider)
3
BTM1 BTM0 BTM
Internal bus
MB15 ; or CLR1 MBE
A,#1111B
BTM,A ; BTM <– 1111B
CHAPTER 5 PERIPHERAL HARDWARE FUNCTIONS
Clear signal
Basic interval timer
BT
Wait release
signal for standby
release
8
Set
signal
BT interrupt
request flag
IRQBT
Note
SET1
WDTM
1
Clear signal
Vectored
interrupt
request
signal
Internal
reset signal
99