NEC PD750004 Manuale Utente

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

Figure 5-23 shows the configuration of the basic interval timer/watchdog timer.

Note Instruction execution

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

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

Vectored 
interrupt 
request 
signal

IRQBT

Wait release 
signal for standby 
release

Set 
signal

BT

8

BTM3

BTM2

BTM1

BTM0

BTM

SET1

3

1

WDTM

Internal
reset signal

SET1