NEC PD754244 Manuel D’Utilisation

User’s Manual  U10676EJ3V0UM

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

Figure 6-20 shows the configuration of the 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

1

WDTM

BT

BT interrupt
request flag

Clear

Wait release signal
when standby
mode is released

Clear

Internal
reset signal

SET1

Set

Vectored
interrupt
request signal

IRQBT

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.