NEC PD754244 Manuel D’Utilisation

User’s Manual  U10676EJ3V0UM

When WDTM is reset to “0”, the interrupt request flag (IRQBT) is set by the overflow of the basic interval timer

(BT), and the basic interval timer/watchdog timer operates as the basic interval timer.  BT is always incremented by

the clock supplied by the clock generator and its counting operation cannot be stopped.

Four time intervals at which an interrupt occurs can be selected by BTM (

µPD754244 only.  Refer to Figure 6-

21).

By setting bit 3 of BTM to “1”, BT and IRQBT can be cleared (command to start the interval timer).

The count value of BT can be read by using an 8-bit manipulation instruction.  No data can be written to BT.

Start the timer operation as follows (<1> and <2> may be performed simultaneously).

<1>  Set interval time to BTM.

<2>  Set bit 3 of BTM to “1”.

To generate an interrupt at intervals of the 

µPD754244 of 1.37 ms (at f

X

 = 6.0 MHz)

SET1

MBE

SEL

MB15

MOV

A, #1111B

MOV

BTM, A

; Sets time and starts

EI

; Enables interrupt

EI

IEBT

; Enables BT interrupt

Note It is 1.95 ms when the 

µPD754244 is operating at f

X

 = 4.19 MHz.

In the case of the 

µPD754144, it is 8.19 ms at f

CC

 = 1.0 MHz.