NEC PD754144 - Manual (Page 120)

CHAPTER 6 PERIPHERAL HARDWARE FUNCTION
120
User’s Manual U10676EJ3V0UM
Example To use the µPD754244 as a watchdog timer with a time interval of 5.46 ms (at f
X
= 6.0 MHz). Note
Divide the program into several modules, each of which is completed within the set time of BTM (5.46
ms), and clear BT at the end of each module. If a hang-up occurs, BT is not cleared within the set
time. As a result, BT overflows, and the internal reset signal is asserted.
Initial setting:
SET1
SEL
MOV
MOV
SET1
.
.
.
MBE
MB15
A, #1101B
BTM, A
WDTM
; Sets time and starts
; Enables watchdog timer
(After that, set bit 3 of BTM to “1” every 5.46 ms.)
Module 1:
.
.
.
.
.
.
SET1
SEL
SET1
MBE
MB15
BTM.3
Processing completed
within 5.46 ms
Module 2:
.
.
.
.
.
.
SET1
SEL
SET1
MBE
MB15
BTM.3
Processing completed
within 5.46 ms
.
.
.
Note It is 7.81 ms when the µPD754244 is operating at f
X
= 4.19 MHz.
In the case of the µPD754144, it is 32.8 ms at f
CC = 1.0 MHz.