NEC 78GK0S/K 1+ Series, Application Note

Page: 17 / 37

CHAPTER 4 SETTING METHODS
•
Assembly language program example (same content as in [Example 1] described above and the sample
program)
XMAIN CSEG UNIT
RESET_START:
MOVW AX, #STACKTOP
MOVW SP, AX ;
Set the stack pointer
MOV WDTM, #01101111B ; WDT overflow time = 2^20/fx = 131.07 ms
•
•
•
MOV A, RESF ;
Read the reset source
BF A.4, $CHECK_LVI ;
Go to CHECK_LVI if not a reset by WDT
MOV P2, #00000001B ;
Light LED2
CHECK_LVI:
BT A.0, $SET_CLOCK ;
Omit subsequent LVI-related processing and go to SET_CLOCK
during LVI reset
MOV LVIS, #00000111B ;
Set the low-voltage detection level (VLVI) to 2.85 V +-0.15 V
SET1 LVION ;
Enable the low-voltage detector operation
MOV A, #40 ;
Assign the 200 us wait count value
WAIT_200US:
DEC A
BNZ $WAIT_200US ;
0.5[us/clk]
×
10[clk]
×
40[count] = 200[us]
WAIT_LVI:
MOV WDTE, #0ACH ; Clear the watchdog timer
BT LVIF, $WAIT_LVI ;
Branch if VDD
<
VLVI
SET1 LVIMD ;
Set so that an internal reset signal is generated when VDD
<
VLVI
•
•
•
MAIN_LOOP:
XOR P2, #00000001B ;
Reverse output of LED1
MOV CNT120, #120 ;
Assign the 120 ms wait count value
WAIT_120MS:
CALL !WAIT_1MS ;
Subroutine call for a 1 ms wait
DBNZ CNT120, $WAIT_120MS ;
1[ms]
×
120[count] = 120[ms]
MOV WDTE, #0ACH ; Clear the watchdog timer
BR $MAIN_LOOP ;
Go to the MAIN_LOOP
•
•
•
Setting the WDT overflow time
and operation clock
Clearing WDT before overflow
occurrence and restarting
counting
Clearing WDT before
overflow occurrence and
restarting counting
Remark The above-mentioned wait time (200
μ
s) is calculated with f
CPU
(CPU clock frequency) being 2 MHz, as
done in the sample program.
Application Note U18847EJ1V0AN
17