đây là nguyên đoạn code của nó:
processor 16f877a ; KHAI BAO CHIP
include <p16f877a.inc> ; KHAI BAO HEADER FILE
__CONFIG _CP_OFF&_WDT_OFF&_BODEN_OFF&_PWRTE_ON&_XT_OSC&_WRT _OFF&_LVP_OFF&_CPD_OFF ;KHAI BAO CONFIG
;-----------------------------------------------------------------------
;KHai bao hang
;-----------------------------------------------------------------------
SW1 EQU 0
SW2 EQU 1
SW3 EQU 2
SW4 EQU 3
LED1 EQU 4
LED2 EQU 5
LED3 EQU 6
LED4 EQU 7
;------------------------------------------------------------------------
;Chuong trinh chinh
;------------------------------------------------------------------------
ORG 0x000
GOTO start
start
BCF STATUS, RP1
BCF STATUS, RP0 ;chon bank 0
CLRF PORTB ;xoa PORTB
BSF STATUS, RP0 ;chon bank 1
MOVLW b'00001111'
MOVWF TRISB ;thiet lap pin IO cho PORTB
BCF STATUS, RP0 ;chon bank 0
loop
BTFSS PORTB, SW1 ;kiem tra trang thai SW1
CALL congtac1 ;thuc thi lenh nay neu SW1 duoc nhan
BTFSS PORTB, SW2
CALL congtac2
BTFSS PORTB, SW3
CALL congtac3
BTFSS PORTB, SW4
CALL congtac4
GOTO loop
;---------chuong trinh con congtac-----------
congtac1
CLRF PORTB ;xoa portb
BSF PORTB, LED1 ;bat led1
RETURN ;tro ve chuong trinh chinh
congtac2
CLRF PORTB
BSF PORTB, LED2
RETURN
congtac3
CLRF PORTB
BSF PORTB, LED3
RETURN
congtac4
CLRF PORTB
BSF PORTB, LED4
RETURN
END ;Ket thuc chuong trinh
giờ mình đổi thành thế này:
processor 16f877a ; KHAI BAO CHIP
include <p16f877a.inc> ; KHAI BAO HEADER FILE
__CONFIG _CP_OFF&_WDT_OFF&_BODEN_OFF&_PWRTE_ON&_XT_OSC&_WRT _OFF&_LVP_OFF&_CPD_OFF ;KHAI BAO CONFIG
;-----------------------------------------------------------------------
;KHai bao hang
;-----------------------------------------------------------------------
SW1 SET 0X20
SW2 SET 0X21
SW3 SET 0X22
SW4 SET 0X23
LED1 SET 0X24
LED2 SET 0X25
LED3 SET 0X26
LED4 SET 0X27
;------------------------------------------------------------------------
;Chuong trinh chinh
;------------------------------------------------------------------------
ORG 0x000
GOTO start
start
BCF STATUS, RP1
BCF STATUS, RP0 ;chon bank 0
CLRF PORTB ;xoa PORTB =>PORTB=00000000
BSF STATUS, RP0 ;chon bank 1
MOVLW b'00001111'
MOVWF TRISB ;thiet lap pin IO cho PORTB
BCF STATUS, RP0 ;chon bank 0
loop
BTFSS PORTB, SW1 ;kiem tra trang thai SW1
CALL congtac1 ;thuc thi lenh nay neu SW1 duoc nhan
BTFSS PORTB, SW2
CALL congtac2
BTFSS PORTB, SW3
CALL congtac3
BTFSS PORTB, SW4
CALL congtac4
GOTO loop
;---------chuong trinh con congtac-----------
congtac1
CLRF PORTB ;xoa portb
BSF PORTB, LED1 ;bat led1
RETURN ;tro ve chuong trinh chinh
congtac2
CLRF PORTB
BSF PORTB, LED2
RETURN
congtac3
CLRF PORTB
BSF PORTB, LED3
RETURN
congtac4
CLRF PORTB
BSF PORTB, LED4
RETURN
END ;Ket thuc chuong trinh
kết quả: thay đổi phần khai báo hằng mầ chương trình vẫn chạy như nhau, pó tay