DELAY_HIGH EQU 003H
DELAY_LOW EQU 018H
FLAG_0 EQU 031H
FLAG_1 EQU 032H
FLAG_2 EQU 033H
FLAG_3 EQU 034H
FLAG_4 EQU 035H
FLAG_5 EQU 036H
FLAG_6 EQU 037H
FLAG_7 EQU 038H
FLAG_INVALIDKEY EQU 039H
FLAG_PUSH EQU 040H
NEWKEY EQU 041H
ORG 000H
MOV SP,#050H
LJMP START
ORG 000BH
ACALL INTERRUPT_0
RETI
ORG 001BH
INTERRUPT_1:
PUSH ACC
PUSH PSW
CLR TR1
MOV PSW,#00H
ACALL KEYPRESSED; to check whether any key is pressed or not