I wrote this code below one year ago on a smaller project for a security sensor system. This time I am face with a similar situation but with an LCD screen to show (*) while the PW is being entered. Also wait until all 5 digits are enterd before determining whether the code is write or wrong. The old code is below:
DISARM: MOV A,P1 ;Entry Code into A.
ANL A,#0FH ;Masking sensors.
CJNE A,#8,ENTRY1 ;Check if first digit is right?
AJMP ENTR12 ;Check sensors again.
DISAM2:
CJNE R4,#4,ENTRY1 ;Check if second digit is right?
AJMP ENTR13 ;Check sensors again.
DISAM3:
CJNE R0,#0,ENTRY1 ;Check if 3rd digit is right?
AJMP DIAMF ;Congratulations.
;********************************************
;****************HERE COMES THE THE MAGICIAN****************************
;*********DISPLAYING ZONES (without system being ARMED******************
DISP1: SETB P3.2 ;Display 4.
CJNE A,#0E0H,N_Z1 ;If another ZONE is trigger,
;clear this ZONE on the display.
SJMP DISP1 ;Otherwise, continue to display 4.
N_Z1: CLR P3.2 ;Clear 4 on display.
LJMP JONE1 ;Back to monitoring home.
DISP2: MOV 0B0H,#03 ;Display 3.
CJNE A,#0D0H,N_Z2 ;If another ZONE is trigger,
;clear this ZONE on the display.
SJMP DISP2 ;Otherwise, continue to display 3.
N_Z2: MOV 0B0H,#00H ;Clear display. (clear port 3).
LJMP ZONE1 ;Back to monitoring home.
DISP3: SETB P3.1 ;Display 2.
CJNE A,#0BH,N_Z3 ;If another ZONE is trigger,
;clear this ZONE on the display.
SJMP DISP3 ;Otherwise, continue to display 2.
N_Z3: CLR P3.1 ;clear 2 on dispaly.
LJMP ZONE1 ;Back to monitoring home.
DISP4: SETB P3.0 ;Display 1.
CJNE A,#70H,N_Z4 ;If another ZONE is trigger,
;clear this ZONE on the display.
SJMP DISP4 ;Otherwise, continue to display 1.
N_Z4: CLR P3.0 ;Clear display.
LJMP ZONE1 ;Back to monitoring zones.
;********************************************
;****************CHECKING FOR CORRECT CODE*******************************

ENTR12: MOV A,P1 ;check for correct 2nd code.
ANL A,#0FH ;Masking off sensors.
CJNE A,#4,ENTRY1 ;Check Zone 1 else, Zone 2.
MOV R4,A ;content of A in R4
LJMP DISAM2 ;continue check of correct code.
ENTR13: MOV A,P1 ;checking for correct 3rd code.
ANL A,#0FH ;Masking off sensors.
CJNE A,#00,ENTRY1 ;Check Zone 2 else, Zone 3.
MOV R0,A ;A contents in R0.
LJMP DISAM3 ;Check for correct final code.
The last time I was using an 8051 and now I am using a ROMless 80c31 with an external EEPROM also 20 by 4 line LCD. Please help with the code.