KiroloesAmir
New Member
I try writing "NO" in the LCD using 4-bit mode. So, I programmed the AT89S52 to send the upper nibble first to the last 4 data inputs of the LCD. I used AND operation to eliminate the lower nibble. Afterwards, I cleared the RS bit and send a HIGH-TO-LOW enable pulse. The same code for the lower nibble but I added Swapping the nibbles of the data byte. The problem is that the LCD writes a strange character, then it clears it. when I press the reset button many times, the string appears in the LCD. I uploaded the following assembly code to the AT89S52:
The crystal value is 24MHz
this is the circuit of the LCD:
a pic of what the LCD writes after it's powered:
View attachment 20210612_223409.jpg
a pic of what the LCD writes when the reset button is pressed many times:
View attachment 20210612_223320.jpg
The crystal value is 24MHz
Code:
ORG 00H
RS BIT P2.7
E BIT P2.6
MOV SP, #25H
MOV P1, #00H
MOV P2, #00H
MOV TMOD, #01H
;;;;;;;;;;;;;;;;;;;;;;;;;;;COMMANDS;;;;;;;;;;;;;;;;;;;;;;;;;;;
MOV R1, #0C8H
ACALL DELAY_MS
MOV R0, #30H ;8-BIT INITIALIZATION
CLR RS ;COMMAND MODE
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
MOV R1, #04H ; 4MS DELAY
ACALL DELAY_MS
MOV R0, #20H ;4-BIT WITH 1 LINE INITIALIZATION
CLR RS ;COMMAND MODE
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
MOV R1, #05H ;50 MICROSECONDS DELAY
ACALL DELAY_US
MOV R0, #28H ;4-BIT MODE OF LCD INITIALIZATION
ACALL CMD
MOV R1, #05H ;50 MICROSECONDS DELAY
ACALL DELAY_US
MOV R0, #0EH ;DISPLAY ON, CURSOR ON
ACALL CMD
MOV R1, #05H ;50 MICROSECONDS DELAY
ACALL DELAY_US
MOV R0, #06H ;ENTRY MODE
ACALL CMD
MOV R1, #05H ;50 MICROSECONDS DELAY
ACALL DELAY_US
MOV R0, #01H ;CLEAR LCD
ACALL CMD
MOV R1, #02H ;2 MS DELAY
ACALL DELAY_MS
MOV R0, #80H ;HOME CURSOR
ACALL CMD
MOV R1, #02H ;2 MS DELAY
ACALL DELAY_MS
MOV R1, #015H ;200 MS DELAY
ACALL DELAY_MS
;;;;;;;;;;;;;;;;;;;;;;;;;;;PRINTING;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
MOV R0, #'N'
ACALL PRNT
MOV R1, #02H
ACALL DELAY_MS
MOV R0, #'O'
ACALL PRNT
MOV R1, #02H
ACALL DELAY_MS
;;;;;;;;;;;;;;;;;;;;;;;;;;;NO LOOPING;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
HERE: SJMP HERE
;;;;;;;;;;;;;;;;;;;;;;;;;;;COMMAND FUNCTION;;;;;;;;;;;;;;;;;;;;;;;;;;
CMD:
;SENDING THE UPPER NIBBLE
MOV A, R0
ANL A, #0F0H
MOV P1, A
CLR RS ;COMMAND MODE
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
;SENDING THE LOWER NIBBLE
MOV A, R0
ANL A, #0FH
SWAP A
MOV P1, A
CLR RS
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;PRINT FUNCTION;;;;;;;;;;;;;;;;;;;;;;;;;;;
PRNT:
;SENDING THE UPPER NIBBLE
MOV A, R0
ANL A, #0F0H
MOV P1, A
SETB RS ;DATA MODE
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
;SENDING THE LOWER NIBBLE
MOV A, R0
ANL A, #0FH
SWAP A
MOV P1, A
SETB RS
SETB E
ACALL DELAY_MS
CLR E
ACALL DELAY_MS
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;DELAY FUNCTION;;;;;;;;;;;;;;;;;;;;;;;;;;
DELAY_MS:
MOV TH0, #0F8H
MOV TL0, #30H
SETB TR0
LOOP: JNB TF0, LOOP
CLR TR0
CLR TF0
DJNZ R1, DELAY_MS
RET
DELAY_US: MOV TH0, #0FFH
MOV TL0, #0ECH
SETB TR0
LOOP1: JNB TF0, LOOP1
CLR TR0
CLR TF0
DJNZ R1, DELAY_US
RET
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
ENDa pic of what the LCD writes after it's powered:
View attachment 20210612_223409.jpg
a pic of what the LCD writes when the reset button is pressed many times:
View attachment 20210612_223320.jpg