; initialise the display
; see instruction set for details


	CLR P1.3		; clear RS - indicates that instructions are being sent to the module

; function set	
	CLR P1.7		; |
	CLR P1.6		; |
	SETB P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear	
				; function set sent for first time - tells module to go into 4-bit mode
; Why is function set high nibble sent twice? See 4-bit operation on pages 39 and 42 of HD44780.pdf.

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E
				; same function set high nibble sent a second time

	SETB P1.7		; low nibble set (only P1.7 needed to be changed)

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E
				; function set low nibble sent

	CALL delay		; wait for BF to clear


; entry mode set
; set to increment with no shift
	CLR P1.7		; |
	CLR P1.6		; |
	CLR P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	SETB P1.6		; |
	SETB P1.5		; |low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; display on/off control
; the display is turned on, the cursor is turned on and blinking is turned off
	CLR P1.7		; |
	CLR P1.6		; |
	CLR P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	SETB P1.7		; |
	SETB P1.6		; |
	SETB P1.5		; | low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; put Euro symbol in RAM
	MOV 30H, #110B		;   **
	MOV 31H, #1001B		;  *  *
	MOV 32H, #11110B	; ****
	MOV 33H, #1000B		;  *
	MOV 34H, #11110B	; ****
	MOV 35H, #1001B		;  *  *
	MOV 36H, #110B		;   **
	MOV 37H, #0		; | end of data (in this example, 0 can be used to indicate end of data because 
				; | none of the rows themselves contain 0)


; set CGRAM address
; set to character 4, row 0 (address 100 000B = 20H)
	CLR P1.7		; |
	SETB P1.6		; |
	SETB P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CLR P1.6		; |
	CLR P1.5		; |low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; send euro symbol to CGRAM
	SETB P1.3		; set RS - indicates that data is being sent to module
	MOV R1, #30H		; point to first row, stored in 8051 RAM location 30H
loop:
	MOV A, @R1		; move row being pointed to by R1 to A
	JZ endEuroEntry		; if A is 0, then end of data has been reached - jump out of loop
	CALL sendCharacter	; send current row to LCD module
	INC R1			; point to next row
	JMP loop		; repeat

endEuroEntry:


; set DDRAM address
; set to 0
	CLR P1.3		; clear RS - indicates that instructions are being sent to the module

	SETB P1.7		; |
	CLR P1.6		; |
	CLR P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CLR P1.7		; |low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; display Euro symbol (by sending 4 to DDRAM)
	SETB P1.3		; set RS - indicates that data is being sent to module
	MOV A, #4		; | now that A contains 4, data in CGRAM
	CALL sendCharacter	; | location 4 will be displayed (ie: euro symbol)



	JMP $			; end of program - do nothing



; sendCharacter subroutine

sendCharacter:
	MOV C, ACC.7		; |
	MOV P1.7, C		; |
	MOV C, ACC.6		; |
	MOV P1.6, C		; |
	MOV C, ACC.5		; |
	MOV P1.5, C		; |
	MOV C, ACC.4		; |
	MOV P1.4, C		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	MOV C, ACC.3		; |
	MOV P1.7, C		; |
	MOV C, ACC.2		; |
	MOV P1.6, C		; |
	MOV C, ACC.1		; |
	MOV P1.5, C		; |
	MOV C, ACC.0		; |
	MOV P1.4, C		; | low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear

delay:
	MOV R0, #50
	DJNZ R0, $
	RET