;*************************************************************************
;
; lcd_gld subroutine: modified lcddrv3.a51 from EMAC (see notes below)
; 
;*************************************************************************

$NOMOD51		; omit assembler micro definitions
$Include(reg515.inc)	; define 515 micro

Name	LCD_GLD
PUBLIC	lcdout, lcdinit, DLAYZ, DLAYA, DLAYB, DLAYC

LCD_DRV		SEGMENT	CODE
RSEG		LCD_DRV			; switch to this code segment
USING		0				; use register_bank 0 



;************************************************************************
;
; 20X2 character LCD drivers for the MICROPAC 535
;
; COPYRIGHT 1993-1995 EMAC INC.
;
; ESCflag is a bit field that must be declared.
; DLAYA is a 5ms delay routine with no registers affected.
; LCDINIT should be executed before any other LCD subroutines.
;
;        
; LCDOUT: Output the char in ACC to LCD        
; Following are some codes that are supported by this driver (20*2 displays)
;
;        0ah      move cursor to other line (i.e. from 1-2 or 2-1)
;        0dh      move cursor to beginning of line 
;        1ah      clear display and move cursor to home
;        1bh      the next byte received after this will be written to register
;                 0 of the lcd display
;                  

; definitions

escflag		equ	psw.5		; LCD equate
lcdcmd   	equ      28h      	; value for P2 to select lcd command port
initdata:
         db       38h,08,01,06,0eh,80h,0
;--------------------------------------------------------------
; Dempsey notes
; (1) R1,R2 are corrupted by this subroutine
; (2) Previously there were several returns- now only one: "LCDEXIT"
; (3) From calling program: Use a delay of 5ms (minimum)
;     between command codes LF (0A) and CR (0D)
;---------------------------------------------------------------  

LCDOUT:  
	MOV	R2,A              ; SAVE CHAR IN R2
	MOV	P2,#LCDCMD        ; POINT TO COMMAND PORT
	jnb	ESCflag,lcdnt5    ; skip if no ESC
	clr	escflag
	sjmp	reg0out           ; write directly to lcd reg 0

lcdnt5:
	ANL	A,#11100000B      ; SEE IF ANY OF UPPER 3 BITS SET
	JNZ	REG1OUT           ; IF YES, PRINT IT
	MOV	A,R2              ; RESTORE CHAR
	ANL	A,#11111000B      ; SEE IF CHAR IS < 7
	JZ	REG1OUT           ; IF LESS, A=0 SO PRINT USER DEF CHAR 0-7
         
	MOV	A,R2              ; SEE IF CONTROL CHAR
	CJNE	A,#0DH,LCNT1      ; IF NOT CR, SKIP
	MOVX	A,@R1             ; READ COMMAND PORT TO FIND CURSOR POS
	SETB	ACC.7             ; SET BIT 7 FOR DDRAM ADDR
	ANL	A,#11100000B      ; MOVE TO LEFT (ONLY VALID ON 2 LINE DISPL)
	MOV	R2,A
	SJMP	REG0OUT
         
LCNT1:	CJNE	A,#0AH,LCNT2      ; IF NOT LF, SKIP
	MOVX	A,@R1             ; READ COMMAND PORT TO FIND CURSOR POS
	CPL	ACC.6             ; SWITCH LINE (ONLY VALID ON 2 LINE DISPL)
	SETB	ACC.7             ; SET BIT 7 FOR DDRAM ADDR
	MOV	R2,A
	SJMP	REG0OUT
         
LCNT2: 	CJNE	A,#1BH,LCNT3      ; IF NOT ESC, SKIP
	setb	ESCflag           ; indicate ESC received
	JMP LCDEXIT
         
LCNT3: 	CJNE	A,#1AH,LCNT4	  ; EXIT IF NOT CLEAR SCREEN
	MOV	R2,#1             ; CLEAR COMMAND
	SJMP	REG0OUT

				  ; OUTPUT THE CHAR IN R2 TO REG 1
REG1OUT:
	MOVX	A,@R1             ; READ LCD COMMAND PORT
	JB 	ACC.7,REG1OUT     ; LOOP IF BUSY FLAG SET
	INC	P2                ; POINT TO LCD DATA PORT         
	MOV	A,R2              ; RESTORE CHAR
	MOVX	@R1,A             ; OUTPUT IT
LCNT4:	JMP LCDEXIT

         
        			  ; OUTPUT THE CHAR IN R2 TO REG 0
REG0OUT:
	MOVX	A,@R1             ; READ LCD COMMAND PORT
	JB  	ACC.7,REG0OUT     ; LOOP IF BUSY FLAG SET
	MOV	A,R2              ; RESTORE CHAR
	MOVX	@R1,A             ; OUTPUT IT
     	JMP LCDEXIT
        
; 
; LCDINIT: Init the LCD
;         
LCDINIT:         
	clr 	ESCflag           ; indicate no esc found
	MOV  	P2,#LCDCMD        ; POINT TO COMMAND PORT
	LCALL  	DLAYA             ; 5MS DELAY
	LCALL  	DLAYA             ; 5MS DELAY
	LCALL  	DLAYA             ; 5MS DELAY
	LCALL 	DLAYA             ; 5MS DELAY
	MOV    	A,#30H
	MOVX  	@R1,A             ; OUT TO LCD COMMAND PORT         
	LCALL 	DLAYA             ; 5MS DELAY         
	MOVX  	@R1,A             ; OUT TO LCD COMMAND PORT                  
	LCALL 	DLAYA             ; 5MS DELAY         
	MOVX  	@R1,A             ; OUT TO LCD COMMAND PORT                  
         
	MOV  	DPTR,#INITDATA    ; POINT TO INIT DATA
        		          ; the last command should take no more than 40 uS. 
  	mov	b,#80             ; for timeout of 80*3 * (12/clock)
lcdnit2:
	movx 	a,@r1             ; read lcd command port
     	jnb   	acc.7,lcdnit1     ; exit if not busy
     	djnz 	b,lcdnit2         ; loop till timeout
     	sjmp 	lcdexit	; exit if timeout

LCDNIT1:
	MOVX 	A,@R1             ; READ LCD COMMAND PORT
      	JB   	ACC.7,LCDNIT1     ; LOOP IF BUSY FLAG SET				      
     	CLR  	A
     	MOVC  	A,@A+DPTR         ; GET BYTE FROM INIT TABLE
     	JZ    	LCDEXIT           ; EXIT IF 0
    	INC   	DPTR              ; POINT TO NEXT BYTE        
     	MOVX  	@R1,A             ; OUTPUT BYTE
    	SJMP   	LCDNIT1           ; LOOP
         
LCDEXIT:
	RET   




;
; MISCELLANEOUS DELAYS
;
DLAYZ:	PUSH 	ACC
      	MOV    	A,#5
      	AJMP  	DLAYA2
      	
DLAYA:	PUSH 	ACC
      	MOV    	A,#100
      	AJMP  	DLAYA2

DLAYB: 	PUSH   	ACC
      	MOV   	A,#128
       	AJMP  	DLAYA2

DLAYC: 	PUSH 	ACC
      	MOV   	A,#255
       	AJMP  	DLAYA2
dlayd: 	push 	acc
      	mov 	a,#8


DLAYA2:
     	PUSH 	ACC
     	MOV   	A,#0FFH
DLAYA1: 
       	MOV   	A,#0FFH
     	DJNZ  	ACC,$             ; LEVEL 3 LOOP            
     	POP   	ACC
     	DJNZ  	ACC,DLAYA2        ; LEVEL 1 LOOP
         
     	POP   	ACC
	RET

	
	END