Файл: Microcontroller Programming. Thi Micro Chip PIC (Julio Sanchez, 2007).pdf

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528		Chapter 15
; Display character on LCD
call	send8	; Display in LCD
call	LCDscroll	; Scroll at end of line
incf	EEMemAdd,f	; Next EEPROM byte
goto	readOne
; End of execution
atEnd:
goto	atEnd

;============================================================

;============================================================ ; L O C A L P R O C E D U R E S ;============================================================ ;============================================================ ;==========================

;init LCD for 4-bit mode ;========================== initLCD:

;Initialization for Densitron LCD module as follows:

;4-bit interface

;2 display lines of 16 characters each

;cursor on

;left-to-right increment

;cursor shift right

;no display shift

;=======================|

;	set command mode		\|
;=======================\|
	bcf	PORTE,E_line
	bcf	PORTE,RS_line
	bcf	PORTE,RW_line
	call	delay_125
	movlw	0x28
SET)

;E line low

;RS line low

;Write mode

;delay 125 microseconds

;0 0 1 0 1 0 0 0 (FUNCTION

call	send8				; 4-bit send routine
; Set 4-bit mode command must be repeated
movlw	0x28
call	send8
movlw	0x0e	; 0	0	0	0	1	1	1	0 (DISPLAY ON/OFF)
call	send8
movlw	0x06	; 0	0	0	0	0	1	1	0 (ENTRY MODE SET)
call	send8
movlw	0x14	; 0	0	0	1	0	1	0	0 (CURSOR/DISPLAY
SHIFT)
call	send8
movlw	0x01	; 0	0	0	0	0	0	0	1 (CLEAR DISPLAY)
call	send8
call	delay_5	; Test for busy

Data EEPROM Programming			529
	return
.;===========================
;	procedure to clear LCD
;============================
clearLCD:
	bcf	PORTE,E_line	; E line low
	bcf	PORTE,RS_line	; RS line low
	bcf	PORTE,RW_line	; Write mode
	call	delay_125	; delay 125 microseconds
	movlw	0x01	; 0 0 0 0 0 0 0 1
	call	send8
	call	delay_5 ; Test for busy
	return

;=======================

;Procedure to delay

;42 microseconds ;======================= delay_125:

movlw	.105	; Repeat 105 machine cycles
movwf	count1	; Store value in counter
repeat:
decfsz	count1,f	; Decrement counter
goto	repeat	; Continue if not 0
return		; End of delay

;=======================

;Procedure to delay

;5 milliseconds ;======================= delay_5:

	movlw	.105	; Counter = 105 cycles
	movwf	count2	; Store in variable
delay:
	call	delay_125	; Delay
	decfsz	count2,f	; 40 times = 5 milliseconds
	goto	delay
	return		; End of delay
;========================
;	pulse E line
;========================
pulseE
	bsf	PORTE,E_line	; Pulse E line
	nop
	bcf	PORTE,E_line
	return

530			Chapter 15
;=============================
;	long delay sub-routine
;=============================
long_delay:
	movlw	D’200’	; w delay count
	movwf	J	; J = w
jloop:
	movwf	K	; K = w
kloop:
	decfsz	K,f	; K = K-1, skip next if zero
	goto	kloop
	decfsz	J,f	; J = J-1, skip next if zero
	goto	jloop
	return

;========================

;send 2 nibbles in

;4-bit mode ;========================

;Procedure to send two 4-bit values to Port-B lines

;7, 6, 5, and 4. High-order nibble is sent first

;ON ENTRY:

;w register holds 8-bit value to send

send8:

movwf	store1	; Save original value
call	merge4	; Merge with Port-B
; Now w has merged byte
movwf	PORTD	; w to Port-D
call	pulseE	; Send data to LCD
; High nibble is sent
movf	store1,w ; Recover byte into w
swapf	store1,w ; Swap nibbles in w
call	merge4
movwf	PORTD
call	pulseE	; Send data to LCD
call	delay_125
return

;==========================

;merge bits ;==========================

;Routine to merge the 4 high-order bits of the

;value to send with the contents of Port-B

;so as to preserve the 4 low-bits in Port-B

;Logic:

;AND value with 1111 0000 mask

;AND Port-B with 0000 1111 mask

;Now low nibble in value and high nibble in

;Port-B are all 0 bits:

;value = vvvv 0000

Data EEPROM Programming

531

;Port-B = 0000 bbbb

;OR value and Port-B resulting in:

;

vvvv bbbb

;ON ENTRY:

;w contain value bits

;ON EXIT:

;w contains merged bits

merge4:

andlw	b’11110000’	; ANDing with	0 clears the
		; bit. ANDing	with 1 preserves
		; the original value
movwf	store2	; Save result	in variable
movf	PORTD,w	; Port-B to w	register
andlw	b’00001111’	; Clear high nibble in Port-b
		; and preserve low nibble
iorwf	store2,w ; OR two operands in w
return

;==========================

;Set address register

;to LCD line 2 ;==========================

;ON ENTRY:

;Address of LCD line 2 in constant LCD_2

line2:

bcf	PORTE,E_line	; E line low
bcf	PORTE,RS_line	; RS line low, setup for
control
call	delay_5	; Busy?
; Set to second display line
movlw	LCD_2	; Address with high-bit set
call	send8
; Set RS line for data
bsf	PORTE,RS_line	; RS = 1 for data
call	delay_5	; Busy?
return

;==========================

;Set address register

;to LCD line 1 ;==========================

;ON ENTRY:

;Address of LCD line 1 in constant LCD_1

line1:

bcf	PORTE,E_line	; E line low
bcf	PORTE,RS_line	; RS line low, set up for
control
call	delay_5	; busy?
; Set to second display line
movlw	LCD_1	; Address and command bit

532		Chapter 15
call	send8	; 4-bit routine
; Set RS line for data
bsf	PORTE,RS_line	; Setup for data
call	delay_5	; Busy?
return

;==========================

;scroll to LCD line 2 ;==========================

;Procedure to count the number of characters displayed on

;each LCD line. If the number reaches the value in the

;constant LCDlimit, then display is scrolled to the second

;LCD line. If at the end of the second line, then LCD is

;reset to the first line.

LCDscroll:
incf	LCDcount,f	; Bump counter
; Test for line limit
movf	LCDcount,w
sublw	LCDlimit	; Count minus limit
btfss	STATUS,Z	; Is count - limit = 0
goto	scrollExit	; Go if not at end of line

;At this point the end of the LCD line was reached

;Test if this is also the end of the second line movf LCDline,w

sublw	0x01	; Is it line 1?
btfsc	STATUS,Z	; Is LCDline minus 1 = 0?
goto	line2End	; Go if end of second line
; At this point it is the end of the top LCD line
call	line2	; Scroll to second line
clrf	LCDcount	; Reset counter
incf	LCDline,f	; Bump line counter
goto	scrollExit
; End of second LCD line
line2End:
call	initLCD	; Reset
clrf	LCDcount	; Clear counters
clrf	LCDline
call	line1	; Display to first line
scrollExit:
return