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

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Supplementary Programs

763

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

;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

;port B = 0000 bbbb

;OR value and port B resulting in:

;

vvvv bbbb

;ON ENTRY:

;w contains 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

764	Appendix D

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

;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
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:

Supplementary Programs		765
call	initLCD	; Reset
clrf	LCDcount	; Clear counters
clrf	LCDline
call	line1	; Display to first line
scrollExit:
return

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

;first text string procedure ;=============================== storeMS1:

;Procedure to store in PIC RAM buffer the message

;contained in the code area labeled msg1

;ON ENTRY:

;variable pic_ad holds address of text buffer

;in PIC RAM

;w register hold offset into storage area

;msg1 is routine that returns the string characters

;and a zero terminator

;index is local variable that hold offset into

;text table. This variable is also used for

;temporary storage of offset into buffer

;ON EXIT:

;Text message stored in buffer

;

;Store offset into text buffer (passed in the w register)

;in temporary variable

movwf	index	; Store w in index
; Store base address of text buffer in FSR
movf	pic_ad,w ; first display RAM address to W
addwf	index,w	; Add offset to address
movwf	FSR	; W to FSR
; Initialize index for text string access
movlw	0	; Start at 0
movwf	index	; Store index in variable
; w still = 0
get_msg_char:
call	msg1	; Get character from table
; Test for zero terminator
andlw	0x0ff
btfsc	STATUS,Z	; Test zero flag
goto	endstr1	; End of string

;ASSERT: valid string character in w

;store character in text buffer (by FSR)

movwf	INDF	; store in buffer by FSR
incf	FSR,f	;	increment	buffer pointer
; Restore table character counter from variable
movf	index,w	;	Get value	into w

766		Appendix D
addlw	1	; Bump to next character
movwf	index	; Store table index in
variable
goto	get_msg_char	; Continue
endstr1:
return

;Routine for returning message stored in program area

;Message has 10 characters

msg1:

addwf	PCL,f	; Access table
retlw	'I'
retlw	't'
retlw	'e'
retlw	'r'
retlw	'.'
retlw	0x20
retlw	'N'
retlw	'o'
retlw	'.'
retlw	0x20
retlw	0

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

;blank buffer ;========================

;Procedure to store 20 blank characters in PIC RAM

;buffer starting at address stored in the variable

;pic_ad

blank20:
movlw	D'20'	; Setup counter
movwf	count1
movf	pic_ad,w ; First PIC RAM address
movwf	FSR	; Indexed addressing
movlw	0x20	; ASCII space character
storeit
movwf	INDF	; Store blank character in PIC RAM
		; buffer using FSR register
decfsz	count1,f	; Done?
goto	incfsr	; no
return		; yes
incfsr
incf	FSR,f	; Bump FSR to next buffer space
goto	storeit

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

;binary to ASCII decimal

;conversion ;==============================

;ON ENTRY:

Supplementary Programs

767

;w register has binary value in range 0 to 255

;ON EXIT:

;output variables asc100, asc10, and asc1 have

;three ASCII decimal digits

;Routine logic:

;The value 100 is subtracted from the source operand

;until the remainder is < 0 (carry cleared). The number

;of subtractions is the decimal hundreds result. 100 is

;then added back to the subtrahend to compensate

;for the last subtraction. Now 10 is subracted in the

;same manner to determine the decimal tenths result.

;The final remainder is the decimal units result.

;Variables:

;

inNum

storage for source operand

;asc100 storage for hundreds position result

;	asc10	storage for tenth position result
;	asc1	storage for unit position reslt
;	thisDig	Digit counter
bin2asc:
	movwf	inNum	; Save copy of source value
	clrf	asc100	; Clear hundreds storage
	clrf	asc10	; Tens
	clrf	asc1	; Units
	clrf	thisDig
sub100:
	movlw	.100
	subwf	inNum,f		; Subtract 100
	btfsc	STATUS,C		; Did subtract overflow?
	goto	bump100		; No. Count subtraction
	goto	end100
bump100:
	incf	thisDig,f		;increment digit counter
	goto	sub100
; Store 100th digit
end100:
	movf	thisDig,w		; Adjusted digit counter
	addlw	0x30		; Convert to ASCII
	movwf	asc100		; Store it
; Calculate tenth position value
	clrf	thisDig
; Adjust minuend
	movlw	.100		; Minuend
	addwf	inNum,f		; Add value to minuend to
				; compensate for last
				; operation
sub10:
	movlw	.10
	subwf	inNum,f		; Subtract 10

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

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