PIC单片机的LCD例程1

; LCD_F84.ASM
; LCD_RESET - provides a means for the user to manually reset the LCD
; - brings RA.0 (serial lead) low for 2.5 secs. During this
; time, the user should manually reset the LCD.
; - routine then clears the LCD and ouptuts ten dots.
; - LCD is then cleared again.
; - W and STATUS are saved.
; LCD_DEBUG
; - displays W content and the state of the Z and C flags on line 1.
; - prints value of location 40H as a character on line 2.
; - displays values of locations 10, 11, 12, 13 on line 3.
; - locations 14, 15, 16, 17 on line 4.
; - this is followed by a one second delay.
; - the W and STATUS registers are saved and restored in returning
; to the calling program.
;
; LCD_CHAR - displays character in W on LCD. W and STATUS are saved.
; LCD_VAL - converts value in W to two hex characters and displays on LCD.
;
; LCD_BCD_WORD - displays quantity in 41H and 42H as unsigned decimal
; quantity. Note, this is limited to 9999 decimal.
; LIST p=16f84
; #include c:\mplab\p16f84.inc>
; __CONFIG 11h
RADIX HEX
CONSTANT _MAX_VAR=4FH
CONSTANT TX=0 ; PORTA, Bit 0

_SER_DATA EQU _MAX_VAR-0 ; 4F
_SER_LOOP EQU _MAX_VAR-1 ; 4E
_SER_TIME EQU _MAX_VAR-2 ; 4D

_TEMP1 EQU _MAX_VAR-3 ; 4C
_TEMP2 EQU _MAX_VAR-4 ; 4B

_H EQU _MAX_VAR-3 ; 4C
_L EQU _MAX_VAR-4 ; 4B

_TH EQU _MAX_VAR-5 ; 4A
_HU EQU _MAX_VAR-6 ; 49
_TE EQU _MAX_VAR-7 ; 48
_UN EQU _MAX_VAR-8 ; 47

_SAVE_W EQU _MAX_VAR-9 ; 46
_SAVE_STAT EQU _MAX_VAR-0A ; 45

_LOOP1 EQU _MAX_VAR-1 ; used for pace timing, same location as _SER_LOOP
_LOOP2 EQU _MAX_VAR-2 ; used for pace timing, same location as _SER_TIME

_N_MSEC EQU _MAX_VAR-0B ; 44
_N1 EQU _MAX_VAR-0C ; 43

ORG 300H

LCD_BCD_WORD: ; displays a natural binary word in locations 41 and 42
; in decimal.
MOVWF _SAVE_W ; save W and STATUS
SWAPF STATUS, W
MOVWF _SAVE_STAT
SWAPF _SAVE_STAT, F ; status saved in true form

MOVF 41H, W
MOVWF _H
MOVF 42H, W
MOVWF _L

CLRF _TH
CLRF _HU
CLRF _TE
CLRF _UN
_BCD_1:
MOVLW .1
SUBWF _L, F
BTFSC STATUS, C ; a borrow occurred
GOTO _INC_DEC
MOVLW .1
SUBWF _H, F
BTFSC STATUS, C
GOTO _INC_DEC

SWAPF _TH, W
IORWF _HU, W
CALL _LCD_VAL

SWAPF _TE, W
IORWF _UN, W
CALL _LCD_VAL

GOTO _RETURN

_INC_DEC:
CLRWDT
INCF _UN, F
MOVLW .10
SUBWF _UN, W
BTFSS STATUS, Z
GOTO _BCD_1

CLRF _UN

INCF _TE, F
MOVLW .10
SUBWF _TE, W
BTFSS STATUS, Z
GOTO _BCD_1

CLRF _TE

INCF _HU, F
MOVLW .10
SUBWF _HU, W
BTFSS STATUS, Z
GOTO _BCD_1

CLRF _HU

INCF _TH, F
GOTO _BCD_1

LCD_RESET:
MOVWF _SAVE_W ; save W and STATUS
SWAPF STATUS, W
MOVWF _SAVE_STAT
SWAPF _SAVE_STAT, F ; save in true form

BSF STATUS, RP0
BCF TRISA, 0
BCF STATUS, RP0

BCF PORTA, 0 ; output a zero to LCD

MOVLW .10
MOVWF _N1
_RESET_1:
MOVLW .250
MOVWF _N_MSEC
CALL _DELAY_N
DECFSZ _N1, F
GOTO _RESET_1

MOVLW 0CH
CALL _LCD_CHAR

MOVLW .10
MOVWF _N1
_RESET_2:
MOVLW "."
CALL _LCD_CHAR
DECFSZ _N1, F
GOTO _RESET_2

MOVLW .4 ; one second delay
MOVWF _N1

_RESET_3:
MOVLW .250
MOVWF _N_MSEC
CALL _DELAY_N
DECFSZ _N1, F
GOTO _RESET_3

MOVLW 0CH
CALL _LCD_CHAR

GOTO _RETURN

LCD_DELAY: ; delays number of msecs in W
MOVWF _SAVE_W ; save W and STATUS
SWAPF STATUS, W
MOVWF _SAVE_STAT
SWAPF _SAVE_STAT, F ; save in true form

MOVF _SAVE_W, W ; get W
MOVWF _N_MSEC
CALL _DELAY_N

GOTO _RETURN

LCD_DEBUG:
MOVWF _SAVE_W ; save W and STATUS
SWAPF STATUS, W
MOVWF _SAVE_STAT
SWAPF _SAVE_STAT, F

MOVLW 0CH ; clear the LCD
CALL _LCD_CHAR

MOVLW "W" ; W=
CALL _LCD_CHAR
MOVLW "="
CALL _LCD_CHAR
MOVF _SAVE_W, W ; display value of W in hex
CALL _LCD_VAL

MOVLW " "
CALL _LCD_CHAR

MOVLW "Z" ; Z=
CALL _LCD_CHAR
MOVLW "="
CALL _LCD_CHAR

BTFSS _SAVE_STAT, Z
MOVLW "0"
BTFSC _SAVE_STAT, Z
MOVLW "1"

CALL _LCD_CHAR ; display either a zero or one

MOVLW " "
CALL _LCD_CHAR

MOVLW "C" ; C=
CALL _LCD_CHAR
MOVLW "="
CALL _LCD_CHAR

BTFSS _SAVE_STAT, C
MOVLW "0"
BTFSC _SAVE_STAT, C
MOVLW "1"
CALL _LCD_CHAR ; display either a zero or a one