; 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 <\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

MOVLW 0DH ; go to second line

CALL _LCD_CHAR

MOVLW 0AH

CALL _LCD_CHAR

MOVF 40H, W ; display location 40H as a char

CALL _LCD_CHAR

MOVLW 0DH ; go to third line

CALL _LCD_CHAR

MOVLW 0AH

CALL _LCD_CHAR

MOVLW 10H ; initialize pointer to RAM location 10

MOVWF FSR

MOVLW .4 ; four values on line

MOVWF _N1

_DEBUG_1:

MOVF INDF, W

CALL _LCD_VAL ; display values in loc 10, 11, 12, 13

INCF FSR, F

MOVLW " "

CALL _LCD_CHAR

DECFSZ _N1, F

GOTO _DEBUG_1

MOVLW 0DH ; go to 4th line

CALL _LCD_CHAR

MOVLW 0AH

CALL _LCD_CHAR

MOVLW .4 ; same for 14, 15, 16 and 17

MOVWF _N1

_DEBUG_2:

MOVF INDF, W

CALL _LCD_VAL

MOVLW " "

CALL _LCD_CHAR

INCF FSR, F

DECFSZ _N1, F

GOTO _DEBUG_2

MOVLW .250

MOVWF _N_MSEC

CALL _DELAY_N ; 250 msecs

CALL _DELAY_N

CALL _DELAY_N

CALL _DELAY_N

GOTO _RETURN

LCD_VAL: ; converts byte in W to two characters and outputs

MOVWF _SAVE_W ; save W and STATUS

SWAPF STATUS, W

MOVWF _SAVE_STAT

SWAPF _SAVE_STAT, F ; save it in true form

MOVF _SAVE_W, W ; get back W

_LCD_VAL:

MOVWF _TEMP1 ; save a copy of W

MOVF PCLATH, W

MOVWF _TEMP2 ; save PCLATH

MOVLW .3 ; page 3

MOVWF PCLATH

SWAPF _TEMP1, W ; high nibble now in lo nibble of W

ANDLW 0FH ;

CALL _HEX_LOOK

CALL _SEROUT

MOVF _TEMP1, W

ANDLW 0FH

CALL _HEX_LOOK

CALL _SEROUT

MOVF _TEMP2, W

MOVWF PCLATH ; previous value of PCLATH

GOTO _RETURN

_HEX_LOOK:

ADDWF PCL, F

DT "0", "1", "2", "3", "4", "5", "6", "7"

DT "8", "9", "A", "B", "C", "D", "E", "F"

LCD_CHAR: ; outputs character in W to LCD

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 back W

_LCD_CHAR:

CALL _SEROUT

MOVLW .10

MOVWF _N_MSEC

CALL _DELAY_N

GOTO _RETURN

_SEROUT: ; transmits content of W at 9600 Baud

MOVWF _SER_DATA

BSF STATUS, RP0 ; make TX bit an output

BCF TRISA, TX ;

BCF STATUS, RP0

BCF PORTA, TX ; set to stop bit

MOVLW .255

MOVWF _SER_TIME ; be sure stop bit has been high present

_SEROUT1: ; for some time

DECFSZ _SER_TIME, F

GOTO _SEROUT1

MOVLW .9

MOVWF _SER_LOOP

BCF STATUS, C ; set C to 0, start bit

_SEROUT2:

BTFSC STATUS, C

BCF PORTA, TX ; send a one

BTFSS STATUS, C

BSF PORTA, TX ; or a zero

MOVLW .31

MOVWF _SER_TIME ; one bit delay. 104 usecs at 9600 baud

_SEROUT3:

DECFSZ _SER_TIME, F

GOTO _SEROUT3

;NOP ; CHANGE

RRF _SER_DATA, F ; least sign bit now in C

DECFSZ _SER_LOOP, F ; does not affect status

GOTO _SEROUT2 ; next character

BCF PORTA, TX ; send stop bit

RETURN

_DELAY_N: ; delays number of msecs specified in _N_MSEC

MOVF _N_MSEC, W

MOVWF _LOOP1

_DELAY_1:

MOVLW .247 ; close to 1.0 msec delay when set to .247

MOVWF _LOOP2

_DELAY_2:

CLRWDT

DECFSZ _LOOP2, F ; decrement and leave result in LOOP2

; skip next statement if zero

GOTO _DELAY_2

DECFSZ _LOOP1, F

GOTO _DELAY_1

RETURN

_RETURN:

SWAPF _SAVE_STAT, W

MOVWF _TEMP2

SWAPF _TEMP2, W

MOVWF STATUS

SWAPF _SAVE_W, W ; get back W without altering STATUS

MOVWF _TEMP2

SWAPF _TEMP2, W

RETURN