2019年10月21日 | 以汇编语言写的PIC18Fxxxx的LCD驱动程序

;************************************************

;* 18F_LCD.asm *

;* Microchip Taiwan                             *

;* Date : Sept. 24 2002 *

;* Version : v1.00 *

;************************************************

;* Contains subroutines to control an external  *

;* lcd panel in 4-bit mode.  These routines     *

;* were designed specifically for the panel on  *

;* the PICdemo 2 Plus demo board, but should    *

;* work with other LCDs with a HD44780 type     *

;* controller.                                  *

;* Routines include:                            *

;*   - InitLCD to initialize the LCD panel      *

;*   - putcLCD to write a character to LCD      *

;*   - SendCmd to write a command to LCD        *

;*   - clrLCD to clear the LCD display          *

;*   - L1homeLCD to return cursor to line 1 home*

;*   - L2homeLCD to return cursor to line 2 home*

;*   - PutHexLCD to write a HEX Code to LCD     *

;*   - Hex2ASCII to convert 4 bits to ASCII Code*

;************************************************

;

list p=18F452

#include

;

global InitLCD

global putcLCD

global clrLCD

global L1homeLCD

global L2homeLCD

global  Send_Cmd

global PutHexLCD

global Hex2ASCII

global Delay_xMS

global Delay_1mS

;

; Defines for I/O ports that provide LCD data & control

; PORTD[0:3]-->DB[4:7]: Higher order 4 lines data bus with bidirectional

;   : DB7 can be used as a BUSY flag

; PORTA,1 --> [E] : LCD operation start signal control 

; PORTA,2 --> [RW]: LCD Read/Write control

; PORTA,3 --> [RS]: LCD Register Select control

;   : "0" for Instrunction register (Write), Busy Flag (Read)

;   : "1" for data register (Read/Write)

;

;

LCD_CTRL equ TRISD

LCD_DATA equ PORTD

#define LCD_E_DIR TRISA,1

#define LCD_RW_DIR TRISA,2

#define LCD_RS_DIR TRISA,3

#define LCD_E PORTA,1

#define LCD_RW PORTA,2

#define LCD_RS PORTA,3  

; LCD Module commands

CLR_DISP equ b'00000001' ; 1.64mS , Clear display and return cursor to home

Cursor_Home equ b'00000010' ; 1.64mS , Return cursor to home position

ENTRY_DEC equ b'00000100' ; 40uS , Decrement cursor position & No display shift

ENTRY_DEC_S equ b'00000101' ; 40uS , Decrement cursor position & display shift

ENTRY_INC equ b'00000110' ; 40uS , Increment cursor position & No display shift

ENTRY_INC_S equ b'00000111' ; 40uS , Increment cursor position & display shift

DISP_OFF equ b'00001000' ; 40uS , Display off

DISP_ON equ b'00001100' ; 40uS , Display on control

DISP_ON_C equ b'00001110' ; 40uS , Display on, Cursor on

DISP_ON_B equ b'00001111' ; 40uS , Display on, Cursor on, Blink cursor

FUNC_SET equ b'00101000' ; 40uS , 4-bit interface , 2-lines & 5x7 dots

CG_RAM_ADDR equ b'01000000' ; 40uS , Least Significant 6-bit are for CGRAM address

DD_RAM_ADDR equ b'10000000' ; 40uS , Least Significant 7-bit are for DDRAM address

;

; Directs linker to provide 4 variables in GPR memory

UDATA

LCD_Byte RES 1

LCD_Temp RES 1

Count_uS RES 1

Count_mS RES 1

W_BUFR RES 1

Hex_Bfr RES 1

;

LCD_CODE CODE

;*******************************************************************

;* The LCD Module Subroutines                                      *

;* Command sequence for 2 lines of 5x16 characters                 *

;*******************************************************************

InitLCD

bcf LCD_E ; Clear LCD control line to Zero

bcf LCD_RW 

bcf LCD_RS 

;

bcf LCD_E_DIR ;configure control lines for Output pin

bcf LCD_RW_DIR

bcf LCD_RS_DIR

;

movlw b'00001110' ; configure AN0 as A/D inut pin

movwf ADCON1

movf LCD_CTRL,W ; get I/O directional settng

andlw 0xF0

movwf LCD_CTRL ; set LCD bus  DB[4:7] for output

;

movlw .50 ; Power-On delay 50mS

rcall Delay_xMS

;

movlw   b'00000011' ; #1 , Init for 4-bit interface

rcall Send_Low_4bit

;

movlw .10 ;  Delay 10 mS

rcall Delay_xMS

;

movlw b'00000011' ; #2 , Fully Initial LCD module 

rcall Send_Low_4bit ; Sent '0011' data  

rcall Delay_1mS

;

movlw b'00000011' ; #3 , Fully Initial LCD module 

rcall Send_Low_4bit ; Sent '0011' data  

rcall Delay_1mS

;

movlw b'00000010' ; #4 , Fully Initial LCD module 

rcall Send_Low_4bit ; Sent '0010' data  

rcall Delay_1mS

;

movlw FUNC_SET ; #5,#6 , Set 4-bit mode , 2 lines & 5 x 7 dots

rcall Send_Cmd

rcall Delay_1mS

;

movlw DISP_ON ; #7,#8 , Turn display on (0x0C)

rcall Send_Cmd

rcall Delay_1mS

;

movlw CLR_DISP ; #9,#10 , Clear LCD Screen

rcall Send_Cmd

movlw .5 ; Delay 5mS for Clear LCD Command execution

rcall Delay_xMS

;

movlw ENTRY_INC ; #11,#12 , Configure cursor movement

rcall Send_Cmd

rcall Delay_1mS

;

movlw DD_RAM_ADDR ; Set writes for display memory

rcall Send_Cmd

rcall Delay_1mS

;

return

;

;*******************************************************************

;*SendChar - Sends character to LCD                                *

;*This routine splits the character into the upper and lower       * 

;*nibbles and sends them to the LCD, upper nibble first.           *

;*******************************************************************

putcLCD

movwf LCD_Byte ; Save WREG in Byte variable

rcall Send_High_LCD ; Send upper nibble first

movf LCD_Byte,W

rcall Send_Low_LCD ; Send lower nibble data

rcall Delay_100uS

return

;

Send_High_LCD 

swapf WREG,W ; swap high/low nibble

Send_Low_LCD 

bcf LCD_RW ; set LCD Write Mode

andlw 0x0F ; Clear high nibble

movwf LCD_Temp

movf LCD_DATA,W ; Read back PORT

andlw 0xF0 ; keep data for PORTD[4:7]

iorwf LCD_Temp,W

movwf LCD_DATA ; Write data to LCD bus for low nibble bus DB[4:7]

bsf LCD_RS ; Set for data input

nop

bsf LCD_E ; Clock nibble into LCD

nop

bcf LCD_E

return

;

;*********************************************************************

;*      To put the HEX value to LCD Display ,,

;*      High nibble first than Low nibble 

;*      Input : W Reg.

;*********************************************************************

PutHexLCD

movwf W_BUFR ; Save W Register !!

swapf W_BUFR,W ; High nibble first !!

rcall Hex2ASCII

rcall putcLCD

;

movf W_BUFR,W

rcall Hex2ASCII

rcall putcLCD

return

;

;******************************************************************

;*       Convert a low nibble to ASCII code

;*       Input : W Reg.

;*       Output: W Reg.

;******************************************************************

Hex2ASCII

andlw 0x0f ; Mask Bit 4 to 7

movwf Hex_Bfr

sublw .09

btfsc STATUS,C ; If W less than A (C=1) --> only add 30h

bra _Add_W_30  

_Add_W_37 movlw 0x37

bra _Hex_cont 

_Add_W_30 movlw 0x30

_Hex_cont addwf Hex_Bfr,W ; The correct ASCII code for this char !!

return

;

;*******************************************************************

;* SendCmd - Sends command to LCD                                  *

;* This routine splits the command into the upper and lower        * 

;* nibbles and sends them to the LCD, upper nibble first.          *

;*******************************************************************

;     _    ______________________________

; RS  _>--<______________________________

;     _____

; RW       _____________________________

;                  __________________

; E   ____________/                  ___

;     _____________                ______

; DB  _____________>--------------<______

;

Send_Cmd

movwf LCD_Byte ; Save WREG in Byte variable

rcall Send_High_4bit ; Send upper nibble first

movf LCD_Byte,W

rcall Send_Low_4bit ; Send lower nibble data

rcall Delay_100uS

return

;

Send_High_4bit

swapf WREG,W ; swap high/low nibble

Send_Low_4bit

bcf LCD_RW ; set LCD Write Mode

andlw 0x0F ; Clear high nibble

movwf LCD_Temp

movf LCD_DATA,W ; Read back PORT

andlw 0xF0 ; keep data for PORTD[4:7]

iorwf LCD_Temp,W

movwf LCD_DATA ; Write data to LCD bus for low nibble bus DB[4:7]

bcf LCD_RS ; Clear for command inut

nop

bsf LCD_E ; Clock nibble into LCD

nop

bcf LCD_E

return

;

;*******************************************************************

;* clrLCD - Clear the contents of the LCD                          *

;*******************************************************************

clrLCD

movlw CLR_DISP ; Clear LCD screen

rcall Send_Cmd

movlw .5 ; Delay 5mS for Clear LCD Command execution

bra Delay_xMS

;

;*******************************************************************

;* L1homeLCD - Moves the cursor to home position on Line 1         *