PIC16Fxxx的LCD驅(qū)動(dòng)程序(適用于HD44780兼容的驅(qū)動(dòng)器)

;************************************************
;* LCD.ASM                                      *
;************************************************
;* Contains subroutines to control an external  *
;* lcd panel in 4-bit mode.  These routines     *
;* were designed specifically for the panel on  *
;* the MCU201 workshop 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=16f877
  ＃i nclude <p16f877.inc>
;
; Defines for I/O ports that provide LCD data & control
; PORTB.0 - PORTB.3 are Data Pins for LCD Module
; PORTB.4 is E Control Signal for LCD
; PORTB.5 is RS Control Signal for LCD
; PORTC.2 is BackLight Control pin for LCD Module
;
  global InitLCD
  global putcLCD
  global clrLCD
  global L1homeLCD
  global L2homeLCD
  global  SendCmd
  global PutHexLCD
  global Hex2ASCII
;
LCD_DATA equ PORTB
LCD_CNTL equ PORTB

; Defines for I/O pins that provide LCD control
RS  equ 5
E  equ 4

; LCD Module commands
DISP_ON  EQU 0x00C ; Display on
DISP_ON_C EQU 0x00E ; Display on, Cursor on
DISP_ON_B EQU 0x00F ; Display on, Cursor on, Blink cursor
DISP_OFF EQU 0x008 ; Display off
CLR_DISP EQU 0x001 ; Clear the Display
ENTRY_INC EQU 0x006 ;
ENTRY_INC_S EQU 0x007 ;
ENTRY_DEC EQU 0x004 ;
ENTRY_DEC_S EQU 0x005 ;
DD_RAM_ADDR EQU 0x080 ; Least Significant 7-bit are for address
DD_RAM_UL EQU 0x080 ; Upper Left coner of the Display
;

; Directs linker to provide 4 variables in GPR memory
  UDATA
Byte  RES 1
Byte1  RES 1
Count  RES 1
Count1  RES 1
W_BUFR  RES 1
Hex_Bfr   RES 1
;
PROG1  CODE 
;*******************************************************************
;* The LCD Module Subroutines                                      *
;* Command sequence for 2 lines of 5x16 characters                 *
;*******************************************************************
InitLCD
  BANKSEL TRISB
  movlw 0xc0  ; Initialize inputs/outputs for LCD
  movwf TRISB
  BANKSEL LCD_DATA
  clrf LCD_DATA ; Clear LCD data & control bits
;
  movlw .50  ; Power=On delay 50mS
  Call  Delay_MS
;
  movlw   0x02  ; Init for 4-bit interface
  call Send_4bit
  movlw .10  ;  Delay 10 mS
  Call  Delay_MS
;
  movlw b'00000011' ; Fully Initial LCD module
  call Send_4bit ; Sent '0011' data 4 time
  movlw .5  ; Delay 5mS
  Call  Delay_MS
  movlw b'00000011'
  call Send_4bit
  call Delay_1MS ; Delay 1mS
   movlw b'00000011'
   call Send_4bit
   movlw b'00000010'
   call Send_4bit
;
  movlw b'00101000' ; Set 2 lines & 5 x 7 dots
  call SendCmd
  movlw DISP_ON  ; Turn display on (0x0C)
  call SendCmd
  movlw ENTRY_INC ; Configure cursor movement
  call SendCmd
  movlw DD_RAM_ADDR ; Set writes for display memory
  call SendCmd
  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
  banksel Byte
  movwf Byte  ; Save WREG in Byte variable
  call Delay_1MS
  swapf Byte,W  ; Write upper nibble first
  andlw 0x0f
  movwf LCD_DATA
  bsf LCD_CNTL, RS ; Set for data
  bsf LCD_CNTL, E ; Clock nibble into LCD
  bcf LCD_CNTL, E
  movf Byte,W  ; Write lower nibble last
  andlw 0x0f
  movwf LCD_DATA
  bsf LCD_CNTL, RS ; Set for data
  bsf LCD_CNTL, E ; Clock nibble into LCD
  bcf LCD_CNTL, E
  return[!--empirenews.page--]
;
;*********************************************************************
;*      To put the HEX value to LCD Display ,,
;*      High nibble first than Low nibble
;*      Input : W Reg.
;*********************************************************************
PutHexLCD
  banksel W_BUFR
  movwf W_BUFR  ; Save W Register !!
  swapf W_BUFR,W  ; High nibble first !!
  call Hex2ASCII
  call putcLCD
;
  movf W_BUFR,W
  call Hex2ASCII
  call 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
  goto Add_W_30 
Add_W_37 movlw 0x37
  goto 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.          *
;*******************************************************************
SendCmd
  banksel Byte
  movwf Byte  ; Save WREG in Byte variable
  call Delay_1MS
  swapf Byte,W  ; Send upper nibble first
  andlw 0x0f
  movwf LCD_DATA
  bcf LCD_CNTL,RS ; Clear for command
  bsf LCD_CNTL,E ; Clock nibble into LCD
  bcf LCD_CNTL,E
  movf Byte,W  ; Write lower nibble last
Send_4bit andlw 0x0f
  movwf LCD_DATA
  bcf LCD_CNTL,RS ; Clear for command
  bsf LCD_CNTL,E ; Clock nibble into LCD
  bcf LCD_CNTL,E
  return
;
;*******************************************************************
;* clrLCD - Clear the contents of the LCD                          *
;*******************************************************************
clrLCD
  movlw CLR_DISP ; Send the command to clear display
  call SendCmd
  return
;
;*******************************************************************
;* L1homeLCD - Moves the cursor to home position on Line 1         *
;*******************************************************************
L1homeLCD
  movlw DD_RAM_ADDR|0x00 ; Send command to move cursor to
  call SendCmd   ; home position on line 1
  return

;*******************************************************************
;* L2homeLCD - Moves the cursor to home position on Line 2         *
;*******************************************************************
L2homeLCD
  movlw DD_RAM_ADDR|0x28 ; Send command to move cursor to
  call SendCmd   ; home position on line 2
  return

;*******************************************************************
;* Delay - Generic LCD delay  (1.024mS @ 4MHz)                     *
;* Since the microcontroller can not read the busy flag of the     *
;* LCD, a specific delay needs to be executed between writes to    *
;* the LCD.                                                        *
;*******************************************************************
Delay_1MS    ; 2 cycles for call
  clrf Count  ; 1 cycle to clear counter variable
Dloop
  nop
  decfsz Count,F  ; These two instructions provide a
  goto Dloop  ; (256 * 3) -1 cycle count
  return   ; 2 cycles for return
;
;*******************************************************************
;*       Delay - 1mS base delay        *
;*       input : W Reg.                                            *
;*                                                                 *
;*******************************************************************
Delay_MS
  movwf Count1
;
DLop1  call Delay_1MS
  decfsz Count1,F
  goto DLop1
  return
;
  END