Mikrodenetleyici
dünyasında, pratik kullanımda insan ile etkileşimde büyük bir önemi olan LCD
göstergeri yönetmek ve kullanmak gereklidir. Aşağıda PIC 16F84A ile gerçekleştirilmiş
bir devre ve bunun ASM Örnek olarak aşağıdaki devrede mikrodenetleyiciye
besleme, XT osilatör eklenmiştir. Bundan sonra ortak anotlu 7 segment displayin
8 bacağına PIC’in B Portları bağlanmıştır.
LCD Arayüzünün Gerçekleştirilmiş Hali
LCD Arayüzü Devre Şeması
LCD Assembly Programı
LIST
P=16F84A, F=INHX8M
; ERRORLEVEL 2
__CONFIG
_CP_OFF & _WDT_OFF & _XT_OSC
;include
#include
"p16f84A.inc"
;*****************************************************************************
RESET_V EQU 0x0000 ; Address of RESET Vector
ISR_V EQU 0x0004 ;
Address of Interrupt Vector
OSC_FREQ EQU D'4000000' ; Oscillator Frequency is 4 MHz
LCD_DATA EQU PORTB ; LCD data lines interface
LCD_DATA_TRIS EQU TRISB
LCD_CTRL EQU PORTA ; LCD control lines interface
LCD_LINE0 EQU 0x000
LCD_LINE1 EQU 0x040
LCD_LINE2 EQU 0x014
LCD_LINE3 EQU 0x054
; PORTA bits
LCD_E EQU 2 ;
LCD Enable control line
LCD_RW EQU 1 ; LCD Read/Write control line
LCD_RS EQU 0 ; LCD Register-Select control line
; PORTB bits
DB7 EQU 7 ;
LCD dataline 7 (MSB)
DB6 EQU 6 ;
LCD dataline 6
DB5 EQU 5 ;
LCD dataline 5
DB4 EQU 4 ;
LCD dataline 4
DB3 EQU 3 ;
LCD dataline 3
DB2 EQU 2 ;
LCD dataline 2
DB1 EQU 1 ;
LCD dataline 1
DB0 EQU 0 ;
LCD dataline 0 (LSB)
; misc.
LCD_TEMP EQU 0x020 ; LCD subroutines internal use
TABLE_INDEX EQU 0x021 ; Index to table strings
COUNT EQU 0x022 ;
A counter
DELAY equ 0x023 ;
Used in DELAYxxx routines
X_DELAY equ 0x024 ; Used in X_DELAYxxx routines
;*****************************************************************************
; Program Baslangic
;*****************************************************************************
ORG RESET_V ;
RESET vector location
RESET GOTO START
;*****************************************************************************
ORG ISR_V ;
Interrupt vector location
INTERRUPT BCF STATUS, RP0 ; Select bank 0
GOTO INTERRUPT
;*****************************************************************************
START ;
POWER_ON Reset (Beginning of program)
CLRF STATUS ;
Do initialization, Select bank 0
CLRF INTCON ;
Clear int-flags, Disable interrupts
CLRF PCLATH ;
Keep in lower 2KByte
CLRF PORTA ;
ALL PORT output should output Low.
CLRF PORTB
BSF STATUS, RP0 ;
Select bank 1
MOVLW 0x0F8 ;
RA2-0 outputs, RA4-3 inputs
MOVWF TRISA
MOVLW 0x000 ;
RB7-0 outputs
MOVWF TRISB
BSF OPTION_REG, NOT_RBPU
;
Disable PORTB pull-ups
BCF STATUS, RP0 ;
Select bank 0
CALL LCDINIT ;
Initialize LCDisplay
;*****************************************************************************
; Display some lines, here
MOVLW 0x030 ;
ASCII '0'
MOVWF COUNT
MOVLW LCD_LINE0
CALL LCDSDDA ;
Position cursor leftmost on first line
CALL TABLE_MSG ;
Display message
MOVLW LCD_LINE0 + 0x013
CALL LCDSDDA ;
Position cursor
MOVF COUNT, W
CALL LCDPUTCHAR ;
Display line number
INCF COUNT, F
MOVLW LCD_LINE1
CALL LCDSDDA
CALL TABLE_MSG2
MOVLW LCD_LINE1 + 0x013
CALL LCDSDDA
MOVF COUNT, W
CALL LCDPUTCHAR
INCF COUNT, F
MOVLW LCD_LINE2
CALL LCDSDDA
CALL TABLE_MSG
MOVLW LCD_LINE2 + 0x013
CALL LCDSDDA
MOVF COUNT, W
CALL LCDPUTCHAR
INCF COUNT, F
MOVLW LCD_LINE3
CALL LCDSDDA
CALL TABLE_MSG
MOVLW LCD_LINE3 + 0x013
CALL LCDSDDA
MOVF COUNT, W
CALL LCDPUTCHAR
;*****************************************************************************
; Program ends here
;*****************************************************************************
LOOP
GOTO LOOP ;
Stay here forever
;*****************************************************************************
; Send a message using a table to
output a message
;*****************************************************************************
TABLE_MSG
MOVLW 0 ;
Startindex of table message
DISP_MSG
MOVWF TABLE_INDEX ;
Holds message address
CALL MSG1
ANDLW 0x0FF ;
Check if at end of message
BTFSC STATUS, Z ;
(zero returned at end)
GOTO TABLE_MSG_END
CALL LCDPUTCHAR ;
Display character
MOVF TABLE_INDEX, W ; Point to next character
ADDLW 1
GOTO DISP_MSG
TABLE_MSG_END RETURN
;*****************************************************************************
; Send a message using a table to
output a message
; OK
;*****************************************************************************
TABLE_MSG2
MOVLW 0 ;
Startindex of table message
DISP_MSG2
MOVWF TABLE_INDEX ;
Holds message address
CALL MSG2
ANDLW 0x0FF ;
Check if at end of message
BTFSC STATUS, Z ;
(zero returned at end)
GOTO TABLE_MSG2_END
CALL LCDPUTCHAR ;
Display character
MOVF TABLE_INDEX, W ; Point to next character
ADDLW 1
GOTO DISP_MSG2
TABLE_MSG2_END RETURN
;*****************************************************************************
; LCD Module Subroutines
;*****************************************************************************
;
;=============================================================================
; LCDINIT
; Initilize LC-Display Module
; Should be modified to your needs
(i.e. display type, cursor on/off, etc.)
; OK
;=============================================================================
LCDINIT
;
Busy-flag is not yet valid
CLRF LCD_CTRL ;
ALL PORT output should output Low.
;
power-up delay
MOVLW 0x01E
CALL X_DELAY500 ;
30 * 0.5mS = 15mS
;
Busy Flag should be valid from here
MOVLW 0x038 ;
8-bit-interface, 2-lines
CALL LCDPUTCMD
MOVLW 0x000 ;
disp.off, curs.off, no-blink
CALL LCDDMODE
CALL LCDCLEAR
MOVLW 0x004 ;
disp.on, curs.off
CALL LCDDMODE
MOVLW 0x002 ;
auto-inc (shift-cursor)
CALL LCDEMODE
RETURN
;=============================================================================
; LCD_ENABLE
; Pulses LCD enable pin
; OK
;=============================================================================
LCD_ENABLE
BSF LCD_CTRL, LCD_E ; LCD E-line High
BCF LCD_CTRL, LCD_E ; LCD E-line Low
RETURN
;=============================================================================
; LCDBUSY
; Returns when LCD busy-flag is
inactive
; OK
;=============================================================================
LCDBUSY
BSF STATUS,RP0 ;
Select Register page 1
MOVLW 0x0FF ;
Set PORTB for input
MOVWF LCD_DATA_TRIS
BCF STATUS, RP0 ;
Select Register page 0
BCF LCD_CTRL, LCD_RS; Set LCD for command mode
BSF LCD_CTRL, LCD_RW; Setup to read busy flag
BSF LCD_CTRL, LCD_E ; LCD E-line High
MOVF LCD_DATA, W ;
Read busy flag + DDram address
BCF LCD_CTRL, LCD_E ; LCD E-line Low
ANDLW 0x80 ;
Check Busy flag, High = Busy
BTFSS STATUS, Z
GOTO LCDBUSY
LCDNOTBUSY BCF LCD_CTRL, LCD_RW
BSF STATUS, RP0 ;
Select Register page 1
MOVLW 0x000
MOVWF LCD_DATA_TRIS ;
Set PORTB for output
BCF STATUS, RP0 ;
Select Register page 0
RETURN
;=============================================================================
; LCDCLEAR
; Clears display and returns cursor
to home position (upper-left corner).
;
;=============================================================================
LCDCLEAR
MOVLW 0x001
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDHOME
; Returns cursor to home position.
; Returns display to original
position (when shifted).
;
;=============================================================================
LCDHOME
MOVLW 0x002
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDEMODE
; Sets entry mode of display.
; Required entry mode must be set in
W
;
b0 : 0 = no display shift 1 = display shift
;
b1 : 0 = auto-decrement 1 = auto-increment
;
b2-7 : don't care
; OK
;=============================================================================
LCDEMODE
ANDLW 0x003 ;
Strip upper bits
IORLW 0x004 ;
Function set
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDDMODE
; Sets display control.
; Required display mode must be set
in W
;
b0 : 0 = cursor blink off 1 = cursor blink on
;
b1 : 0 = cursor off 1 = cursor on
;
b2 : 0 = display off 1 = display on (display data remains in
DDRAM)
;
b3-7 : don't care
; OK
;=============================================================================
LCDDMODE
ANDLW 0x007 ;
Strip upper bits
IORLW 0x008 ;
Function set
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDSCGA
; Sets Character-Generator-RAM
address. CGRAM is read/written after
;
this setting.
; Required CGRAM address must be set
in W
;
b0-5 : required CGRAM address
;
b6-7 : don't care
;
;=============================================================================
LCDSCGA
ANDLW 0x03F ;
Strip upper bits
IORLW 0x040 ;
Function set
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDSDDA
; Sets the Display-Data-RAM address.
DDRAM data is read/written after
;
this setting.
; Required DDRAM address must be set
in W
;
b0-6 : required DDRAM address
;
b7 : don't care
; OK
;=============================================================================
LCDSDDA
IORLW 0x080 ;
Function set
CALL LCDPUTCMD
RETURN
;=============================================================================
; LCDGADDR
; Returns address counter contents,
used for both DDRAM and CGRAM.
; RAM address is returned in W
;
;=============================================================================
LCDGADDR
BSF STATUS,RP0 ;
Select Register page 1
MOVLW 0x0FF ;
Set PORTB for input
MOVWF LCD_DATA_TRIS
BCF STATUS, RP0 ;
Select Register page 0
BCF LCD_CTRL, LCD_RS; Set LCD for command mode
BSF LCD_CTRL, LCD_RW; Setup to read busy flag
BSF LCD_CTRL, LCD_E ; LCD E-line High
MOVF LCD_DATA, W ;
Read busy flag + RAM address
BCF LCD_CTRL, LCD_E ; LCD E-line Low
ANDLW 0x07F ;
Strip upper bit
BCF LCD_CTRL, LCD_RW
BSF STATUS, RP0 ;
Select Register page 1
MOVLW 0x000
MOVWF LCD_DATA_TRIS ;
Set PORTB for output
BCF STATUS, RP0 ;
Select Register page 0
RETURN
;=============================================================================
; LCDPUTCHAR
; Sends character to LCD
; Required character must be in W
; OK
;=============================================================================
LCDPUTCHAR
MOVWF LCD_TEMP ;
Character to be sent is in W
CALL LCDBUSY ;
Wait for LCD to be ready
BCF LCD_CTRL, LCD_RW; Set LCD in read mode
BSF LCD_CTRL, LCD_RS; Set LCD in data mode
BSF LCD_CTRL, LCD_E ; LCD E-line High
MOVF LCD_TEMP, W
MOVWF LCD_DATA ;
Send data to LCD
BCF LCD_CTRL, LCD_E ; LCD E-line Low
RETURN
;=============================================================================
; LCDPUTCMD
; Sends command to LCD
; Required command must be in W
; OK
;=============================================================================
LCDPUTCMD
MOVWF LCD_TEMP ;
Command to be sent is in W
CALL LCDBUSY ;
Wait for LCD to be ready
BCF LCD_CTRL, LCD_RW; Set LCD in read mode
BCF LCD_CTRL, LCD_RS; Set LCD in command mode
BSF LCD_CTRL, LCD_E ; LCD E-line High
MOVF LCD_TEMP, W
MOVWF LCD_DATA ;
Send data to LCD
BCF LCD_CTRL, LCD_E ; LCD E-line Low
RETURN
;*****************************************************************************
; Delay_time = ((DELAY_value * 3) + 4) * Cycle_time
; DELAY_value = (Delay_time - (4 * Cycle_time)) / (3 * Cycle_time)
;
; i.e. (@ 4MHz crystal)
; Delay_time = ((32 * 3) + 4) * 1uSec
; =
100uSec
; DELAY_value = (500uSec - 4) / 3
; =
165.33
; =
165
;*****************************************************************************
DELAY500 MOVLW D'165' ; +1 1
cycle
MOVWF DELAY ;
+2 1 cycle
DELAY500_LOOP DECFSZ DELAY, F ; step 1 1
cycle
GOTO DELAY500_LOOP ;
step 2 2 cycles
DELAY500_END RETURN ; +3 2 cycles
;
;
X_DELAY500 MOVWF X_DELAY ; +1 1 cycle
X_DELAY500_LOOP CALL DELAY500 ; step1 wait
500uSec
DECFSZ X_DELAY, F ;
step2 1 cycle
GOTO X_DELAY500_LOOP ; step3 2
cycles
X_DELAY500_END RETURN ; +2 2 cycles
;=============================================================================
; Table message to display
;=============================================================================
MSG1
addwf PCL ,F ;Jump
to char pointed to in W reg
retlw 'H'
retlw 'a'
retlw 'l'
retlw 'i'
retlw 'c'
retlw ' '
retlw 'U'
retlw 'n'
retlw 'i'
retlw '.'
retlw ' '
retlw ' '
retlw '2'
retlw '0'
retlw '0'
retlw '9'
retlw ' '
retlw ' '
retlw ' '
retlw '#'
MSG1_END
retlw 0
;
IF
( (MSG1 & 0x0FF) >= (MSG1_END & 0x0FF) )
MESSG "Warning - User Definded: Table 'MSG1'
crosses page boundry in computed jump"
ENDIF
MSG2
addwf PCL ,F ;Jump
to char pointed to in W reg
retlw ' '
retlw ' '
retlw ' '
retlw 'U'
retlw 'm'
retlw 'u'
retlw 't'
retlw ' '
retlw 'S'
retlw 'I'
retlw 'M'
retlw 'S'
retlw 'E'
retlw 'K'
retlw ' '
retlw ' '
retlw ' '
retlw ' '
retlw ' '
retlw '#'
MSG2_END
retlw 0
;
IF
( (MSG2 & 0x0FF) >= (MSG2_END & 0x0FF) )
MESSG
"Warning - User Definded: Table
'MSG1' crosses page boundry in computed jump"
ENDIF
END ; End of program
