How to use an LCD text module.

LCD Command Control Codes Command Binary Hex 
D7 D6 D5 D4 D3 D2 D1 D0 
Clear Display 0 0 0 0 0 0 0 1 01 
Display and Cursor Home 0 0 0 0 0 0 1 x 02 or 03 
Character Entry Mode 0 0 0 0 0 1 I/D S 01 to 07 
Display On/Off and Cursor 0 0 0 0 1 D U B 08 to 0F 
Display/Cursor Shift 0 0 0 1 D/C R/L x x 10 to 1F 
Function Set 0 0 1 8/4 2/1 10/7 x x 20 to 3F 
Set CGRAM Address 0 1 A A A A A A 40 to 7F 
Set Display Address 1 A A A A A A A 80 to FF 
I/D: 1=Increment* 0=Decrement 
S: 1=Display Shift On 0=Display Shift off* 
D: 1=Display On 0=Display Off* 
U: 1=Cursor Underline On 0=Cursor Underline Off* 
B: 1=Cursor Blink On 0=Cursor Blink Off* 
D/C: 1=Display Shift 0=Cursor Move 
R/L: 1=Right Shift 0=Left Shift 
8/4: 1=8 bit interface* 0=4 bit interface 
2/1: 1=2 line mode 0=1 line mode* 
10/7: 1=5x10 dot format 0=5x7 dot format* 

*=initialisation setting x=don't care 


This table shows the command codes for the LCD module, it was taken from an excellent LCD tutorial that was published in the UK magazine 'Everyday Practical Electronics' February 1997 - it can be downloaded as a PDF file from the EPE website. The following routines are an amalgamation of a number of routines from various sources (including the previously mentioned tutorial), plus various parts of my own, the result is a set of reliable, easy to use, routines which work well (at least in my opinion!).

Tutorial 3.1 - requires Main Board and LCD Board.

This program displays a text message on the LCD module, it consists mostly of subroutines for using the LCD module.

;LCD text demo - 4 bit mode
;Nigel Goodwin 2002

LIST p=16F628 ;tell assembler what chip we are using
include "P16F628.inc" ;include the defaults for the chip
ERRORLEVEL 0, -302 ;suppress bank selection messages
__config 0x3D18 ;sets the configuration settings (oscillator type etc.)




cblock 0x20 ;start of general purpose registers
count ;used in looping routines
count1 ;used in delay routine
counta ;used in delay routine
countb ;used in delay routine
tmp1 ;temporary storage
tmp2
templcd ;temp store for 4 bit mode
templcd2 
endc

LCD_PORT Equ PORTA
LCD_TRIS Equ TRISA
LCD_RS Equ 0x04 ;LCD handshake lines
LCD_RW Equ 0x06
LCD_E Equ 0x07

org 0x0000

movlw 0x07
movwf CMCON ;turn comparators off (make it like a 16F84)

Initialise clrf count
clrf PORTA
clrf PORTB



SetPorts bsf STATUS, RP0 ;select bank 1
movlw 0x00 ;make all pins outputs
movwf LCD_TRIS
bcf STATUS, RP0 ;select bank 0

call Delay100 ;wait for LCD to settle


call LCD_Init ;setup LCD


clrf count ;set counter register to zero
Message movf count, w ;put counter value in W
call Text ;get a character from the text table
xorlw 0x00 ;is it a zero?
btfsc STATUS, Z
goto NextMessage
call LCD_Char
call Delay255
incf count, f
goto Message

NextMessage call LCD_Line2 ;move to 2nd row, first column

clrf count ;set counter register to zero
Message2 movf count, w ;put counter value in W
call Text2 ;get a character from the text table
xorlw 0x00 ;is it a zero?
btfsc STATUS, Z
goto EndMessage
call LCD_Char
incf count, f
goto Message2

EndMessage 

Stop goto Stop ;endless loop




;Subroutines and text tables

;LCD routines

;Initialise LCD
LCD_Init movlw 0x20 ;Set 4 bit mode
call LCD_Cmd

movlw 0x28 ;Set display shift
call LCD_Cmd

movlw 0x06 ;Set display character mode
call LCD_Cmd

movlw 0x0d ;Set display on/off and cursor command
call LCD_Cmd

call LCD_Clr ;clear display

retlw 0x00

; command set routine
LCD_Cmd movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high
call Delay5
retlw 0x00

LCD_CharD addlw 0x30
LCD_Char movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high
call Delay5
retlw 0x00

LCD_Line1 movlw 0x80 ;move to 1st row, first column
call LCD_Cmd
retlw 0x00

LCD_Line2 movlw 0xc0 ;move to 2nd row, first column
call LCD_Cmd
retlw 0x00

LCD_Line1W addlw 0x80 ;move to 1st row, column W
call LCD_Cmd
retlw 0x00

LCD_Line2W addlw 0xc0 ;move to 2nd row, column W
call LCD_Cmd
retlw 0x00

LCD_CurOn movlw 0x0d ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_CurOff movlw 0x0c ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_Clr movlw 0x01 ;Clear display
call LCD_Cmd
retlw 0x00

LCD_HEX movwf tmp1
swapf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
movf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
retlw 0x00

Delay255 movlw 0xff ;delay 255 mS
goto d0
Delay100 movlw d'100' ;delay 100mS
goto d0
Delay50 movlw d'50' ;delay 50mS
goto d0
Delay20 movlw d'20' ;delay 20mS
goto d0
Delay5 movlw 0x05 ;delay 5.000 ms (4 MHz clock)
d0 movwf count1
d1 movlw 0xC7 ;delay 1mS
movwf counta
movlw 0x01
movwf countb
Delay_0
decfsz counta, f
goto $+2
decfsz countb, f
goto Delay_0

decfsz count1 ,f
goto d1
retlw 0x00

Pulse_e bsf LCD_PORT, LCD_E
nop
bcf LCD_PORT, LCD_E
retlw 0x00

;end of LCD routines

HEX_Table ADDWF PCL , f
RETLW 0x30
RETLW 0x31
RETLW 0x32
RETLW 0x33
RETLW 0x34
RETLW 0x35
RETLW 0x36
RETLW 0x37
RETLW 0x38
RETLW 0x39
RETLW 0x41
RETLW 0x42
RETLW 0x43
RETLW 0x44
RETLW 0x45
RETLW 0x46


Text addwf PCL, f
retlw 'H'
retlw 'e'
retlw 'l'
retlw 'l'
retlw 'o'
retlw 0x00

Text2 ADDWF PCL, f
RETLW 'R'
RETLW 'e'
RETLW 'a'
RETLW 'd'
RETLW 'y'
RETLW '.'
RETLW '.'
RETLW '.'
RETLW 0x00


end 

As usual, first we need to set things up, after the normal variable declarations and port setting we reach 'call LCD_Init', this sets up the LCD module. It first waits for 100mS to give the module plenty of time to settle down, we then set it to 4 bit mode (0x20) and set the various options how we want them - in this case, Display Shift is On (0x28), Character Entry Mode is Increment (0x06), and Block Cursor On (0x0D). Once the LCD is setup, we can then start to send data to it, this is read from a table, exactly the same as the LED sequencer in the earlier tutorials - except this time we send the data to the LCD module (using LCD_Char) and use a 0x00 to mark the end of the table, thus removing the need to maintain a count of the characters printed. Once the first line is displayed we then sent a command to move to the second line (using call LCD_Line2), and then print the second line from another table. After that we enter an endless loop to leave the display as it is.

This program introduces a new use of the 'goto' command, 'goto $+2' - '$' is an MPASM arithmetic operator, and uses the current value of the program counter, so 'goto $+2' means jump to the line after the next one - 'goto $+1' jumps to the next line, and may seem pretty useless (as the program was going to be there next anyway), but it can be extremely useful. A program branch instruction (like goto) uses two instruction cycles, whereas other instructions only take one, so if you use a 'nop' in a program it takes 1uS to execute, and carries on from the next line - however, if you use 'goto $+1' it still carries on from the next line, but now takes 2uS. You'll notice more use of the 'goto $' construction in later tutorials, if you are checking an input pin and waiting for it to change state you can use 'goto $-1' to jump back to the previous line, this saves allocating a label to the line that tests the condition.

This is a table of the LCD subroutines provided in these programs, you can easily add more if you wish - for instance to set a line cursor rather than a block one, if you find you are using a particular feature a lot you may as well make a subroutine for it.

LCD Subroutines LCD_Init Initialise LCD Module 
LCD_Cmd Sent a command to the LCD 
LCD_CharD Add 0x30 to a byte and send to the LCD
(to display numbers as ASCII) 
LCD_Char Send the character in W to the LCD 
LCD_Line1 Go to start of line 1 
LCD_Line2 Go to start of line 2 
LCD_Line1W Go to line 1 column W 
LCD_Line2W Go to line 2 column W 
LCD_CurOn Turn block cursor on 
LCD_CurOff Turn block cursor off 
LCD_Clr Clear the display 
LCD_HEX Display the value in W as Hexadecimal 

Tutorial 3.2 - requires Main Board and LCD Board.

This program displays a text message on the top line and a running 16 bit counter on the bottom line, with the values displayed in both decimal and hexadecimal , it consists mostly of the previous subroutines for using the LCD module, plus an extra one for converting from 16 bit hexadecimal to decimal.

;LCD 16 bit counter
;Nigel Goodwin 2002

LIST p=16F628 ;tell assembler what chip we are using
include "P16F628.inc" ;include the defaults for the chip
ERRORLEVEL 0, -302 ;suppress bank selection messages
__config 0x3D18 ;sets the configuration settings (oscillator type etc.)




cblock 0x20 ;start of general purpose registers
count ;used in looping routines
count1 ;used in delay routine
counta ;used in delay routine
countb ;used in delay routine
tmp1 ;temporary storage
tmp2
templcd ;temp store for 4 bit mode
templcd2

NumL ;Binary inputs for decimal convert routine
NumH 

TenK ;Decimal outputs from convert routine
Thou 
Hund 
Tens 
Ones 
endc

LCD_PORT Equ PORTA
LCD_TRIS Equ TRISA
LCD_RS Equ 0x04 ;LCD handshake lines
LCD_RW Equ 0x06
LCD_E Equ 0x07

org 0x0000

movlw 0x07
movwf CMCON ;turn comparators off (make it like a 16F84)

Initialise clrf count
clrf PORTA
clrf PORTB
clrf NumL
clrf NumH



SetPorts bsf STATUS, RP0 ;select bank 1
movlw 0x00 ;make all pins outputs
movwf LCD_TRIS
bcf STATUS, RP0 ;select bank 0

call LCD_Init ;setup LCD


clrf count ;set counter register to zero
Message movf count, w ;put counter value in W
call Text ;get a character from the text table
xorlw 0x00 ;is it a zero?
btfsc STATUS, Z
goto NextMessage
call LCD_Char
incf count, f
goto Message

NextMessage call LCD_Line2 ;move to 2nd row, first column

call Convert ;convert to decimal
movf TenK, w ;display decimal characters
call LCD_CharD ;using LCD_CharD to convert to ASCII
movf Thou, w
call LCD_CharD
movf Hund, w
call LCD_CharD 
movf Tens, w
call LCD_CharD
movf Ones, w
call LCD_CharD
movlw ' ' ;display a 'space'
call LCD_Char
movf NumH, w ;and counter in hexadecimal
call LCD_HEX
movf NumL, w
call LCD_HEX
incfsz NumL, f
goto Next
incf NumH, f
Next call Delay255 ;wait so you can see the digits change
goto NextMessage


;Subroutines and text tables

;LCD routines

;Initialise LCD
LCD_Init call Delay100 ;wait for LCD to settle

movlw 0x20 ;Set 4 bit mode
call LCD_Cmd

movlw 0x28 ;Set display shift
call LCD_Cmd

movlw 0x06 ;Set display character mode
call LCD_Cmd

movlw 0x0c ;Set display on/off and cursor command
call LCD_Cmd ;Set cursor off

call LCD_Clr ;clear display

retlw 0x00

; command set routine
LCD_Cmd movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high
call Delay5
retlw 0x00

LCD_CharD addlw 0x30 ;add 0x30 to convert to ASCII
LCD_Char movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high
call Delay5
retlw 0x00

LCD_Line1 movlw 0x80 ;move to 1st row, first column
call LCD_Cmd
retlw 0x00

LCD_Line2 movlw 0xc0 ;move to 2nd row, first column
call LCD_Cmd
retlw 0x00

LCD_Line1W addlw 0x80 ;move to 1st row, column W
call LCD_Cmd
retlw 0x00

LCD_Line2W addlw 0xc0 ;move to 2nd row, column W
call LCD_Cmd
retlw 0x00

LCD_CurOn movlw 0x0d ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_CurOff movlw 0x0c ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_Clr movlw 0x01 ;Clear display
call LCD_Cmd
retlw 0x00

LCD_HEX movwf tmp1
swapf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
movf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
retlw 0x00

Delay255 movlw 0xff ;delay 255 mS
goto d0
Delay100 movlw d'100' ;delay 100mS
goto d0
Delay50 movlw d'50' ;delay 50mS
goto d0
Delay20 movlw d'20' ;delay 20mS
goto d0
Delay5 movlw 0x05 ;delay 5.000 ms (4 MHz clock)
d0 movwf count1
d1 movlw 0xC7 ;delay 1mS
movwf counta
movlw 0x01
movwf countb
Delay_0
decfsz counta, f
goto $+2
decfsz countb, f
goto Delay_0

decfsz count1 ,f
goto d1
retlw 0x00

Pulse_e bsf LCD_PORT, LCD_E
nop
bcf LCD_PORT, LCD_E
retlw 0x00

;end of LCD routines

HEX_Table ADDWF PCL , f
RETLW 0x30
RETLW 0x31
RETLW 0x32
RETLW 0x33
RETLW 0x34
RETLW 0x35
RETLW 0x36
RETLW 0x37
RETLW 0x38
RETLW 0x39
RETLW 0x41
RETLW 0x42
RETLW 0x43
RETLW 0x44
RETLW 0x45
RETLW 0x46


Text addwf PCL, f
retlw '1'
retlw '6'
retlw ' '
retlw 'B'
retlw 'i'
retlw 't'
retlw ' '
retlw 'C'
retlw 'o'
retlw 'u'
retlw 'n'
retlw 't'
retlw 'e'
retlw 'r'
retlw '.'
retlw 0x00

;This routine downloaded from http://www.piclist.com
Convert: ; Takes number in NumH:NumL
; Returns decimal in
; TenK:Thou:Hund:Tens:Ones
swapf NumH, w
iorlw B'11110000'
movwf Thou
addwf Thou,f
addlw 0XE2
movwf Hund
addlw 0X32
movwf Ones

movf NumH,w
andlw 0X0F
addwf Hund,f
addwf Hund,f
addwf Ones,f
addlw 0XE9
movwf Tens
addwf Tens,f
addwf Tens,f

swapf NumL,w
andlw 0X0F
addwf Tens,f
addwf Ones,f

rlf Tens,f
rlf Ones,f
comf Ones,f
rlf Ones,f

movf NumL,w
andlw 0X0F
addwf Ones,f
rlf Thou,f

movlw 0X07
movwf TenK

; At this point, the original number is
; equal to
; TenK*10000+Thou*1000+Hund*100+Tens*10+Ones
; if those entities are regarded as two's
; complement binary. To be precise, all of
; them are negative except TenK. Now the number
; needs to be normalized, but this can all be
; done with simple byte arithmetic.

movlw 0X0A ; Ten
Lb1:
addwf Ones,f
decf Tens,f
btfss 3,0
goto Lb1
Lb2:
addwf Tens,f
decf Hund,f
btfss 3,0
goto Lb2
Lb3:
addwf Hund,f
decf Thou,f
btfss 3,0
goto Lb3
Lb4:
addwf Thou,f
decf TenK,f
btfss 3,0
goto Lb4

retlw 0x00


end 

Tutorial 3.3 - requires Main Board and LCD Board.

This program displays a text message on the top line and a running 16 bit counter on the bottom line, just as the last example, however, instead of using the Delay calls this version waits until the LCD Busy flag is clear. The LCD module takes time to carry out commands, these times vary, and the previous tutorials used a delay more than long enough to 'make sure' - however, the modules have the capability of signalling when they are ready, this version uses that facility and avoids any unnecessary delays. I've also used the LCD_Line2W routine to position the numbers further to the right and demonstrate the use of the routine, another slight change is that the tables have been moved to the beginning of program memory, this was done because it's important that tables don't cross a 256 byte boundary, so putting them at the start avoids this.

;LCD 16 bit counter - using LCD Busy line
;Nigel Goodwin 2002

LIST p=16F628 ;tell assembler what chip we are using
include "P16F628.inc" ;include the defaults for the chip
ERRORLEVEL 0, -302 ;suppress bank selection messages
__config 0x3D18 ;sets the configuration settings (oscillator type etc.)




cblock 0x20 ;start of general purpose registers
count ;used in looping routines
count1 ;used in delay routine
counta ;used in delay routine
countb ;used in delay routine
tmp1 ;temporary storage
tmp2
templcd ;temp store for 4 bit mode
templcd2

NumL ;Binary inputs for decimal convert routine
NumH 

TenK ;Decimal outputs from convert routine
Thou 
Hund 
Tens 
Ones 
endc

LCD_PORT Equ PORTA
LCD_TRIS Equ TRISA
LCD_RS Equ 0x04 ;LCD handshake lines
LCD_RW Equ 0x06
LCD_E Equ 0x07

org 0x0000
goto Start

HEX_Table ADDWF PCL , f
RETLW 0x30
RETLW 0x31
RETLW 0x32
RETLW 0x33
RETLW 0x34
RETLW 0x35
RETLW 0x36
RETLW 0x37
RETLW 0x38
RETLW 0x39
RETLW 0x41
RETLW 0x42
RETLW 0x43
RETLW 0x44
RETLW 0x45
RETLW 0x46


Text addwf PCL, f
retlw '1'
retlw '6'
retlw ' '
retlw 'B'
retlw 'i'
retlw 't'
retlw ' '
retlw 'C'
retlw 'o'
retlw 'u'
retlw 'n'
retlw 't'
retlw 'e'
retlw 'r'
retlw '.'
retlw 0x00

Start movlw 0x07
movwf CMCON ;turn comparators off (make it like a 16F84)

Initialise clrf count
clrf PORTA
clrf PORTB
clrf NumL
clrf NumH



SetPorts bsf STATUS, RP0 ;select bank 1
movlw 0x00 ;make all pins outputs
movwf LCD_TRIS
movwf TRISB
bcf STATUS, RP0 ;select bank 0

call LCD_Init ;setup LCD


clrf count ;set counter register to zero
Message movf count, w ;put counter value in W
call Text ;get a character from the text table
xorlw 0x00 ;is it a zero?
btfsc STATUS, Z
goto NextMessage
call LCD_Char
incf count, f
goto Message

NextMessage movlw d'2'
call LCD_Line2W ;move to 2nd row, third column

call Convert ;convert to decimal
movf TenK, w ;display decimal characters
call LCD_CharD ;using LCD_CharD to convert to ASCII
movf Thou, w
call LCD_CharD
movf Hund, w
call LCD_CharD 
movf Tens, w
call LCD_CharD
movf Ones, w
call LCD_CharD
movlw ' ' ;display a 'space'
call LCD_Char
movf NumH, w ;and counter in hexadecimal
call LCD_HEX
movf NumL, w
call LCD_HEX
incfsz NumL, f
goto Next
incf NumH, f
Next call Delay255 ;wait so you can see the digits change
goto NextMessage


;Subroutines and text tables

;LCD routines

;Initialise LCD
LCD_Init call LCD_Busy ;wait for LCD to settle

movlw 0x20 ;Set 4 bit mode
call LCD_Cmd

movlw 0x28 ;Set display shift
call LCD_Cmd

movlw 0x06 ;Set display character mode
call LCD_Cmd

movlw 0x0c ;Set display on/off and cursor command
call LCD_Cmd ;Set cursor off

call LCD_Clr ;clear display

retlw 0x00

; command set routine
LCD_Cmd movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bcf LCD_PORT, LCD_RS ;RS line to 0
call Pulse_e ;Pulse the E line high
call LCD_Busy
retlw 0x00

LCD_CharD addlw 0x30 ;add 0x30 to convert to ASCII
LCD_Char movwf templcd
swapf templcd, w ;send upper nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high

movf templcd, w ;send lower nibble
andlw 0x0f ;clear upper 4 bits of W
movwf LCD_PORT
bsf LCD_PORT, LCD_RS ;RS line to 1
call Pulse_e ;Pulse the E line high
call LCD_Busy
retlw 0x00

LCD_Line1 movlw 0x80 ;move to 1st row, first column
call LCD_Cmd
retlw 0x00

LCD_Line2 movlw 0xc0 ;move to 2nd row, first column
call LCD_Cmd
retlw 0x00

LCD_Line1W addlw 0x80 ;move to 1st row, column W
call LCD_Cmd
retlw 0x00

LCD_Line2W addlw 0xc0 ;move to 2nd row, column W
call LCD_Cmd
retlw 0x00

LCD_CurOn movlw 0x0d ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_CurOff movlw 0x0c ;Set display on/off and cursor command
call LCD_Cmd
retlw 0x00

LCD_Clr movlw 0x01 ;Clear display
call LCD_Cmd
retlw 0x00

LCD_HEX movwf tmp1
swapf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
movf tmp1, w
andlw 0x0f
call HEX_Table
call LCD_Char
retlw 0x00

Delay255 movlw 0xff ;delay 255 mS
goto d0
Delay100 movlw d'100' ;delay 100mS
goto d0
Delay50 movlw d'50' ;delay 50mS
goto d0
Delay20 movlw d'20' ;delay 20mS
goto d0
Delay5 movlw 0x05 ;delay 5.000 ms (4 MHz clock)
d0 movwf count1
d1 movlw 0xC7 ;delay 1mS
movwf counta
movlw 0x01
movwf countb
Delay_0
decfsz counta, f
goto $+2
decfsz countb, f
goto Delay_0

decfsz count1 ,f
goto d1
retlw 0x00

Pulse_e bsf LCD_PORT, LCD_E
nop
bcf LCD_PORT, LCD_E
retlw 0x00

LCD_Busy
bsf STATUS, RP0 ;set bank 1
movlw 0x0f ;set Port for input
movwf LCD_TRIS
bcf STATUS, RP0 ;set bank 0
bcf LCD_PORT, LCD_RS ;set LCD for command mode
bsf LCD_PORT, LCD_RW ;setup to read busy flag
bsf LCD_PORT, LCD_E
swapf LCD_PORT, w ;read upper nibble (busy flag)
bcf LCD_PORT, LCD_E 
movwf templcd2 
bsf LCD_PORT, LCD_E ;dummy read of lower nibble
bcf LCD_PORT, LCD_E
btfsc templcd2, 7 ;check busy flag, high = busy
goto LCD_Busy ;if busy check again
bcf LCD_PORT, LCD_RW
bsf STATUS, RP0 ;set bank 1
movlw 0x00 ;set Port for output
movwf LCD_TRIS
bcf STATUS, RP0 ;set bank 0
return

;end of LCD routines



;This routine downloaded from http://www.piclist.com
Convert: ; Takes number in NumH:NumL
; Returns decimal in
; TenK:Thou:Hund:Tens:Ones
swapf NumH, w
iorlw B'11110000'
movwf Thou
addwf Thou,f
addlw 0XE2
movwf Hund
addlw 0X32
movwf Ones

movf NumH,w
andlw 0X0F
addwf Hund,f
addwf Hund,f
addwf Ones,f
addlw 0XE9
movwf Tens
addwf Tens,f
addwf Tens,f

swapf NumL,w
andlw 0X0F
addwf Tens,f
addwf Ones,f

rlf Tens,f
rlf Ones,f
comf Ones,f
rlf Ones,f

movf NumL,w
andlw 0X0F
addwf Ones,f
rlf Thou,f

movlw 0X07
movwf TenK

; At this point, the original number is
; equal to
; TenK*10000+Thou*1000+Hund*100+Tens*10+Ones
; if those entities are regarded as two's
; complement binary. To be precise, all of
; them are negative except TenK. Now the number
; needs to be normalized, but this can all be
; done with simple byte arithmetic.

movlw 0X0A ; Ten
Lb1:
addwf Ones,f
decf Tens,f
btfss 3,0
goto Lb1
Lb2:
addwf Tens,f
decf Hund,f
btfss 3,0
goto Lb2
Lb3:
addwf Hund,f
decf Thou,f
btfss 3,0
goto Lb3
Lb4:
addwf Thou,f
decf TenK,f
btfss 3,0
goto Lb4

retlw 0x00


end