LCD Character 4-bit Interface

LCD character 4-bit Interface sample code. 

'---------------------------------------------------------
'
'4_bit_character.bas
'Program For Writing To Newhaven Display Character LCD
'
' (c) Newhaven Display International, Inc.
'
'  This program is free software; you can redistribute it and/or modify
' it under the terms of the GNU General Public License as published by
' the Free Software Foundation; either version 2 of the License, or
' (at your option) any later version.
'
' This program is distributed in the hope that it will be useful,
' but WITHOUT ANY WARRANTY; without even the implied warranty of
' MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
' GNU General Public License for more details.
'
'---------------------------------------------------------
'2x16 Dot-Matrix Module
'4 Bit interface
'
'DB7-DB4 is P1.7-P1.4
'E is P3.4  active LOW
'WR is P3.7 ***GND***
'D/I is P3.0
'
'-----------------------------------------------------------------------------
Declare Sub Writecom
Declare Sub Writedata
Declare Sub Nybble

Dim A As Byte
Dim Com As Byte
Dim Count As Byte

'Start'
Do

Set P3
Reset P3.0
Waitms 100
A = &H30
P1 = A
Call Nybble                                                   'wake up
Waitms 100
Call Nybble                                                   'wake up
Waitms 10
Call Nybble                                                   'wake up
Waitms 10
A = &H20                                                      '4-bit interface
P1 = A
Call Nybble
Com = &H28                                                    '4-bit, 2 lines
Call Writecom
Com = &H10                                                    'cursor shift
Call Writecom
Com = &H0F                                                    'display on
Call Writecom
Com = &H06                                                    'entry mode
Call Writecom

Com = &H01                                                    'home
Call Writecom
Restore Dta1
For Count = 1 To 16
 Read A
 Call Writedata
Next Count
Com = &HC0                                                    '2nd line
Call Writecom
Restore Dta2
For Count = 1 To 16
 Read A
 Call Writedata
Next Count

Wait 5
Loop
End

Dta1:
Data "Newhaven Display"
Dta2:
Data "4-bit interface "

Sub Nybble
Reset P3.4                                                    'E
Waitms 1                                                      'enable pulse width  >= 300ns
Set P3.4                                                      'E
End Sub

Sub Writecom
P1 = Com                                                      'move data to Port 1
Reset P3.0                                                    'RS = Instruction register
Call Nybble                                                   'write high 4 bits
Rotate Com , Left , 4                                         'rotate
P1 = Com                                                      'move data to Port 1
Call Nybble                                                   'write low 4 bits
End Sub

Sub Writedata
P1 = A
Set P3.0                                                      'RS=Data register
Call Nybble
Rotate A , Left , 4
P1 = A
Call Nybble
End Sub