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BASCOM AVR, help reference (2007).PDF

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DECLARE FUNCTION

Action

Declares a user function.

Syntax

DECLARE FUNCTION TEST[( [BYREF/BYVAL] var as type)] As type

Remarks

test	Name of the function.
Var	Name of the variable(s).
Type	Type of the variable(s) and of the result. Byte,Word, Integer, Long,
	Single or String. Bits are not supported.

When BYREF or BYVAL is not provided, the parameter will be passed by reference. Use BYREF to pass a variable by reference with its address.

Use BYVAL to pass a copy of the variable.

See the CALL statement for more details.

You must declare each function before writing the function or calling the function. And the declaration must match the function.

Bits are global and can not be passed with functions or subs.

When you want to pass a string, you pass it with it's name : string. So the size is not important. For example :

Declare function Test(s as string, byval z as string) as byte

DECLARE SUB

Action

Declares a subroutine.

Syntax

DECLARE SUB TEST[( [BYREF/BYVAL] var as type)]

Remarks

test	Name of the procedure.
Var	Name of the variable(s).
Type	Type of the variable(s). Byte, Word, Integer, Long, Single or String.

page -449-

When BYREF or BYVAL is not provided, the parameter will be passed by reference. Use BYREF to pass a variable by reference with its address.

Use BYVAL to pass a copy of the variable.

See the CALL statement for more details.

You must declare each function before writing the function or calling the function. And the declaration must match the function.

Bits are global and can not be passed with functions or subs.

See also

CALL, SUB , FUNCTION

Example

'-----------------------------------------------------------------------------
------------	: declare.bas
'name	: declare.bas
'copyright	: (c) 1995-2005, MCS Electronics
'purpose	: demonstrate using declare
'micro	: Mega48
'suited for demo	: yes
'commercial addon needed	: no
' Note that the usage of SUBS works different in BASCOM-8051
'-----------------------------------------------------------------------------
------------
$regfile = "m48def.dat"	' specify the used
micro	' used crystal
$crystal = 4000000	' used crystal
frequency	' use baud rate
$baud = 19200	' use baud rate
$hwstack = 32	' default use 32
for the hardware stack	' default use 10
$swstack = 10	' default use 10
for the SW stack	' default use 40
$framesize = 40	' default use 40
for the frame space

' First the SUB programs must be declared

'Try a SUB without parameters

Declare Sub Test2

'SUB with variable that can not be changed(A) and

'a variable that can be changed(B1), by the sub program

'When BYVAL is specified, the value is passed to the subprogram

'When BYREF is specified or nothing is specified, the address is passed to 'the subprogram

Declare Sub Test(byval A As Byte , B1 As Byte) Declare Sub Testarray(byval A As Byte , B1 As Byte) 'All variable types that can be passed

'Notice that BIT variables can not be passed. 'BIT variables are GLOBAL to the application

Declare Sub Testvar(b As Byte , I As Integer , W As Word , L As Long , S As String)

'passing string arrays needs a different syntax because the length of the

page -450-

strings must be passed by the compiler

'the empty () indicated that an array will be passed

Declare Sub Teststr(b As Byte , Dl() As String)

Dim Bb As Byte , I As Integer , W As Word , L As Long , S As String * 10

'dim used variables
Dim Ar(10) As Byte	'strng array
Dim Sar(10) As String * 8	'strng array
For Bb = 1 To 10	'fill the array
Sar(bb) = Str(bb)	'fill the array
Next

Bb = 1

'now call the sub and notice that we always must pass the first address with index 1

Call Teststr(bb , Sar(1))

Call Test2	'call sub
Test2	'or use without
CALL
'Note that when calling a sub without the statement CALL, the enclosing
parentheses must be left out
Bb = 1	'call sub with
Call Test(1 , Bb)	'call sub with
parameters	'print value that
Print Bb	'print value that
is changed
'now test all the variable types
Call Testvar(bb , I , W , L , S )
Print Bb ; I ; W ; L ; S
'now pass an array
'note that it must be passed by reference
Testarray 2 , Ar(1)
Print "ar(1) = " ; Ar(1)
Print "ar(3) = " ; Ar(3)
$notypecheck	' turn off type
checking
Testvar Bb , I , I , I , S
'you can turn off type checking when you want to pass a block of memory
$typecheck	'turn it back on
End

'End your code with the subprograms

'Note that the same variables and names must be used as the declared ones

Sub Test(byval A As Byte , B1 As Byte)	'start sub
Print A ; " " ; B1	'print passed
variables	'change value
B1 = 3	'change value
'You can change A, but since a copy is passed to the SUB,
'the change will not reflect to the calling variable
End Sub
Sub Test2	'sub without
parameters
Print "No parameters"
End Sub

Sub Testvar(b As Byte , I As Integer , W As Word , L As Long , S As String)

page -451-

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'-----------------------------------------------------------------------------
------------	: function.bas
'name	: function.bas
'copyright	: (c) 1995-2005, MCS Electronics
'purpose	: demonstration of user function
'micro	: Mega48
'suited for demo	: yes
'commercial addon needed	: no

	© MCS Electronics, 1995-2007
for the hardware stack	' default use 10
$swstack = 10	' default use 10
for the SW stack	' default use 40
$framesize = 40	' default use 40
for the frame space