Public Class Form1
    Public Declare Function Inp Lib "inpout32.dll" Alias "Inp32" (ByVal _
      PortAddress As Integer) As Integer
    Public Declare Sub Out Lib "inpout32.dll" Alias "Out32" (ByVal PortAddress _
    As Integer, ByVal Value As Integer)
    Dim impz As Int32                    'Impulszähler
    Dim spannung As Int32 = 1
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        'Dim test As Int32 = Inp(889) And 8                   'Pin 15-Test  ( _
        jeweils 1 durch 8 ers.)
        Dim test As Int32 = Inp(888) And 1                    'D0 Test
        If spannung = 1 And test = 0 Then
            impz += 1                                         'Zähler erhöhen
            Me.Text = impz                                    'Wert anzeigen
            spannung = 0
        End If
        If spannung = 0 And test = 1 Then spannung = 1
    End Sub
    Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer2.Tick
        Out(888, Inp(888) Xor 1)                  '50 Hz-Testgenerator um D0 
        ' umschalten
    End Sub
End Class