read_s7_300_real.bas

可以读些S7-300PLC中的变量数据

Attribute VB_Name = "Module1"
'*************************************************************************************
Public Function Read_S7_300_Real(DecimalInput As Long) As Double
'------------------十进制转二进制------------------------------------------------
Dim HighBit As Long '转换成二进制的最高位数
Dim AndResult As Long  '相与后的结果

Dim BinaryString As String
Dim DecimalConvertBinary As String
Dim float_count(1024)
BinaryString = ""
HighBit = 1073741824
            While (HighBit > 0.5) '
                AndResult = HighBit And DecimalInput
                If (AndResult <> 0) Then
                    BinaryString = BinaryString + "1"
                    Else
                    BinaryString = BinaryString + "0"
                End If
                HighBit = HighBit / 2 '每次右移一位
            Wend
        DecimalConvertBinary = BinaryString '存储的是二进制数的字符串
'******************************************************************************************
'-------------截取二进制位-----------------------------------------------------------------------------

Binary_String = Trim(DecimalConvertBinary)

BinaryStrLength = Len(Binary_String)

E_Binary_Length = BinaryStrLength - 23

E_Binary_Str = Left(Binary_String, E_Binary_Length)

E_Decimal = BinaryConvertDecimal(E_Binary_Str)

Exponent = E_Decimal - 127 '计算出的指数

Mantissa_Binary = Right(Binary_String, 23) '计算出的尾数

Mantissa = BinaryConvertDecimal(Mantissa_Binary)

'********************************************************************************************************
'---------------------------------------------------------------------------------------------



  j = 1 'j
  mm = 0
            s1 = 0
            While (j < 8388608)
                k = j And Mantissa
                If (k <> 0) Then
                    s1 = 1
                    Else
                    s1 = 0
                End If
            float_count(mm) = s1
            mm = mm + 1
                j = j * 2 '1,2,4,8,16,32,64,128,256...移动要相或的位数
                
            Wend
        
        x = float_count(0)
        For Index = 1 To 23
        x = Round(x / 2 + float_count(Index), 5)
        
        
   
Next Index
bb = Round(x, 5)
Read_S7_300_Real = (bb + 1) * 2 ^ Exponent
End Function

Public Function BinaryConvertDecimal(ByVal varString As String) As Long
          Dim Slen     As Long
          Dim i     As Long
          Dim returnNum     As Long
          Slen = Len(varString)
          For i = 0 To Slen - 1
                  returnNum = returnNum + Val(Mid(varString, i + 1, 1)) * (2 ^ (Slen - i - 1))
          Next
          BinaryConvertDecimal = returnNum
  End Function