vb编写的modbus rtu协议通讯源程序（VB written in Modbus RTU protocol source code）.doc

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vb编写的modbus rtu协议通讯源程序（VB written in Modbus RTU protocol source code）.doc

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vb编写的modbus rtu协议通讯源程序（VB written in Modbus RTU protocol source code）

vb编写的modbus rtu协议通讯源程序（VB written in Modbus RTU protocol source code） VB written in Modbus RTU protocol source code Sunwu proposed to delete the post!! | collection | reply | modification 2005-12-09 12:37:09 | landlord Modbus RTU protocol can be regarded as a de facto standard protocol, is supported by many instruments, such as PLC. Previously, several users asked how to use VB programming to communicate with our KND-K3 family of PLC, so they completed a demo program. This time, share this demo, I hope to give you some help. 1) module file: modCRC, which contains the function of CRC checksum. data the name of the array to be checked Number of elements in aNo array btLoCRC calculated CRC high byte btHiCRC calculated CRC low byte Public, Function, CalCRC16Fast (data (), As, Byte, no, As, Integer, btLoCRC, As, Byte, btHiCRC, As, Byte) As String Dim, CL, As, Byte, CH, As, Byte, polynomial codes, HA001 Dim, SaveHi, As, Byte, SaveLo, As, Byte Dim I As Integer Dim Flag As Integer BtHiCRC = HFF BtLoCRC = HFF CL = H1 CH = HA0 For I = 0 To (no - 1) BtHiCRC = btHiCRC, Xor, data (I) , each data is XOR with the CRC register For Flag = 0, To 7 SaveHi = btLoCRC SaveLo = btHiCRC BtLoCRC = btLoCRC \ 2 \ high right shift one BtHiCRC = btHiCRC \ 2 , move right one low If ((SaveHi, And, H1) = H1) Then if the upper byte last bit is 1 BtHiCRC = btHiCRC, Or, H80 , then move the low byte to the right, then fill 1 in the front End If , otherwise auto fill 0 If ((SaveLo, And, H1) = H1) Then if LSB is 1, then it is XOR with polynomial code BtLoCRC = btLoCRC, Xor, CH BtHiCRC = btHiCRC, Xor, CL End If Next Flag Next I Dim ReturnData (1) As Byte ReturnData (0) = btHiCRC,CRC high ReturnData (1) = btLoCRCCRC low CalCRC16Fast = ReturnData End Function Public, Function, CalCRC16Tbl (data (), As, Byte, no, As, Integer, btLoCRC, As, Byte, btHiCRC, As, Byte) As String Dim btLoCRC As Byte Dim btHiCRC As Byte BtLoCRC = HFF BtHiCRC = HFF Dim I As Integer Dim iIndex As Long For I = 0 To (no - 1) IIndex = b