Despatch Protocol Plus Modbus Communications - Manual (Page 50)

Chromalox Instruments and Controls
A-51643 Rev. 6 10/06/03 44
'set the Settings to select Baud Rate, Parity, Data bits, and Stop bits.
'Note that Baud Rate and Parity must match the Controller's settings,
'always use 8 Data bits and 2 Stop bits.
frmComm.comMain.Settings = "38400,N,8,2"
'set other parameters:
frmComm.comMain.InputLen = 0
frmComm.comMain.Handshaking = comNone
frmComm.comMain.InputMode = comInputModeText
frmComm.comMain.InBufferSize = 1024
frmComm.comMain.RThreshold = 1
frmComm.comMain.InputLen = 0
frmComm.comMain.OutBufferSize = 512
frmComm.comMain.SThreshold = 1
frmComm.comMain.EOFEnable = False
frmComm.comMain.ParityReplace = "?"
frmComm.comMain.NullDiscard = False
frmComm.comMain.RTSEnable = False
frmComm.comMain.DTREnable = True
'open the port:
frmComm.comMain.PortOpen = True
End Sub
The following procedure, placed to respond to the command button‘s click event, is used to build and
transmit a ―Read Holding Registers‖ message to read three registers starting at register 16:
Private Sub Command1_Click()
Dim CRCWord As Long 'CRC calculation result buffer
'initialize message with address, function, and function data bytes:
TxMessage = Chr(1) & Chr(3) & Chr(0) & Chr(16) & Chr(0) & Chr(3)
'call the CRC calculation: