B&B Electronics MODSCAN32 - Manual - Manual (Page 72)

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Controls Overview
Modbuss.ocx contains 32-bit custom controls which allow Visual Basic and other OLE Container
applications to quickly and easily access data points contained in a modbus slave device connected to the
PC. The modbus device may be connected directly to a PC COM port or accessed via a network
connection using the modbus/TCP, communications protocol standard. Modem connections are also
supported using the Win32 TAPI interface. Multiple controls may be used within one application to access
multiple slave devices asynchronously.
Two controls are supplied with modbuss.ocx. The Serial Control, (Modbus Port Configuration Control), is
used to configure the physical operating characteristics of a PC COM port, (baud rate, parity, etc.), as well
as the modbus software protocol to be used, (RTU or ASCII).
The Modbus Data Control exposes properties which define the machine, COM port, slave device, point
address, and point type. These properties may be static, (defined when the control is created), or updated
programatically. Up to 128 integer data values, (64 floats), may be read from a device via each control.
Modbus data is presented to the controlling application as an array of values, (either Boolean, integer, or
float, depending on the specified point type).
RegSvr32
RegSvr32.exe is a DOS application supplied by Microsoft for making additions and changes to the
Windows Registry. Before the modbuss controls can be used by an application they must be properly
installed into the Registry. To do this, execute RegSvr32.exe and supply the full path name to the control as
an argument. The following command line shows how to register the modbuss control, (assuming the file is
contained in the C:\MODBUSS directory):
Regsvr32 c:\modbuss\modbuss.ocx
MbOCXsvr Helper Application
Modbuss.ocx controls operate in conjunction with two support applications supplied by WinTECH
Software. Modbusm.dll is responsible for the actual MODBUS message formatting logic and control of the
PC COM, TAPI, and network drivers. MbOCXsvr.exe is responsible for coordinating data traffic between
the dll and the control(s). To simplify the design of user applications, each Modbus Data Control appears
to have exclusive access to the designated set of IO data points. In effect, the system must be capable of
supporting multiple controls simultaneously. These controls may be located on the local machine or
possibly multiple remote machines. In addition, each control may, at any given point in time, reference data
from any device on any available COM port.
The mbOCXsvr application is a required component of the modbuss ocx control. Each time a Modbus Data
Control is started, it will attempt to start the mbOCXsvr application, (if not already running). As needed,
the control will request specific data from mbOCXsvr and this application is responsible for gathering the
data, (via modbusm.dll), and returning it to the control. If the mbOCXsvr application is terminated, the
controls will cease communication with the MODBUS device(s).
Menu options available from the mbOCXsvr application allow the user to configure the local serial port
setup parameters. The mbOCXsvr background display details statistical counters representing messaging
activity on each of the supported serial channels.