B&B Electronics VFG3000 - Manual - Manual (Page 41)

A DVANCED C OMMUNICATIONS S HARING S ERIAL P ORTS
R EVISION 1 P AGE 25
TCP/IP port number of the serial port that you have shared. In the example below, we are
routing data from the programming port to a PLC that is connected via the RS-232 comms
port…
Note that the Baud rate and other port settings do not have to be the same as those for the port
which we are sharing. In the configuration shown above, data to and from the programming
software is sent at a higher Baud rate than the data to and from the PLC, with the Gateway
doing the appropriate buffering and conversion.
In this example, to make use of the shared port you would connect a spare serial port on your
PC to the programming port of the Gateway, and configure the PLC programming software to
talk to this COM port. As soon as the PC begins to talk to the PLC, communications between
the Gateway and the PLC will be suspended, and the Gateway’s two ports will be
“connected” in software, such that the PC will appear to be talking directly to the PLC. If no
data is transferred for more than a minute, communications between the Gateway and the
PLC will be resumed.
C ONNECTING VIA E THERNET
Rather than using an additional serial port on your PC and on the Gateway, it is possible to
use a third-party utility to create what are known as virtual serial ports on your computer.
These appear to applications to be physical COM ports, but in fact, they send and receive data
to a remote device over TCP/IP. By installing one of these utilities and configuring it to
address the Gateway, you can have serial access to any devices connected to the Gateway
without any additional cabling. Indeed, there is no need to have any physical serial ports
available on the PC at all—something that is very valuable when working with modern
laptops, where a COM port is often an expensive option.
Several third-party virtual serial port utilities are available. On the freeware side, a company
called HW Group (http://www.hw-group.com) provides a utility called HW Virtual Serial
Port. There are also a number of other freeware port drivers available, most of which seem to
be derived from the same source base. On the commercial side, a company called Tactical
Software (http://www.tacticalsoftware.com) offers Serial/IP for about $100 a port.
While the various freeware drivers no doubt have many contented users, we have found that
these drivers have occasional stability problems on certain PCs. Tactical Software’s Serial/IP