14 Troubleshooting Guide
7. Check the Device Manager for error messages.
8. Run Hyper Terminal, and open the serial port of NetCom
+
device. Use the loopback plug
to see the Echo of your typing. Use a Null Modem cable, and connect it from COM1 to the
NetCom
+
. Open a second Window of Hyper Terminal for COM1. Send some data between
these two windows. Transfer a file using ZMODEM protocol.
9. Often so-called Personal Firewall programs cause unspecific errors when other software starts
communicating. Check the documentation of the program to see how to allow access.
10. If some special function is not operative, check for the proper version of the Firmware. In
case of doubt install the latest version available (
http://www.vscom.de/
).
11. In rare cases or on special hardware the driver for Windows may have a problem. Please
load and install the latest version (
http://www.vscom.de/
) and try again. It is necessary to
uninstall the previous version.
12. Transmissions on IP-networks impose some extra delay in transmit and receive times. These
can add to between 5 and 10 milliseconds, depending on configurations. Such delays may
cause applications to complain about non-functional hardware, in fact it is a protocol/delay
problem.
13. Wireless Connections may fail if the Access Point does not broadcast the SSID. The NetCom
+
Servers need the broadcast to get the parameters from the Access Point. Hiding the SSID is
not a security feature anyway.
14. Many other problems occur because of a failed serial connection, caused by wrong cabling.
Here are some frequent causes.
a) The serial cable in RS 232 mode may simply be to long. This mostly happens with
higher transmission rates.
b) In RS 422 and RS 485 it is mandatory to also connect the GND signal of all devices. It is
a very frequent error not to do this. The information is transferred (and defined) by the
positive or negative difference of the Data+ and Data- lines. However the specification
requires a common voltage range between the connected devices. To ensure this range
the connection of GND is required.
c) A network in RS 485 requires biasing resistors (polarization). The Data+ line requires
a pull-up resistor to +5V, and the Data- line needs a pull-down resistor to GND. The
value is about 750Ω to 1 kΩ. When no station is transmitting, the Data-lines float. This
will cause noise and strange errors. The biasing resistors place a differential voltage
to the lines, at least 200 mV. These resistors must not exist on the network more than
once. Therefore they are not enabled in the NetCom
+
serial ports. To enable them it is
necessary to open the case, and set the Jumpers (see section
3.3
).
September 2016
NetCom Plus User Manual
128
