Comtrol DeviceMaster LT User Manual page 116

Testing Comtrol COM Ports
116 - Troubleshooting and Technical Support
4. Click Driver, click RPSHSI/NSLINK.
5. If the DeviceMaster LT is communicating with the device driver for Windows,
Port Monitor should display CLOSED status. If a port is open for an
application, it displays as OPEN, and displays Actual Throughput, TxTotal and
RxTotal statistics.
Normally, there should be no data errors recorded or they should be very
small. To find out what the actual errors are, scroll to the right. You will see
three columns: Overrun Errors, Framing Errors, and Parity Errors.
If the errors are:
• Overrun Errors represent receive buffer overflow errors. If this is the case,
you will have to configure either software or hardware handshaking to
control the flow of data. The most common errors are Overrun errors.
• Framing Errors indicate that there is an synchronization error between the
beginning of a data frame and the end of the data frame. A frame usually
consists of a start bit, 8 data bits, and a stop bit or two. The framing error
occurs if the stop bit is not detected or it occurs in the wrong time frame.
Most causes for framing errors are electrical noise on the data lines, or
differences in the data clocks of the DeviceMaster LT and the connected
device.
• Parity Errors occur when parity is used and the parity bit is not what is
expected. This can also be caused by noise on the data lines.
DeviceMaster LT User Guide: 2000586 Rev. B