Frontline’s “RS-422/485 ComProbe” – A Portable, Rugged and Easy-to-Use Device for monitoring Asynchronous RS-422/485 communications
To keep pace with advances in technology, the tried and true Serialtest®
analyzer has been upgraded to support the new "RS-422/485 ComProbe".
Most new laptops and PCs do not have PCMCIA interfaces and the PC
industry has migrated towards USB ports. To help our customers monitor
asynchronous serial communications via their PC's USB port, Frontline
has introduced its new RS-422/485 ComProbe II. This new device plugs
into a PC's USB port and has screw terminal connectors to tap into the
The RS-422/485 ComProbe monitors and captures Asynchronous RS-422/584
communications. It does not lose timing and control signal information.
With this new interface, Frontline has made its Serialtest analyzer more
rugged, easier to use, portable and transportable. It allows you to
spend more time doing your real job.
The new RS-422/485 ComProbe allows the user plenty of options for
monitoring various serial communication setups. The I/O Settings dialog
allows the user to configure the setup.
The RS-422/485 ComProbe supports data rates up to 921.6Kbps. The user
can pick one of the standard rates in the drop down box in the I/O
Settings dialog. For non-standard rates, the user can simply type in the
value in the box.
The RS-422/485 ComProbe can monitor serial communications with 5, 6, 7
or 8 data bits and with 1, 1.5 or 2 stop bits. The device also supports
all the standard parity types (None, Odd, Even, Mark, Space, and
The user can also choose the bit order on their serial communication
circuit. The choices are either LSB (least significant bit) first or MSB
(most significant bit) first. LSB first is normal, while MSB first is
considered "reversed" from normal. This option reverses the order of the
bits within each byte.
The user can also choose to monitor either DTE only, DCE only or both
DTE and DCE ends of the communication.
Pin Out and Cabling Information
The RS-422/485 ComProbe can be used for monitoring both 2-wire and 4-wire RS-422/485 communication circuits. The pin-out information for the RS-422/485 ComProbe is shown in the table below:
For 2-wire circuits, Serialtest expects to see the transmit lines of your circuit connected to the corresponding pins on the RS-422/485 ComProbe. Tap off of the Transmit + line (TX+) of your circuit, and connect that to pin 6 (RX+) on the RS-422/485 ComProbe, then tap off of the Transmit - line (TX-) and connect that to pin 7 (RX-) on the RS-422/485 ComProbe.
For a four wire circuit, the procedure is the same. Tap off of the Transmit + line (TX+) of your circuit, and connect that to pin 6 (RX+) on one ComProbe, then tap off of the Transmit ‐ line (TX‐) and connect that to pin 7 (RX‐) on the ComProbe. Do the same with the Receive lines, tap off of the RX+ and connect that to pin 1 on the ComProbe then tap RX‐ and send it to pin 2 on the ComProbe.
More details about wiring information for these configurations are
Frontline's new licensing scheme allows you to share the analyzer among
different platforms used by different individuals. A desktop user would
simply park his key, download it to his laptop and head to the remote
site exhibiting symptoms of a problem.
To learn more about testing, troubleshooting and debugging Serial communications
download a Serialtest demo.
You can also order your copy of