724-746-5500 | blackbox.com
Page 18
724-746-5500 | blackbox.com
3.2.2 RS-422
RS-422 connections support two signal pairs: TDA (-), TDB (+), RDA ( -), RDB (+), and GND. The data lines are differential pairs
(A and B) in which the B line is p ositive relative to the A line in the idle (mark) state. In R S-422, the transmitter is always enabled.
Signal Ground provides a common mode reference for the signal lines.
3.2.3 RS-485
RS-485 connections support 2-wire or 4 -wire operation. In RS-485 mode, the transmitter is only enabled when the Hardened
Serial Server is transmitting data on the line. This allows other devices to share the bus.
When configured for 4-wire operation, the connection supports two signal pairs: TDA (-), TDB (+), RDA (-), RDB (+), and GN D.
This makes full-duplex operation possible. The data lines are differential pairs (A and B) in which the B line is positive relative to
the A line in the idle (mark) state. Signal Ground provides a common mode reference for the signal lines.
When configured for 2-wire operation, the connection supports one signal pair: Data A (-) and Data B (+). These lines transmit
and receive signals using half-duplex operation. The data lines are differential with the Data B line positive relative to Data A in the
idle (mark) state. Signal Ground provides a common mode reference for the signal lines.
NOTE: Refer to Appendix B for connector pinout information.
Serial device
Serial connection
Network
Figure 3-2. LES424A connections.
3.3 Connecting RS-232/422/485 Hardened Serial Servers to a Network
Ethernet Connection (10BASE-T/100BASE-TX)
When connecting a Hardened Serial Server equipped with a 10BASE-T/100BASE-TX network connection (RJ-45 connec tor) to an
Ethernet network, use a standard unshielded twisted-pair cable. W hen installing this equipment in industrial or other electrically
noisy environments, we strongly recommend that you use STP (shielded twisted pair) cable. The Hardened Serial Server has an
automatic MDI-X interface that will sense the pinout of the network interface and provide a crossover connection if required.
3.4 Ethernet Passthrough Port
4-Port Hardened Serial Servers (LES424A) are equipped with an additional RJ-45 network port, also known as a
passthrough port. This port can be used to connect additional Ethernet devices, such as a local workstation or second serial
server, to the network.
Network
Local Ethernet
device
Figure 3-3. Ethernet passthrough port (on LES424A only).