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CL4490 User’s Manual
Figure 7- DCE to DCE Interface
RI
OEM Host
NC
RI
NC
NC
NC
CL4490 Modem
DTR
D
C
D
DSR
DSR
DTR
D
C
D
GND
GND
RXD
TXD
TXD
RXD
RT
S
RT
S
CTS
C
T
S
DCE
DCE
Crossover Cable
Note: The Straight Through Cable provided with the CL4490 has female connectors on both ends
and the Crossover cable has a male connector at one end and a female connector at the other
end. Please use a male-to-male adapter or female-to-female adapter wherever required. Using
a null modem adapter with a Crossover cable is equivalent to using a Straight Through cable.
1.5 RS-485 (2-wire Half Duplex)
The RS-485 interface uses a Differential Data Transmission that can help nullify the effects of
ground shifts and induced noise signals that can appear as common mode voltages on a
network.
The CL4490 implements a RS-485 (2-wire Half Duplex) multi-drop interface. Typically, a RS-485
bus will consist of a master and several slaves. The nodes will have unique addresses and can
send addressed packets to specific nodes. Because the bus is half duplex, no two nodes should
try to talk at the same time. The CL4490 does not have a RS-485 address, therefore, it will
transmit all RS-485 traffic over the RF. Conversely, as soon as a CL4490 receives a packet over
the RF, it will transmit the packet over the RS-485 bus.
Note: When using RS-485 (2-wire Half Duplex), a RS-485 to RS-232 converter is required to
configure the unit. AeroComm recommends a B&B Electronics 4WSD9R converter to translate
RS-485 to RS-232.
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