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LBC-4000 L-Band Up/Down Converter System
Serial Interface Operation
browser (for use of the LBC-4000 HTTP Interface).
The LBC-4000 Management IP Address has been noted using the
•
serial interface. (The firmware information (i.e., revision letters,
version numbers, etc.) as shown may differ from your setup.)
8.1.2
EIA-485
For applications where multiple devices are to be monitored and controlled, a
full-duplex (4-wire plus ground) EIA-485 is preferred. Half-duplex (2-wire plus
ground) EIA-485 is possible, but is not preferred. In full-duplex EIA-485
communication, there are two separate, isolated, independent, differential-
mode twisted pairs, each handling serial data in different directions.
It is assumed that a 'Controller' device (a PC or dumb terminal) transmits data in
a broadcast mode via one of the pairs. Many 'Target' devices are connected to
this pair, and all simultaneously receive data from the Controller. The Controller
is the only device with a line-driver connected to this pair; the Target devices
have only line-receivers connected.
In the other direction: On the other pair, each Target has a Tri-state line driver
connected; the Controller has a line-receiver connected. All the line drivers are
held in high-impedance mode until one – and only one – Target transmits back to
the Controller. Each Target has a unique address; each time the Controller
transmits, the address of the intended recipient Target is included in a framed
'packet' of data. All of the Targets receive the packet, but only one (the
intended) will reply. The Target enables its output line driver and transmits its
return data packet back to the Controller in the other direction on the physically
separate pair.
EIA-485 (full duplex) summary: Two differential pairs – one pair for Controller-to-
Target, one pair for Target-to-Controller.
• The Controller-to-Target pair has one line driver (Controller), and all
Targets have line-receivers.
• The Target-to-Controller pair has one line receiver (Controller), and all
Targets have Tri-state drivers.
8–2
MN/LBC4000.IOM
Revision 5
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