Advantech ADAM-5550KW Series, Руководство пользователя

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Appendix A RS-485 Network
A-2 ADAM-5510KW Series User’s Manual
EIA RS-485 is the industry’s most widely used bidirectional,
balanced transmission line standard. It is specifically developed
for industrial multi-drop systems that should be able to transmit
and receive data at high rates or over long distances.
The specifications of the EIA RS-485 protocol are as follows:
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Maximum line length per segment: 1200 meters (4000
feet)
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Throughput of 10 Mbaud and beyond -Differential
transmission
(balanced lines) with high resistance against noise
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Maximum 32 nodes per segment
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Bi-directional master-slave communication over a
single set of twisted-pair cables
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Parallel connected nodes, true multi-drop
ADAM-5550KW Series Controller is fully isolated and use just a
single set of twisted pair wires to send and receive! Since the
nodes are connected in parallel they can be freely disconnected
from the host without affecting the functioning of the remaining
nodes. An industry standard, shielded twisted pair is preferable
due to the high noise ratio of the environment. When nodes
communicate through the network, no sending conflicts can
occur since a simple command/response sequence is used.
There is always one initiator (with no address) and many slaves
(with addresses). In this case, the master is a personal
computer that is connected with its serial, RS-232, port to an
ADAM RS-232/RS-485 converter. The slaves are the
ADAM-5550KW Series Controller. When systems are not
transmitting data, they are in listen mode. The host computer
initiates a command/response sequence with one of the
systems. Commands normally contain the address of the
module the host wants to communicate with. The system with
the matching address carries out the command and sends its
response to the host.