Advantech ADAM-5550KW Series, Руководство пользователя

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Appendix A RS-485 Network
ADAM-5510KW Series User’s Manual A- 3
A.1 Basic Network Layout
Multi-drop RS-485 implies that there are two main wires in a
segment. The connected systems tap from these two lines
with so called drop cables. Thus all connections are parallel
and connecting or discon- necting of a node doesn’t affect
the network as a whole. Since ADAM-5550KW Series
Controller use the RS-485 standard, they can connect and
communicate with the host PC. The basic layouts that can be
used for an RS-485 network are:
Daisychain
The last module of a segment is a repeater. It is directly
connected to the main-wires thereby ending the first segment
and starting the next segment. Up to 32 addressable systems
can be daisychained . This limitation is a physical one. When
using more systems per segment the IC driver current rapidly
decreases, causing communication errors. In total, the
network can hold up to 64 addressable systems. The limita-
tion on this number is the two-character hexadecimal address
code that can address 64 combinations. The ADAM converter,
ADAM repeaters and the host computer are non addressable
units and therefore are not included in these numbers.
Figure A-1: Daisychaining