Distech Controls ECLYPSE APEX, Руководство пользователя

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158 ECLYPSE APEX
Typical Modbus RTU
Device
Typical Modbus RTU
Device
Typical Modbus RTU
Device
Typical Modbus RTU
Device
EOL ON
EOL OFF
EOL OFF
EOL OFF
Data Bus: Shielded Twisted Pair Cable
Electrical
System
Ground
Baud: Auto (Factory Default) Baud: Auto (Factory Default) Baud: Auto (Factory Default) Baud: 38 400
Baud: 38 400
N
ET
-
N
ET
+
S N
ET
-
N
ET
+
S N
ET
-
N
ET
+
S N
ET
-
N
ET
+
S
Data Bus Shield
Connect to the ‘S’
terminal
RS-485
-
+ S
ECLYPSE
Figure 130: Setting the Baud rate on two Controllers on a Modbus RTU Data Bus Segment for Failover Protection
Set the Modbus network communication parameters with EC- gfx Program in the Resources Configura-
tion window, Modbus Device block.
Figure 131: Setting the Modbus Network Communication Parameters in EC-gfxProgram’s Resources Configura-
tion Window
See the EC- gfx Program User Guide for more information.
Data Bus Physical Specifications and Cable
Requirements
Cables composed of stranded conductors are preferred over solid conductors as stranded conductor
cable better resist breakage during pulling operations. Distech Controls strongly recommends that the
following data bus segment cable specifications be respected.
Parameter Details
Media Twisted pair, 24 AWG.
Shielding Foil or braided shield
Shield grounding
The shield on each segment is connected to the electrical system ground at one point
only; see
Data Bus Shield Grounding Requirements .
Characteristic impedance 100-130 Ohms. The ideal is 100-120 Ohms
Distributed capacitance between
conductors Less than 100 pF per meter (30 pF per foot). The ideal is less than 60 pF per meter (18pF
per foot)
Distributed capacitance between
conductors and shield
Less than 200 pF per meter (60 pF per foot)
Maximum length per segment 1220 meters (4000 feet)
Data Rate 9600, 19 200, 38 400, and 76 800 baud
Polarity Polarity sensitive
Multi-drop Daisy-chain (no T-connections)
EOL terminations 120 ohms at each end of each segment
Data bus bias resistors
When VCC=5V: 510 ohms per wire (max. of two sets per segment)
When VCC=3.3V (The APEX is 3.3V internal): 330 ohms per wire
Table 29: Modbus RTU Data Bus Segment Physical Specifications and Cable Requirements
Modbus RTU Communication Data Bus Fundamentals