Element
Section 10: Edge SC Controller Operation
L-OMM-0003_A
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10.5.1 Communication Specification
Communication Protocol Modbus over RS485
Physical Layer
RS485 Two-Wire plus Signal Ground
Baud Rate
2400, 9600, 19200, 57.6k, 115k) (default 19200 bps)
Recommended Cable
18 AWG Shielded Twisted-Pair (STP)
Transmission Mode
RTU or ACSII (default RTU)
Maximum Cable Length
Without terminating resistors
- 115,000 baud --> 177 m (580 ft)
- 57,600 baud --> 353 m (1,158 ft)
- 19,200 baud --> 1,000 m (3,280 ft)
- 9,600 baud --> 1,000 m (3,280 ft)
- 2,400 baud --> 1,000 m (3,280 ft)
With 2 x 120 Ohm resistors
- 115,000 baud --> 1,000 m (3,280 ft)
- 57,600 baud --> 1,000 m (3,280 ft)
- 19,200 baud --> 1,000 m (3,280 ft)
- 9,600 baud --> 1,000 m (3,280 ft)
- 2,400 baud --> 1,000 m (3,280 ft)
Start Bit
1 Bit
Data Length
8 Bits for RTU Mode
7 Bits for ACSII Mode
Parity
None (2 Stop Bits)
Even (1 Stop Bit)
Odd (1 Stop Bit)
(default Even)
Addressing
1 to 247 (default 1)
10.5.2 Troubleshooting
If there is no communication, check the following:
•
Check that the polarity on the Modbus + and - terminals is correct
•
Check that the Modbus GDN terminal is securely connected.
•
Check that the Baud Rate on both devices is the same.
If the communication is intermittent, check the following:
•
Check that the communication cable is twisted pair type.
•
Reliable communication depends on the cable length & Baud Rate used. Long cable
length may require a lower baud rate.
10.5.3 Modbus Points List
The Modbus communication point list is stated below:
