ABB TPU2000 Technical Manual page 372

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide
Figure 6 – Termination Using External Resistors And The Telebyte Converter Being An "In-Line"
Figure 7 - Termination Using External Resistors On The IED's And Using The Telebyte Converter
RS485 Biasing
Figures 4 through 7 illustrate the addition of resistors between the TX/RX (+) line and +V, and TX/RX (-) line and
ground. These resistors are called bias resistors. Bias resistors are inserted at one node only, preferably at one
extreme end of the network.
The TELEBYTE 245 is a "passive bias" unit in that when no device is communicating on the network, the data
lines float. With the addition of the Pull-Up and Pull –Down resistors, the line is biased when no device is driving
the lines. Biasing reduces the communication lines from being saturated with RFI or EMI induced noise from
being coupled on the line. Addition of biasing on the network reduces the induced noise on the line.
The typical utility installation is an electrically noisy environment. Addition of data line biasing is recommended.
RS485 Conductor Connectivity
The TELEBYTE unit uses the following pins for RS 485 communication:
PIN 2 - TX/RX (A) or TX/RX (-) or A
PIN 14- TX/RX (B) or TX/RX (+) or B
PIN 7 – GROUND
The TELEBYTE interface is a DB 25 FEMALE interface.
Topology Diagram for RS 485 Multi-drop Architecture - if external resistors are
installed providing proper termination. NOTE: Termination at end units.
Cable "A"
See Attached Diagrams
475 Ohms
120 475 Ohms
Ohms
55 56 57 58 59 60 61 -----
BANK SW 2
AUX Port
Dipswitch 1 = DOWN (Term Out)
Three-wire cable with
shield. Cable "B" - see attached diagram.
* - See note A
E C E C
Unit 1 Unit 2
Jumpers
End Unit Inline Unit
J6, J7, J8
"OUT"
32 Devices and 4000 Feet Maximum loading and distance.
Unit
Topology Diagram for RS 485 Multi-drop Architecture - if external resistors are
installed providing proper termination. NOTE: Termination at end units.
475 Ohms
120 475 Ohms
Ohms
Cable "A"
See Attached Diagrams
55 56 57 58 59 60 61 -----
AUX Port
Unit 3
Three-wire cable with
shield. Cable "B" - see attached diagram.
E C
* - See note A
E C E C
Unit 1 Unit 2
Jumpers
End Unit Inline Unit
J6, J7, J8
"OUT"
32 Devices and 4000 Feet Maximum loading and distance.
As An End Unit
* Note A - Following Cable Recommended
Alpha # 58902
Belden # 9729, # 9829
Carol #58902
120
Ohms
55 56 57 58 59 60 61 -----
AUX Port
E C E C
Unit 31 Unit 32
Inline Unit End Unit
* Note A - Following Cable Recommended
Alpha # 58902
Belden # 9729, # 9829
Carol #58902
BANK SW 2
Dipswitch 1 = UP (Term IN)
E C
Unit 31
Inline Unit End Unit
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