ABB Industrial IT enabled REX 521 - Isolated RS-485 connection on the rear panel; Front panel optical connection for a PC; The service pin located on the rear panel; SPA bus

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Technical Reference Manual, General
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27
must be set manually through the HMI or the Relay Setting Tool
(Main menu\Configuration\Communication\Rear port). For rear
port options, refer to Table 4.1.12.2-1.
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The RS-485 port is used for connecting the unit to the communication bus by using
twisted pair cable. When the shielded twisted pair cable is used (recommended), the
shield can be connected to the earthing connector which is located on the rear panel
(refer to “Terminal connections” on page 45).
The communication port can be used with two different protocols: SPA and
Modbus. The user must set the selected protocol manually by using the HMI or the
Relay Setting Tool (Main menu\Configuration\Communication\Rear
port). For options, refer to the table Table 4.1.12.2-1.
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The front connector is standardized for ABB relay products and requires an opto-
cable (ABB art. No 1MKC950001-1).
The connector supports only the SPA bus protocol, and is connected to the RS-232
port of a standard PC. By using an optical connector, the PC is isolated galvanically
from the protection relay and disturbances are minimized.
Parameters for the serial communication, SPA address, Baud rate and
Slave status, can be changed manually in the HMI.
To ensure fluent communication flow, it is recommended to use 9.6 kbps baud rate.
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The service pin located above the connector X3.2 is used only in systems
communicating over the LON bus. The service pin is used during the installation
process or in fault detection. When the service pin is pressed, the neuron_id is sent
to the LON bus.
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The SPA bus protocol uses an asynchronous serial communication protocol (1 start
bit, 7 data bits + even parity, 1 stop bit). Adjustable parameters are Baud rate
(default 9,6 kbps) and SPA address (slave number). The communication
parameters for the front and the rear communication ports can be set individually.
The SPA bus protocol is sending events using event mask 1 (“V101” parameter of
each function block). The SPA event buffer stores the first 50 events.
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SPA optical
LON optical
IEC_103 optical
Modbus optical
SPA-485 RS-485
Modbus-485 RS-485