1MRS 751108-MUM
REX 521
33
Protection Relay
Technical Reference Manual, General
4.1.12.3. Front panel optical connection for a PC
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.
4.1.12.4. The service pin located on the rear panel
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.
4.1.12.5. SPA bus
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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