B&R SG3 legacy PLC families—including 2005, 2003, and PowerPanel 15/35—often use the INA serial protocol for an Automation Studio online connection. Use the default parameters first, then probe the supported parameter combinations with Runtime Utility Center (RUC) when the project configuration is unknown.
Start with the INA default parameters
The default INA configuration is 57600 baud, 8 data bits, one stop bit, and even parity. These values apply only when the developer did not change the serial-interface parameters in the PLC project.
| Parameter | Default | RUC probe variants |
|---|---|---|
| Baud rate | 57600 | 115200, 57600, 38400, 19200 |
| Data bits | 8 | 8 |
| Stop bits | 1 | 1 |
| Parity | Even | Even, Odd, None |
Verify the serial cable wiring
INA does not use hardware handshaking. The cable requires only RX, TX, and GND, with the transmit and receive conductors crossed. For 9-pin D-SUB connectors, use this pin mapping:
Pin 2 -> Pin 3
Pin 3 -> Pin 2
Pin 5 -> Pin 5Confirm the wiring before interpreting failed parameter probes as a PLC configuration problem.
Probe unknown parameters with RUC
Runtime Utility Center is included with Automation Studio installations. A RUC instruction-list file with the .pil extension can automate attempts across the documented baud-rate and parity variants.
- Open the PIL instruction list in a text editor.
- Replace its configured COM port, such as
COM8, with the port assigned to the connected serial adapter. - Open and execute the PIL file in RUC.
- Allow RUC to test even, odd, and no parity at 115200, 57600, 38400, and 19200 baud, always with 8 data bits and one stop bit.
- Stop troubleshooting parameter selection when RUC reports that an online connection has been established.
Interpret the probe result
A successful popup identifies a working serial parameter set and ends execution. If execution ends with an error popup, the tested combinations did not establish an online connection.
A complete failure does not prove that the PLC is defective. The configured parameters may fall outside the tested combinations, the application may be using the serial interface to communicate with a third-party device, or the developer may have disabled serial online access. Review the PLC project configuration when available to distinguish these cases.
FAQ
What are the default B&R SG3 INA serial settings?
Use 57600 baud, 8 data bits, one stop bit, and even parity. These defaults will not work if the PLC project changed the interface configuration.
Which serial settings should RUC test for an SG3 PLC?
Test 115200, 57600, 38400, and 19200 baud with even, odd, and no parity. Keep the data format fixed at 8 data bits and one stop bit.
Why does an SG3 serial connection fail for every tested setting?
The correct parameters may not be in the probe list, the PLC application may have assigned the port to another serial function, or serial online access may be disabled. Also verify the crossed RX/TX wiring and common ground before reviewing the PLC project.