Bristol FB300 DNP3 Configuration for SCADA Communication
Key Takeaway
How to configure DNP3 outstation parameters on the Bristol FB300 for communication with SCADA masters — covering address assignment, data link settings, point-to-index mapping, event classes, unsolicited responses, and serial/TCP transport options.
Quick Answer
The Bristol FB300 operates as a DNP3 Level 2 outstation, responding to polls from a SCADA master. Configuration involves assigning a unique DNP3 address, mapping internal points to DNP3 data object indexes, setting event classes and reporting behavior, and choosing between serial (RS-232/RS-485) or TCP/IP transport.
DNP3 Protocol Fundamentals
DNP3 (Distributed Network Protocol version 3) is the dominant SCADA communication protocol in North American oil and gas, water/wastewater, and electric utility industries. Understanding these core concepts is essential for FB300 configuration:
- Master/Outstation model: The SCADA master initiates communication by sending requests (polls) to outstations. The FB300 operates as an outstation, responding with requested data.
- Data objects: DNP3 organizes data into typed objects — Binary Input, Analog Input, Binary Output, Analog Output, Counter — each identified by an index number.
- Event classes: Changes in point values generate "events" that can be assigned to Class 1, 2, or 3. The master can poll for specific classes, allowing priority-based data retrieval.
- Unsolicited responses: The outstation can proactively send data to the master without waiting for a poll — useful for critical alarms and fast-changing values.
Step 1 — DNP3 Address Assignment
- Assign a unique DNP3 outstation address (0–65519). Each FB300 on the communication network must have a different address. Maintain an address registry spreadsheet to prevent conflicts.
- Record the master address that will poll this outstation. If multiple masters will poll the same FB300 (e.g., primary and backup SCADA), configure the appropriate master addresses.
Step 2 — Data Link Layer Configuration
- Set the data link layer timeout — how long the FB300 waits for a complete frame before discarding. Typical values: 1–5 seconds for serial, 1–2 seconds for TCP.
- Set the application layer timeout for multi-fragment responses. This must be long enough for the master to receive all fragments of a large response (e.g., an integrity poll returning hundreds of points).
- Enable or disable data link layer confirmation — this adds reliability on noisy serial links but increases bandwidth usage.
Step 3 — Point-to-DNP3 Index Mapping
This is the most critical and error-prone step. Every FB300 internal point that should be visible to the SCADA master must be mapped to a DNP3 data object with a specific index:
| FB300 Point | DNP3 Object Type | DNP3 Index | Description |
|---|---|---|---|
| TK101_LVL | Analog Input | 0 | Tank 101 level (feet) |
| TK101_PRESS | Analog Input | 1 | Tank 101 pressure (PSI) |
| PMP201_RUN | Binary Input | 0 | Pump 201 running status |
| PMP201_START | Binary Output (CROB) | 0 | Pump 201 start command |
| FLW301_TOTAL | Counter | 0 | Flow meter 301 accumulated volume |
Maintain a master DNP3 point map document that matches the SCADA master's database configuration. Mismatched index numbers are the number-one cause of "data showing up on the wrong point" issues.
Step 4 — Event Class Assignment
- Assign critical alarms and safety shutdown status to Class 1 — the master polls Class 1 most frequently.
- Assign process variables (levels, pressures, temperatures) to Class 2 — polled at normal intervals.
- Assign non-critical status and diagnostic points to Class 3 — polled less frequently to conserve bandwidth.
- Configure event deadbands for analog inputs — this determines how much the value must change before generating a new event. Too small a deadband floods the event buffer; too large misses meaningful changes.
Step 5 — Unsolicited Response Configuration
Unsolicited responses allow the FB300 to push critical data to the master immediately, without waiting for the next poll cycle:
- Enable unsolicited responses and specify which event classes trigger them (typically Class 1 only).
- Configure the unsolicited retry count and retry delay — if the master doesn't acknowledge the unsolicited response, the FB300 will retry.
- Set the hold time after startup — this delays unsolicited responses after a power cycle to give the master time to perform an integrity poll and establish baseline data.
Step 6 — Transport Selection
Serial (RS-232 / RS-485)
- Configure baud rate (9600, 19200, or 38400 are common for DNP3 serial), parity, and stop bits.
- For RS-485 multi-drop networks, enable RTS/CTS flow control to manage bus contention.
- Set the inter-character timeout to match the communication link characteristics.
TCP/IP
- Assign the FB300 a static IP address on the SCADA network.
- Configure the DNP3 TCP listening port (default: 20000).
- If using cellular or satellite links, configure TCP keep-alive intervals to detect connection drops.
Frequently Asked Questions
The Bristol FB300 supports DNP3 Level 2 outstation functionality, which includes static and event data reporting for binary inputs, analog inputs, binary outputs, analog outputs, and counters. This makes it compatible with virtually every modern SCADA master platform.
In OpenBSI, each internal point that should be visible to the SCADA master is assigned a DNP3 data object type (Analog Input, Binary Input, Binary Output, Counter) and a unique index number. Maintain a master point map document that matches both the FB300 configuration and the SCADA master's database to prevent index mismatch errors.
The default DNP3 TCP listening port is 20000. This can be changed in the FB300 communication configuration if your network requires a different port. Ensure the SCADA master's DNP3 driver is configured to connect to the same port.
DNP3 event classes (1, 2, 3) prioritize data reporting. Assign critical alarms to Class 1 (polled most frequently), process variables to Class 2 (normal polling), and non-critical diagnostics to Class 3 (polled least frequently). Configure analog event deadbands to control how much a value must change before generating a new event.