Foxboro FBM237 P0914XS Serial Communication Module

Technical Specifications:

• Part Number: P0914XS
• Communication Ports: 2 ports — configurable as RS-232, RS-422, or RS-485
• Baud Rate Range: 300 bps to 115,200 bps (configurable per port)
• Data Bits: 7 or 8 bits
• Parity: None, Even, Odd
• Stop Bits: 1 or 2 bits
• Supported Protocols:
  • Modbus RTU (Master and Slave)
  • Modbus ASCII (Master and Slave)
  • Allen-Bradley DF1 (Slave)
  • Foxboro SCIM protocol
  • Custom ASCII/Binary protocols
• Maximum Cable Length: 1,200 meters (4,000 feet) at 9,600 bps (RS-485)
• Isolation: 1,500 VDC galvanic isolation on each port
• Operating Temperature: 0°C to 60°C (32°F to 140°F)

Functional Features:

• Dual independent serial ports — each port can run a different protocol simultaneously
• Master/Slave configuration — supports both polling and response modes
• Buffered communication — 4 KB transmit and receive FIFO buffers per port prevent data loss under high traffic
• Diagnostic LEDs — TX, RX, and ERROR status indicators on front panel
• Online configuration — baud rate, protocol, and addressing can be changed without processor cycle interruption

Performance Parameters:

• Maximum Simultaneous Connections: 32 devices per port (Modbus RTU)
• Transaction Response Time: Less than 10 ms at 115,200 bps
• Data Throughput: Up to 115,200 bps per port
• ESD Protection: ±15 kV air discharge, ±8 kV contact discharge (IEC 61000-4-2)

Structural Characteristics:

• Form Factor: Standard Eurocard module (160 mm × 233 mm)
• Mounting: Horizontal rack mount in I/A Series chassis
• Connectors: Dual DB-9 (RS-232) or screw-terminal (RS-485) on front panel; dual backplane connectors
• Weight: Approximately 0.5 kg (1.1 lbs)

Working Principle:
The FBM237 receives serial data from external devices via its RS-232/RS-485 ports. Data is framed according to the configured protocol (Modbus, DF1, etc.), placed in the receive FIFO buffer, and transferred to the FBM219 control processor via the backplane during the next scan cycle. Outbound data from the processor is placed in the transmit FIFO and sent to the target device on the configured port. The module handles all protocol framing, CRC checking, and timing — the processor only deals with parsed data values.

Advantages & Highlights:

• Dual-port design enables simultaneous communication with two different networks
• Wide protocol support — eliminates need for protocol converters
• 1,500 VDC isolation protects the DCS from ground loops and surge damage
• Part number P0914XS is a field-proven revision with extended temperature range

Applicable Industries:

• Oil and Gas (SCADA integration, RTU communication)
• Water and Wastewater (remote station communication)
• Power Generation (VFD control, relay communication)
• Manufacturing (PLC-to-DCS data exchange)

Installation Requirements:

• Install in any available chassis slot adjacent to or near the FBM219 processor for optimal scan performance
• Use shielded twisted-pair cable for RS-485 connections — maximum length 1,200 meters
• Terminate RS-485 bus with 120-ohm resistor at both ends
• Ensure common ground reference is established for RS-232 connections

Usage Precautions:

• Do not exceed 115,200 bps — this is the maximum supported speed
• RS-485 requires proper termination — missing termination causes signal reflections and data errors
• Isolation rating is 1,500 VDC — do not connect to circuits exceeding this voltage
• Verify protocol settings match the external device before going live