The NI 9870 is a 4-port RS232 serial interface module for CompactRIO systems, delivering direct FPGA access to four independent RS232 DTE ports. Each port operates up to 921.6 kbps with configurable data bits (5, 6, 7, 8), stop bits (1, 1.5, 2), and flow control (XON/OFF, RTS/CTS, None). The module integrates 64-byte UART FIFO buffers per port for optimized FPGA resource utilization and simplified firmware development. Connectors use RJ-50 receptacles with ±15 kV ESD protection on data lines. The module achieves 1.28 Mbps aggregate throughput and operates from 8 VDC to 28 VDC external power. Active mode consumes 0.5 W maximum; sleep mode draws 50 µW. Receive signals tolerate ±8 V continuous, while transmit signals deliver ±13.2 V typical. Cable capacitance limit is 250 pF equivalent. The module provides 1000 V_rms isolation overvoltage rating between port and earth ground, with MTBF of 448,008 hours at 25 °C under Bellcore Issue 6 stress analysis.
Technical Specifications
• Ports: 4 independent RS232 DTE, ANSI/EIA/TIA-232 compliant
• Connectors: RJ-50 receptacles
• Maximum Baud Rate: 921.6 kbps per port
• Aggregate Throughput: 1.28 Mbps
• UART FIFO Buffer: 64 bytes per port
• Data Bits: 5, 6, 7, 8
• Stop Bits: 1, 1.5, 2
• Flow Control: XON/OFF, RTS/CTS, None
• External Power: 8 VDC to 28 VDC
• Power Consumption: 0.5 W (active), 50 µW (sleep)
• Cable Capacitance Tolerance: Up to 250 pF equivalent
• ESD Protection: ±15 kV (Human Body Model)
• RXD/CTS/DSR/DCD/RI Maximum Continuous Voltage: ±8 V
• Transmit Signal Voltage (Typical): ±13.2 V
• Receive Signal Voltage (Typical): ±25 V
• Isolation Overvoltage: 1000 V_rms (port to earth ground)
• Measurement Category: CAT I
• MTBF: 448,008 hours at 25 °C
– Key Features
• Direct LabVIEW FPGA API access for custom timing and synchronization
• Per-port UART FIFO buffering reduces firmware complexity
• Dual voltage signaling supports legacy and modern serial devices
• Compact form factor integrates into distributed I/O chassis
– Typical Applications
• Industrial serial device integration in distributed embedded systems
• Multi-port serial data logging and instrument control
• Laboratory equipment interfacing requiring FPGA-level timing precision
– Compatibility & Integration
Module mounts directly in CompactRIO I/O slots. External power requires isolated 8–28 VDC supply via four-position pigtail. Cable runs must not exceed 30 m for specified EMC performance.
