The National Instruments AT-485/2 is a 2-port ISA serial interface card engineered for industrial and automation environments requiring multi-protocol serial communication. Each port independently supports RS-232, RS-422, or RS-485 standards, enabling flexible integration of legacy serial devices with ISA-based computer systems. The card delivers differential transmission line performance with extended cable reach, ±15 kV ESD protection, and hardware handshaking via RTS/CTS control lines.
Technical Specifications
Serial Configuration & Performance
• 2 independent ports, each supporting RS-232, RS-422, and RS-485 protocols
• 16550 UART type with 16-byte transmit/receiver FIFO buffer
• Up to 31 devices per port on RS-485 networks
• Maximum cable length: 4,000 ft (1.2 km) for RS-485 without surge limitation
• Standard baud rates supported up to 2000 kbaud
• RTS/CTS hardware handshaking
Protection & Termination
• ±15 kV ESD protection on data lines for RS-485 and RS-232
• Configurable bias voltage and termination per port to eliminate transmission line ringing
• DB-9 male connectors for all ports
Electrical & Environmental
• External power supply: 9 V to 30 V
• Operating temperature: 0 to 70 °C
• Storage temperature: -40 to 85 °C
• Maximum working altitude: 2,000 m
• Humidity: 5 to 95% non-condensing (IEC-60068-2-56)
• Indoor use only
– Key Features
• Dual-port architecture for simultaneous multi-device connectivity
• Metal baseplate with hard-plastic case construction
• LED indicators for transmitter and receiver status monitoring
• Enhanced serial drivers for improved performance and interrupt sharing
• Meets EN 61326 and CISPR 11 Class A emissions and immunity standards
– Typical Applications
RS-485 multi-drop networks in industrial control; RS-232/422 device integration in legacy automation systems; point-to-point and networked sensor/actuator communication; extended-distance serial telemetry over differential lines.
– Compatibility & Integration
Functions as standard COM ports compatible with serial communication applications. Supports Windows 2000 and Windows 9x operating systems on ISA bus architecture.
