National Instruments PCI-485-2

The National Instruments PCI-485/2 is a dual-port serial communication card designed for PCI-Bus PCs, offering robust connectivity for industrial applications. Measuring 6.5 inches (165 mm) in length, this card is compatible with 5V PCI, 3.3V PCI, and PCI-Z slots. Each port supports both RS-485 differential and single-ended communication modes, with the capability to incorporate bias voltage, ensuring a reliable "zero" state when all transmitters are off. This feature is crucial for maintaining communication integrity, particularly in longer line setups where line termination is necessary to minimize signal reflections. The PCI-485/2 utilizes 16550 UARTs to facilitate asynchronous communication, boasting a 16-byte transmit and receive FIFO buffer that helps prevent data loss in multitasking environments while ensuring full compatibility with traditional IBM serial ports. Enhanced by a built-in crystal oscillator, this card achieves baud rates exceeding 115,200, with maximum speeds of up to 460,800 baud, adjustable via onboard jumpers. The TI 75ALS180 driver/receivers provide capability for long-distance communication without signal degradation, and they are equipped with thermal shutdown features to protect against communication disruptions. Although designated as obsolete by National Instruments, the PCI-485/2 remains available for purchase and repair through Apex Waves, ensuring continued support for legacy systems.