NI Serial Hardware and Software


The ENET serial hardware gives you a variety of solutions for serial communication. The RS-232 interfaces work with the RS-232 protocols. The RS-485 interfaces work with the RS-422 and RS-485 protocols. You can use the RS-232 ports for serial communication up to distances of 50 ft. You can connect the RS-485 ports to up to 31 devices using serial cable lengths up to 4,000 ft.

The RS-232 ports are DTE. In the RS-232 specification, Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) refer to the types of equipment on either end of a serial connection. In general, DTE and DCE refer to computer equipment and modems, respectively. For more information about cabling a RS-232 port to other devices, refer to RS-232 DTE vs. DCE.

The RS-485 boards support four hardware transceiver control modes for reliable communication with two and four-wire devices. For more information about transceiver control modes, refer to RS-485 Transceiver Control.

All serial ENET interfaces contain FIFO (First-In-First-Out) buffers to reduce susceptibility to interrupt latency for faster transmission rates. Also, serial ENET interfaces contain additional onboard buffers to reduce susceptibility to Ethernet network traffic.

With a serial ENET interface, you gain all the features inherent in a networked device: fewer cabling distance restrictions, device sharing, and communication with devices throughout the Internet. In a serial application, you usually are restricted to the distance limitations of the RS-232, RS-422, or RS-485 specifications. Because the serial ENET interface uses Ethernet, you can add an unlimited distance to your application by exploiting the distances available using a networked device. Device sharing with a serial ENET interface happens on a per-port basis. That is, although the serial ENET interface supports network connections from multiple hosts, each serial port is associated with only one host at a time.

Dynamic Host Configuration Protocol (DHCP) is available on many networks to configure network parameters automatically. DHCP simplifies the installation and configuration process for the serial ENET. For more information about DHCP, refer to Using DHCP.

If your network does not support DHCP, use the NI Ethernet Device Configuration utility as described in Serial ENET Configuration to configure network parameters for the serial ENET interface.