Product Overview
Two-Port RS-485 and RS-422 Serial Interface for PXI Chassis
Condition
Used and in good cosmetic shape; shows signs of normal use, including scuffs, scratches, and minor wear. The photos show this exact module. The silver front panel is printed NI PXI-8421 RS-485 Serial with PORT 1 and PORT 2 male DB-9 connectors, both with intact jackscrew standoffs and clean gold contacts. The black PXI ejector handle and captive panel screw are both present. The component side carries the National Instruments logo with a 1998 copyright line, a CE mark, a MADE IN HUNGARY label, an assembly label reading 185410D-02, and a barcode label reading 11FE7C6. The solder side is silkscreened 185412A-01 with MADE IN THE U.S.A. and UL 94V-0, so the bare board was fabricated in the U.S. and the module was assembled in Hungary. Solder joints are bright, the ERNI 2mm hard-metric backplane connectors are female receptacles whose housings and blue keying insert look intact in the photos, and no burn marks, corrosion, rework, or missing components are visible in any view.
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Product Overview
The National Instruments PXI-8421 is a 3U PXI serial interface module that puts RS-485 and RS-422 ports into a PXI chassis. The PXI-8421 was built in several port configurations, and the front panel on this one settles which: it is the two-port DB-9 version, marked PORT 1 and PORT 2. Each port runs RS-485 or RS-422 with selectable 2-wire or full duplex control, handles baud rates up to 460.8 kbit/s, and is buffered by 64-byte transmit and receive FIFOs. There is no port-to-port isolation; the ports share a common ground. Under the NI-Serial and NI-VISA drivers the module comes up as standard Windows COM ports, so LabVIEW, LabWindows/CVI, and ordinary serial code address it the same way they address a motherboard port. Board-level markings back up the identity: assembly 185410D-02 on the component side, bare board 185412A-01 on the solder side, and an AMCC PCI MatchMaker S5920Q bridge doing the PCI translation behind the front panel.
Key Features
- Configuration on this unit: 2-port male DB-9, confirmed by the PORT 1 and PORT 2 markings on the front panel
- Interface: RS-485 / RS-422 with selectable 2-wire or full duplex control
- Maximum baud rate: 460.8 kbit/s
- Buffering: 64-byte transmit and receive FIFOs
- Isolation: none port to port; common ground across ports
- Form factor: PXI 3U, approximately 3.94 in x 6.37 in
- Supports hardware flow control, loopback, and multi-drop communication
- Plug and play with the NI-Serial and NI-VISA drivers; presents as standard Windows COM ports
- Board markings: assembly 185410D-02, bare board 185412A-01, barcode 11FE7C6, National Instruments copyright 1998, CE marked
- Family note: the PXI-8421 was also produced in 4-port 10P10C and 8-port SCSI versions; this listing is the 2-port DB-9
Applications
- Test engineer rebuilding a PXI rack that needs two RS-485 legs back in the chassis without giving up a slot to a USB adapter hanging off the bench
- Automation technician talking to multi-drop RS-485 field devices, drives, or meters from a LabVIEW sequence instead of a laptop and a dongle
- Lab maintaining an older LabWindows/CVI test station where the original serial module failed and the test program expects COM ports at the same addresses
- Integrator bringing legacy RS-422 instruments into an automated test setup that already runs on PXI
Frequently Asked Questions
Which port configuration is this one?
Two ports, male DB-9, one per RS-485 or RS-422 line. The front panel photo shows the PORT 1 and PORT 2 legends directly, so there is no guessing between this and the 4-port 10P10C or 8-port SCSI versions of the PXI-8421.
Will it work with LabVIEW and my PXI chassis?
The module is a standard 3U PXI card and is driven by NI-Serial and NI-VISA, which expose it as ordinary Windows COM ports for LabVIEW, LabWindows/CVI, or any serial code. Driver version support for a specific Windows release and chassis controller is not confirmed here, so check the NI documentation for your controller and operating system before you commit to it.
Are the two ports isolated from each other?
No. The PXI-8421 has no port-to-port isolation and the ports share a common ground. If your bus needs galvanic isolation between nodes, plan on external isolators.
What am I actually taking on with a used PXI module like this one?
You get the single module in the photos and nothing else: the 2-port DB-9 card with its front panel, ejector handle, and backplane connector, with no cables, no chassis, and no driver media. It is graded used and cosmetically good, and we do not publish a powered bench test with this listing, so the photos and that grade are the spec. Every view is here, front panel, component side, solder side, and backplane connector, so you can judge the connectors and the board yourself before you buy rather than bidding on a rack of unknown PXI cards and hoping the serial module in the middle of it is the version you need. This one clears our free-shipping line on its own, and orders leave the Idaho warehouse the same or next business day.
Copyright 1998 on the silkscreen, an AMCC PCI MatchMaker doing the translation, and two DB-9 ports that still speak the multi-drop dialect half the world's machinery was wired for. Slot it in and let the old talkers keep talking.
