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PC/104 extenders link I/O across noise-free optical waveguides

Posted: 30 May 2005 ?? ?Print Version ?Bookmark and Share

Keywords:fpga? hardent canada? optical pc/104? isa-bus? extender?

Here's a unique FPGA-based product from a small company called Hardent Canada that should find a home in electrically noisy environments, such as industrial data acquisition systems. Hardent's Optical PC/104 ISA-bus eXtender, or OPIX, is a small board runs eight simultaneous A/D channels" target=_blank>plug-in board that lets you extend the range of any PC/104-based data-acq/control system. It does that by means of a multi-mode fiber optic pair operating at a 1,310nm wavelength.

In most PC/104 stacks, the processor card uses the standard PC/104 connector to communicate with any I/O cards in a system. Typically, the standard ISA bus protocol is used, too.

I/O is usually connected to any sensors or peripherals in a system by means of copper cabling. That makes the system susceptible to noise, RF, voltage drops, ESD (electrostatic discharge), and differences in ground reference points.

Let's get closer
With noise susceptibility and IR drops as great as they can be, it's often desirable to locate a PC/104 unit closer to its I/O. That's where the OPIX comes in. Distance is no longer a constraint.

In operation, the OPIX acts as an optical PC/104-to-PC/104 bridge. The distance between two cards can be up to 2km in length, and the use of a fiber optic link provides complete electrical isolation, eliminating any problems related to differences of reference voltages. An optional long-range module can increase the maximum range of an OPIX link to 50km.

Plugging directly onto PC/104 modules (CPU, I/O, or any other type), the board operates transparently; there's no need to install software or modify your existing set-up. The card is fitted with standard ST optical connectors, and Agilent Technologies optical transceivers.

Internally, a Xilinx FPGA implements multiple state machines to handle bus control, and a SERDES (serializer-de-serializer). All ISA I/O bus transactions are supported, including I/O reads (8-bit and 16-bit access), I/O writes (8-bits and 16-bits), interrupt requests, and I/O channel checks.

What's more, a single OPIX pair can support a mix of 8-bit and 16-bit cards at the remote location. A proprietary patent-pending protocol provides continuous link-failure for both sides of a path.

Non-PC/104 applications
Where the OPIX cards aren't at the same site, multiple OPIX cards can be used to create a star topology. The possibilities are constrained only by the underlying limitations of the ISA bus.

For non-PC/104 applications, bus adapter cards are available. These include PC/104-to-ISA, PC/104-to-PCI, and PC/104-to-CompactPCI. In conjunction with an OPIX pair, they can be used to connect a remote PC/104 stack to a PCI-based or CompactPCI-based system.

Eval kit available
An evaluation kit is also available. It includes: two OPIX cards, a pair of 10-m-long optical fibers, a card extractor, a programming cable, and address configuration software.

-Alex Mendelsohn

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