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Gage digital capture card converts PC to logic analyzer

Posted: 18 Aug 2004 ?? ?Print Version ?Bookmark and Share

Keywords:fpga? gage applied technologies? compuscope? 3200c? compactpci/pxi logic analyzer?

Equipped with an onboard FPGA, Gage Applied Technologies' plug-and-play CompuScope 3200C looks like a pretty nifty plug-in. That's especially true when you consider its less-than-$6,000 price tag that includes PC software.

As a CompactPCI/PXI logic analyzer, it lets users capture up to 32 bits of CMOS/TTL-compatible or ECL-compatible data into its on-board memory at clock rates up to 100MHz. The 3200C will then give a 100MBps transfer rate to the computer's memory bus.

To configure an analyzer in a CompactPCI/PXI system, users will need at least one free 6U slot (for a basic 3200C equipped 2MB of memory), and a dedicated controller or a PC equipped with at least with 128MB of DRAM and 50MB of free hard disk space. The card will dissipate a hefty 26W, though, so it's likely that some forced air cooling will be needed too.

The system also relies on SVGA video, and is supported for Windows 95, Windows 98, Windows NT, Windows XP and Windows 2000.

The use of high-speed comparators with programmable thresholds at the system's front-end supports virtually any logic level. The product will readily accommodate conventional 5V TTL or CMOS logic, as well as newer 3.3V and 2.7V CMOS, as well as ECL, PECL and custom logic levels. To avoid ringing and reflections, all of the CompuScope 3200C's inputs are resistively terminated at 50 ohms.

Although the press release stated that users must choose between differential or single-ended signal inputs, let me emphasize that that's set at the factory; it's not something that you can change under software control.

Regardless of that constraint, a 3200C can be configured in software to look at data path widths of 8 bits, 16 bits or 32 bits, letting consumers maximize the use of memory for 8bit or 16bit inputs.

Expanding logic analysis

Not stated in the company's release notes is that multiple CompuScope 3200C boards can also be used in Master/Slave configurations. If one chooses to do that, they can accommodate input words of 64 bits, 96 bits or even 128 bits.

For CMOS/TTL signal sources that ca not drive the analyzer's 50-ohm inputs, Gage can supply a buffer board that buffers data with 50-ohm line drivers. The output of the buffer board connects to the 3200C using a 6ft ( pleated foil cable.

The input to the buffer board is a 68-pin insulation displacement connector (for the data) and a BNC coax connector for trigger signals. Another BNC handles a clock input. Users can choose either an internal or external clock, and select them by software. When the internal clock is selected, sampling is based on a crystal-controlled oscillator to ensure short term and long-term accuracy.

As mentioned, the 3200C also packs an FPGA. The output of the comparators is fed into the FPGA for de-muxing the data from 8, 16 or 32 bits to a 64-bit width. The FPGA also lets users to build up their own customized digital acquisition system.

Gage's press notes refer to the board's 2MB of memory. It's in the form of SRAM, for speed. Moreover, the memory array is configured as a circular buffer. With that, it's possible to store both pre-trigger and post-trigger data, so that you can inspect what happened before and after a trigger event.

The standard-sized memory array provides for storage of 2Mwords when an input is 8 bits wide, or a half million samples with a 32bit-wide word. However, you can set up a system with more boards for more memory.

Software support

A word about software support. As the press release notes, the CompuScope 3200C comes with Gage's GageBit data capture software for Windows. Freeing users from programming, the GageBit lets a 3200C operate in all available operating modes, with captured digital samples displayed graphically with each bit plotted as a function of time. Using GageBit, samples can also be displayed as decimal, hex or binary. Data can also be logically manipulated and stored to a file.

The company's SDKs (software development kits) let users work in C and C++, or use the MatLab, LabVIEW or LabWindows/CVI graphical environments. The CompuScope SDKs also include digital input sample programs to get buyers started.

- Alex Mendelsohn

eeProductCenter





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