With the advent of PCI Express, the venerable PC platform marches forward. With Agilent Technologies, Microsoft, and Hewlett-Packard spearheading the thrust, PCI Express is amplifying and extending the utility of the venerable PC platform for leading-edge applications.
PCI Express's point-to-point serial topology kicks PCI up a few notches by providing scalable bus bandwidth, yet its layered packetized model maintains backward compatibility with existing PCI applications at the operating system level, including Windows.
The Bandwidth Quest
The name of the game, of course, is bandwidth. Leapfrogging PCI's parallel bus 132-Mbyte/s capability, serial PCI Express provides bandwidth capable of supporting Gbyte/s transfers. It does that by transferring packetized data in pairs of transmit-channel and receive-channel serial lines called lanes.
Lanes are aggregated into a parallel configuration of serial paths that can provide 250-Mbyte/s of bandwidth in each direction. A 16-lane-wide PCI Express configuration, called an x16, can support 4-Gbytes/s of bandwidth.
For users of pre-designed board-level products, PCI Express is delivering sparkling performance.
For example, look at American ELTEC's latest video frame grabber board. Dubbed the PC_EYE/ASYNC, it supports four simultaneous asynchronous video input channels, a feat in part possible due to the board's PCI Express bus interface.
The PC_EYE/ASYNC frame grabber can supplant up to four monochrome frame grabber boards for the acquisition of four independent and non-synchronized camera signals. In industrial imaging, digitization often commences immediately after an external trigger signal. These applications also re-set and re-start cameras so that more images can be grabbed in quick succession.
Single-Lane PCI Express
Not only does American ELTEC's board have an operating mode for four cameras, but the board's quad-A/D video-input module supports simultaneous digitization of the four camera signals. Data is stored in memory as four separate monochrome images in 8 bit-per-pixel formats. That data is then transmitted using a single-lane PCI Express interface with that provides double the data rate of the predecessor 32-bit parallel PCI bus interface.
In American ELTEC's hardware, the PCI Express single-lane interface operates as fast as 250-Mbytes/s, in full duplex. What's more, thanks to PCI Express's point-to-point connections, each of multiple PCI Express cards can use full system bandwidth. Each frame grabber packs a DRAM-based FIFO comprised of SO-DIMM (small outline dual in-line memory modules) plug-ins populated with DDR (double data rate) chips. This provides as much as 256-Mbytes of memory. That buffering ensures that no image data is lost, even if the PCI Express bus isn't available for more than a second.
Board-level instrument maker National Instruments (NI) is also using PCI Express in a frame grabber that can capture 1,000 frames a second. That's fast enough to capture a speeding bullet in flight as it hits, and passes through, an object.
Camera Link Matures
A few years ago NI worked with leading camera and frame grabber manufacturers to simplify connectivity between digital cameras and PCs. A resulting Camera Link standard specified data rates up to 680-Mbytes/s. At the time no method was widely available for acquiring images at that speed. If you wanted high-speed image-acquisition you were forced to use specialized cameras, stream data to banks of expensive on-board memory, or rely on stopgap PC bus technologies such as PCI 66/64 or PXI-X.
Now, by leveraging the capabilities of PCI Express, NI's $2500 PCIe-1429 image acquisition board can acquire high-speed data indefinitely on a PC, at the highest speeds, resolutions, and bit depths available for Camera Link cameras. That supports applications such as synchronized data-acquisition/image acquisition, fault analysis, and motion tracking.
Thanks to the board's four-lane PCI Express interface, images are acquired at full Camera Link bandwidth. In addition, you can sync other data acquisition measurements with each acquired image to analyze activities frame by frame in data-intensive applications (such as automotive crash tests).
You can use that speed for fault analysis by setting up a stop trigger to record images before and after an event on the factory floor. Or you could use high-speed imaging to perform particle image velocimetry, or track movement intricacies in gait analysis. Medical applications could measure the stimulus response of eye corneas to light, or analyze heart valve behavior under pathologic cardiovascular conditions.
PCI Express And GPIB
NI also has an IEEE-488/GPIB (General Purpose Interface Bus) controller for PCI Express. Priced at less than $500, NI's Model PCIe-GPIB plug-in lets you control GPIB instruments through PCI Express.
Thanks to NI's proprietary TNT IEEE-488.2 ASIC, the board can sustain transfer rates of more than 1.5-Mbytes/s using the IEEE-488.1 three-wire interlocked handshake. The system also implements IEEE-488.1's non-interlocked HS488 handshake for benchmarked data transfers of more than 7.9-Mbytes/s.
Another company leveraging PCI Express is Matrox Graphics. Its low-profile plug-in card, called the Millennium P650 LP PCIe 64, is priced at less than $250. Equipped with a PCI Express x16 (sixteen lane) port, it packs 64-Mbytes of graphics memory.
Using the company's proprietary DualHead technology, the Millennium P650 LP PCIe 64 lets you use two digital or analog monitors at a time, operating in either independently or in a stretched linked mode. Maximum resolution per display is 1920 x 1200-pixels for digital monitors, using one or two monitors. For two analog monitors resolution is 1920 x 1440-pixels. One analog monitor can show 2048 x 1536-pixels.
Just as PCI Express's wide bandwidth impacts video and graphics applications, data acquisition products are also leveraging the protocol. A new board called the Quixilica Venus VXS-1 from TEK Microsystems is a 6U-sized VME bus product combining high channel-count data-acq and tightly-coupled FPGA resources. It can sharply reduce board count and cost for front-end signal processing designs.
Typical uses are in electronic warfare systems, signals intelligence systems, and radar, where the board can serve as a modular open-standard building block. The Quixilica board's five data converter channels are based on Analog Devices's latest 14-bit 105-Msample/s AD6645 chips.
The VXS-1 is based on the VXS standard. VXS adds a switched serial interconnect to the venerable VMEbus, working with VMEbus's existing parallel bus architecture. Significantly, VXS supports PCI Express (as well as other standard open switched-fabric interconnects such as Infiniband, Serial RapidIO 4X, and 10-Gbit Ethernet). In the case of the VXS-1, PCI Express can communicate across a VME backplane.
In VXS, an individual transaction can have up to fifty times the bandwidth that it would have on VME64's parallel bus. Also, aggregate bandwidth in a chassis can be as much as nine hundred times the aggregate bandwidth available on the VME64 parallel bus. This bandwidth is delivered in a low-latency environment; an individual switch in VXS can pass traffic with latency as low as 150-ns.
VXS adds a high-speed connector to VME boards to support the switched fabric interconnects, with data rates up to 2.5-Gbytes/s for each 6U payload slot. For the Quixilica VXS-1, the VXS architecture provides the bandwidth and scalability to build systems ranging from single-card systems to 80-channel array processors.
Like Tek Micro's VXS-compatible board, an ultra-fast A/D board from Pentek can be fitted with an optional VXS interface. Pentek's Model 6826 VME A/D converter card provides two 4x full-duplex VITA-41 links, each capable of peak rates of 1.25-Gbytes/s. These links support PCI Express, as well as other Gigabit fabrics such as Xilinx Aurora and Serial RapidIO.
The $16,000 Model 6826 handles single-channel or dual-channel data acquisition at 2-Gsamples/s rates, with 10-bit resolution, thanks to the use of one or two Atmel AT84AS008 A/D converter chips. These very new A/Ds let the Pentek board directly digitize signal bandwidths up to nearly 900-MHz. With that, you can capture wideband radar and communication signals as a single channel instead of digitizing several smaller bandwidth slices.
The 6826 board's 10-bit RF converters are driven either in single-ended or differential mode, with RF applied through front-panel 50-ohm coax connectors. A transformer-coupled input works to 1-GHz, but a higher frequency input is also available as an option.
For More Information
American ELTEC, Inc., Quail Park IV, Suite 57, 2810 W. Charleston Ave., Las Vegas, NV 89102. Phone: 702-878-4085. Fax: 702-878-4735.
American ELTEC, 702-878-4085, www.americaneltec.com
Matrox Graphics Inc., 1055 St. Regis Blvd., Dorval, Quebec, Canada H9P 2T4. Phone: 800-361-1408, or (514) 822-6000. Fax: (514) 822-6363. E-mail: firstname.lastname@example.org
Matrox Graphics, 800-361-1408 or (514) 822-6000, www.shopmatrox.com
National Instruments Corp., 11500 No. Mopac Expwy., Austin, Texas 78759-3504. Phone: (512) 683-0100. Fax: (512) 683-8411. E-mail: email@example.com
National Instruments, 512-683-0100, www.ni.com
Pentek, Inc., One Park Way, Upper Saddle River, NJ 07458-2311. Call him at 201-818-5900, Ext. 229. Fax: 201-818-5904.
Pentek, 201-818-5900, www.pentek.com
TEK Microsystems, Inc., 2 Elizabeth Drive, Chelmsford, Mass. 01824-4112. Phone: 978-244-9200. Fax: 978-244-1078. E-mail: Sales: firstname.lastname@example.org, Information: email@example.com
TEK Microsystems, 978-244-9200, www.tekmicro.com