If there was any doubt that PCI Express will become the next interface of choice for high-speed imaging peripherals such as frame grabbers, graphics controllers, and I/O boards, it was dispelled at the recent Intel Developer Forum (February 2004). There, PLX Technology (Sunnyvale, CA, USA; www.plxtech.com) demonstrated real-time digital image transfers over PCI Express using its latest-generation PCI-to-PCI Express bridge (P-Bridge) emulator designed to allow PCI 64-based designs to interface to the new PCI Express standard.
The company used a NetCam camera from StarDot Technologies (Buena Park, CA, USA; www.stardot-tech.com), which contains a Motorola Cold-Fire processor running Linux. The camera periodically takes images and saves them as JPEG image files. It also contains a Web server that can display the JPEGs through a Web browser. With its on-board processing capability, the camera can dial an Internet service provider by attaching a modem to its serial port.
To show PCI 64-to-PCI Express bridging technology, PLX Technology demonstrated an imaging system that captures image data and transfers it over the PCI Express interface.
Flexibility in the camera's firmware allows it to attach directly to a UNIX-based PLX PCI 9656-based board through serial connection (and over the PCI Express serial forwarding system). The board, which uses a PowerPC-based processor, is part of the PLX PCI 9656 reference design kit (RDK) PLX ships as a tool to help designers developing boards and systems with the PCI 9656—a 64-bit, 66-MHz PCI controller. The PCI 9656 RDK board was connected to P-Bridge emulator over a PCI 64 bus. The P-Bridge emulator provided the bridge between the PCI 64 and PCI Express interface.
The PCI Express side of the P-Bridge was connected to a second P-Bridge emulator, which bridged PCI Express back to the PCI 64 interface standard. Using the PCI 64 bus, the system was interfaced to another PCI 9656 RDK board and then over a standard communications port to a Dell PC running UNIX. A program running on the two boards read each serial port and forwarded any data found to the serial port of the other board. Data were forwarded through the two P-Bridge cards and over the PCI Express link between them.
"With this accomplished, it appeared to the UNIX PC that it was connected directly to the camera, with the PCI Express diversion being totally transparent. Once the camera "dialed-in" to the UNIX machine and established a TCP/IP link, images could be viewed on a Web browser running on the Dell PC," says Chris Youman, a senior PLX Technology product-marketing manager.
By using bridge emulators, designers who have already developed imaging, graphics, and I/O peripherals based on the PCI 64 standard can easily migrate to PCI Express. While this will save design time and cost in implementing first-generation PCI Express-based boards, it is unlikely to be a panacea for future designs where even higher I/O speeds will be demanded. In such cases, designers will more than likely implement high-speed PCI Express interfaces directly on board-level products, overcoming the bandwidth limitations necessitated by such bridging solutions. To meet such demands, PLX Technology and other IC vendors will introduce a range of PCI Express interface ICs later this year.