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Adopting PCI Express® in Data Acquisition
Hank Lin, Product Manager, ADLINK Technology Inc.
This article examines the PCI Express® I/O interconnecting standard and its perceived benefits for data acquisition applications. The beginning of the article discusses the evolution of this standard, including its key specifications and features. It then discourses the potential benefits that PCI Express brings to data acquisition.
 What is PCI Express™?
PCI Express is a new industry-standard interconnect technology designed to provide high-bandwidth local I/O connectivity across desktop, mobile, and communication platforms. PCI Express adopts serial interconnects instead of the older parallel PCI bus to provide point-to-point and dedicated bus access. Data is transferred in packets through pairs of transmit and receive signals called lanes, each supporting up to 250 MB/s bandwidth per direction. Thus, a multi-channel serial design increases the flexibility of the PCI Express bus - devices needing lesser bandwidth may be given a single lane (x1) at 250 MB/s bandwidth per direction, while devices requiring faster bandwidth can be given more lanes at up to x32 lane width.
Bandwidths of standard PCI Express lanes
A PCI Express card is also capable of down-width support that enables installation of a card with a smaller-width lane to a larger-width PCI Express slot. For example, a x1 card may be installed without any problem in a x4 or x16 slot.
The PCI Express architecture consists of a Transaction Layer, a Data Link Layer, and a Physical Layer. While PCI Express is based on existing PCI architecture, cards and systems may easily be converted to PCI Express by changing only the physical layer. The software layer is fully-compatible between PCI and PCI Express. This scalability allows existing systems to adopt PCI Express without any change in the software.
Why PCI Express®
While the PCI bus has been the mainstream I/O interconnect for many years because of its plug-and-play capability and bandwidth (33 MHz and 32-bit with a theoretical bandwidth up to 132 MB/s), the technology is showing signs of age and growing insufficient for current high-bandwidth cards. Until recently, the PCI bandwidth is shared by more processing-intensive devices such as gigabit LAN and high-performance graphics cards that utilize higher bandwidth percentages. Promising to deliver higher bandwidths than PCI, PCI Express - formerly known as 3GIO (Third-Generation Input/Output) - is created and adopted by more and more consumer, commercial, and industrial PCs.
The need for PCI Express in data acquisition
In some high-channel count simultaneous sampling, high-speed data acquisition, and multi-task measurement applications, existing PCI bus technology may not be able to satisfy the high-bandwidth requirements of both hardware peripherals and software applications. PCI Express provides an opportunity to break the PCI bus bandwidth barrier and achieve superior system performance and responsiveness. In addition, migrating to PCI Express is a practical choice as more and more motherboards offer PCI Express slots exclusively.
ADLINK plus PCI Express equals breakthrough data acquisition
The ADLINK DAQe-2000 Series cards bring all the benefits of PCI Express to data acquisition. Supporting resolutions of 12 to 16 bits, sampling rate of 250 kS/s to 3 MS/s, and four to 96 channels, the DAQe-2000 Series cards deliver unmatched performance for simultaneous-sampling, multiplexing, and waveform generation. The DAQe-2000 Series showcases ADLINK's agility in providing timely solutions that are relevant with current technological advances.
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