Issue 109, August 1999
Using System-on Chip Design with Virtual components

VC Functions

Numerous factors can lead to a decision to license a commercial VC for inclusion in an SOC design. The expertise and resources available and the time-to-market requirements for the end product must be balanced against the expense of the VC license. Even a company with vast, expert resources may be able to produce a better product faster by leveraging external IP.

This is especially true if the VC implements a common function because little is gained by designing and optimizing such a function rather than focusing on product-differentiating features. For example, the VC may duplicate the function of existing stand-alone chips (e.g., a UART or a floppy disk controller) or implement a common arithmetic function such as a multiplier.

Perhaps the highest leverage is provided by a VC that implements a formal or de facto standard. Because many types of chips and end products must meet a standard, a VC that implements this standard is ideal as a commercial IP product. It’s rare that an end user can add enough value with an in-house design to offset the time savings and standards expertise embodied in a well-designed VC.

The standards provided by VCs range from formal IEEE, ANSI, and IEC specifications to new technologies. Examples include communications protocols like Ethernet and ATM, computational functions such as MPEG and JPEG, parallel interconnect standards such as PCI and AGP, and serial interconnects like USB and IEEE 1394. These examples have wide applicability to many different types of SOC-based products, and the standards themselves are well enough defined to allow implementation as a VC.

A VC implementing an interconnect technology probably has the widest range of application. For example, PCI is used in diverse types of electronic products. Although it was developed as a personal computer peripheral bus, PCI has now been adopted for workstations, mainframe computers, military applications, and networking/telecommunications systems. USB is following a similar expansion of scope beyond the PC, as it is used to connect peripherals to gaming systems, set-top boxes, and PDAs.

The widest penetration of all may occur with 1394, which is designed to interconnect both computers and diverse consumer electronics devices. Products available today with 1394 support include video cameras, digital televisions, digital VCRs and professional audio equipment. Although it is not yet supported in mainstream PC chipsets, many desktop and laptop computers offer 1394 support and such peripherals as disk drives and videoconferencing cameras are starting to appear.