Electronic Design

21st Century Technology Extends Life Of 8-Bit MCUs

Many designers using 8-bit 8051 microcontrollers as the core of their systems face a challenge when updating the performance of their designs. Historically, performance upgrades have often required a transition to a 16-bit MCU or a digital signal pro-

cessor (DSP), creating unwanted complexity and expense in an innovative design. But companies are bringing 21st century technology to an established, reliable 8051 architecture, enabling designers to extend the longevity of their system and eliminating the need to pursue painful upgrades to alternate architectures.

The original 8051 CPU was designed in the late 1970s, when the economics of ICs favored low transistor counts over raw performance. As a result, the original 8051 implementation spread each instruction across 12 clock cycles to minimize the hardware resources required. In 1991, Dallas Semiconductor (now Maxim Integrated Products) advanced the 8051 architecture with a new implementation that removed redundant bus operations and reduced the typical instruction to only four clock cycles.

These devices gave users a drop-in replacement that required no software changes yet produced an immediate threefold improvement in performance. However, little was done to further improve the 8051 architecture after the early 1990s, forcing designers to consider abandoning the 8051 to improve their systems' performance.

In the late 1990s, the 8051 architecture underwent a radical change that increased the typical throughput by an order of magnitude—up to 100 MIPS. A number of products are now available that leverage the 8051 instruction set architecture in new, proprietary implementations that allow modern MCUs to maximize the instruction throughput while retaining complete object-code compatibility.

By applying contemporary techniques to an established instruction set architecture—specifically, advanced design and verification methodologies—it is possible to create a "hard-wired" implementation of the C8051F CPU. The instruction set is mapped to a basic two-stage pipeline to increase throughput while maintaining an 8-bit program memory width. The result is a much more efficient implementation of the 8051 instruction set, providing a 20× performance improvement over the original 8051.

The enhancements to the 8051 do not stop there. By integrating precision analog on-chip, the designer gains bill-of-materials savings and performance enhancements. It is also possible to eliminate the need for standalone analog peripherals by including fully specified and tested analog and mixed-signal functions, further simplifying the system design.

Modern technology also allows the addition of in-system debug. Although widely available in 32-bit MCUs and high-end DSPs, very few 8-bit MCUs offer in-system debug capabilities. But with a fresh look at the 8-bit MCU, the addition of seamless in-system debug functionality provides users with a very low cost of entry, as well as an excellent user experience.

Today, industry analysts predict that the 8-bit MCU market represents a large opportunity, with more than 4.2 billion 8-bit MCUs expected to ship in 2007. However, when you consider the trend toward leveraging 8-bit 8051 MCUs in consumer, industrial, and automotive applications that historically used complex and expensive ASICs, DSPs, and standalone analog ICs, the addressable market could potentially double in size.

Bringing 21st century technology to an established, reliable 8051 architecture enables designers to extend the longevity of their system and eliminates the need to pursue difficult upgrades to alternative architectures. Today's modern ingenuity has breathed life into a timeless market by combining the 8051 architecture with high-performance analog, thereby decreasing the bill of materials while improving performance—the ultimate dream for designers.

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