Google+ Facebook Twitter Pin It Reddit

Jameco Challenges

Western Design Center Products

By Robert Cong

The Foundation of Microprocessor Design

The saying "the newer, the better" doesn't exactly apply when it comes to semiconductors. In fact "oldie, but goodie" comes to mind for many chips created decades ago that are still used today. They have stood the test of time because they simply work well. Different topologies will be designed, but the core stays the same. When the first microprocessor was made in 1971, its design was used to build upon the famous 8080 CPU by Intel. The 65xx family of 8-bit microprocessors was introduced in 1975 and is still going strong thanks to manufacturers like Western Design Center.


Western Design Center makes the 65xx brand of CMOS microprocessors. Part of the 65xx family is the 6502 chip, which was first designed in 1975 and was the least expensive, full-featured microprocessor on the market in those days. The processor was used in a large number of designs for the first computers for homes and businesses such as the Apple I and Apple II computers in 1976 and 1977. Even more popular than an Apple computer in the mid 1980s, was the Commodore family of computers and the Nintendo Entertainment System, which both also utilized the 6502 in their systems.
1977 Apple II 8-bit Home Computer
1977 Apple II 8-bit Home Computer
1982 Commodore 64 8-bit Home Computer
1982 Commodore 64 8-bit Home Computer
1985 Nintendo Video Game Console
1985 Nintendo Entertainment System 8-bit Video Game Console

At COMDEX '96 (one of the largest computer trade shows in the world), the 6502 was honored as one of seven microprocessors having the most impact on the Information Technology industry in the past 25 years. These processors have been used since the beginning stages of computers and the embedded microprocessor development of PCB, ASIC and FPGA products.

The 6502 first started as an 8-bit processor with a 16-bit address bus and very few registers. These days, the possible number of transistors able to be put onto a single chip has exponentially grown, allowing designers such as Western Design Center to make a 16-bit processor with much more address space and registers. Western Design Center's founder, Bill Mensch, recreated the original 6502 chip and made it possible to operate on lower power while keeping all the key components which set the 6502 apart from other processors.


These chips are far from obsolete today. From hobbyists and DIYers to big corporations, the 65xx chips are relevant in almost every field. In the medical field, places like St. Jude's Children's Hospital and Medtronic make medical devices using the 65xx chips to create defibrillators and mammogram devices. Nuvoton and Motu make use of the 65xx family by creating audio devices, hall-effect sensors and handheld video games/educational devices. Computer enthusiasts building their own home-brew computers also use the 65xx because of its I/O expandability. Similar processes have been used in grocery stores when controlling the temperature of different sections in the store. Having the ability to control more devices opens the door for an even wider range of possibilities.

MOTU Microexpress Unit Display
MOTU Microexpress Unit Display

Defibrillator design
Defibrillator Design Uses the 65xx Family of Products

Defibrillator design


Today, Western Design Center products include microprocessors, versatile interface adapters and peripheral interface adapters .

The microprocessor units come in both 8-bit and 16-bit configurations. They consume low power and can provide up to 65,536 bytes of memory space with a 16-bit address bus. They are the next generation of the first 6502 chips. They are also backwards-compatible with one another, meaning you can write to one another although they are different processors. The new 65xx MPUs are a CMOS extension of the 6502, with additional instructions and scalable functionality. The architecture of this popular microprocessor has been used in a great number of applications such as computers, video games, telephones, cameras, security systems, medical devices, industrial controllers, and much, much more.

16-bit Microprocessor
16-bit Microprocessor in PLCC and PDIP Packages

To be used with the microprocessors are the microcontroller units (MCUs), versatile interface adapters (VIAs), and peripheral interface adapters (PIAs). What intrigues people towards these products is the expandable I/O functionality, which allows users to program each input/output by simply hooking up the data bus and setting the address lines accordingly.

MCUs feature embedded debug monitor ROM, a debug port UART with baud rate timer, and monitor "watch dog" timer with "restart" interrupt. They're based off the 6502 core, so you can be assured that reliability will not be an issue.

16-bit Microcontroller
16-bit Microcontroller

VIAs combine flexible I/O control with the versatility of two 16-bit timers. They include functions for programmed control of two peripheral ports for interfacing directly between the microprocessor and selected peripheral units. These adapters come in both PLCC and PDIP packages.

PIAs are very flexible with two 8-bit bidirectional I/O ports with per bit data direction control and four programmable interrupt control lines (two for each port). They interface to the 65xx MPUs with a reset line, a 2 clock line, a read/write line, two interrupt request lines, two register select lines, three chip select lines and an 8-bit bidirectional data bus. They also interface to the peripheral devices using four interrupt/control lines and two 8-bit bidirectional buses. Both PLCC and PDIP packages are available.

The bottom line is that these products have been around for quite some time now and the reason why they have done so is because they work – and work well. These chips have shown that they are dependable and have maximum functionality while taking up minimum real estate. If you ever need any support or ideas with your application, there's a website and forum filled with very helpful people who know the architecture inside and out at With computer technology advancing at its rapid rate and having these ICs stick around for this long, you know you have a winner.

For more information on the 6502 processor, Bill Mensch or Western Design Center, check out the following links:

Robert is a graduate from Cal Poly, San Luis Obispo in Electrical Engineering. He is from Lincoln Heights in Los Angeles, CA. His interests include sports, movies, music and playing with cool, new gadgets.