Microcontroller architectures, then and now

A quick look at two microcontrollers from different eras shows how far the industry has come.

The Intel 8051, which dates from 1980, has 128 bytes of RAM, 4 kbytes of ROM, four bidirectional I/O ports, one UART and two 16-bit timers. The Freescale MC9S12X, launched in 2007, packs 32 kbytes of RAM, 4 kbytes of E²PROM, 512 kbytes of flash, six UARTs, three SPI interfaces, an eight-channel timer, an eight-channel 10-bit ADC, an eight-channel PWM module, five CAN interfaces, two I²C interfaces, a periodic interrupt timer and an X-gate parallel-processing module.

There are many applications that will never need more than 8 bits of processing power. But the 32-bit microcontroller is becoming more common as modern system design demands more processing clout. With shrinking designs and with an extra emphasis on low-power operation and standby, 32-bit microcontrollers are finding their way into more applications.

Multicore

Another factor in the battle for processing supremacy is the use of multiple processing cores to perform multithreading. Multicore devices are common in PCs, laptops and servers but are also starting to be seen in microcontrollers for certain processing-intensive applications, such as industrial equipment and car navigation systems.

Die photograph of a 2007 Freescale MC9S12X microcontroller

As flash memory technology has improved, the silicon real estate required for flash has shrunk. Embedded flash has started to replace other programmable ROM as the program storage of choice because of the speed of the program/erase cycle. And more bytes of this memory are being incorporated into microcontrollers.

Also finding its way into microcontrollers is digital signal processing functionality. Processor cores for control are different from those that perform very complex mathematical functions. Cores that perform both functions are blurring that line.

In some cases, DSP-like mathematical functions are being added to a regular core's instruction set, with the hardware to support it. And the opposite is occurring too, as DSP cores add control-like instructions.

An alternative is to embed both a controller and a DSP core in the same device, creating a hybrid. Whether these devices are considered microcontrollers with DSP functionality or DSPs with microcontroller functionality is up to the vendor to decide.

Large semiconductor vendors that produce microcontrollers are now trumpeting the fact that their applications or systems engineers can help you design your system using their wide variety of parts. Smaller microcontroller vendors are doing the same thing, only by cooperating with system design houses to create reference designs.

Steve Bitton (sbitton@techinsights.com) is a technology analyst at TechOnline, a division of TechInsights. He has a bachelor's of applied science degree in electrical engineering from Queen's University (Kingston, Ontario).

Technical course: Fundamentals of Microcontrollers.