Choosing the right microcontrollers

Details: Category: Blog; Published on Thursday, 14 February 2013 09:25; Hits: 11745

Embedded processors span the range from simple 8-bit microcontrollers like those at the heart of childrens toys, to powerful custom 64-bit microprocessors and specialized DSPs and network processors. Some of the products that include these chips run a short assembly program from ROM with no operating system; many more run real-time operating systems and complex multithreaded C++programs; and its also increasingly common to find variants of desktop-lite operating systems based on Linux and Windows controlling more powerful devices that are still clearly embedded systems.

If an application does not have very high demands on processing power, and is of relatively small size, then it can make sense to consider an 8-bit microcontroller. 8-bit microcontrollers should typically be considered for applications that are dedicated to just doing one job, with a limited user interface and little data processing.

8-bit microcontrollers

8-bit microcontrollers come in all sizes from small 6-pin devices to chips with 64 pins. They have flash sizes ranging from 512 bytes to 256KB, SRAM sizes from 32 to 8KB, or more, and EEPROM from 0 to 4K, or more. A minimal system can be as simple as a single chip, with a bypass capacitor on the power supply rail.

The three most popular lines of 8-bit microcontrollers are the 8051 series, the PIC series from Microchip, and the AVR series from Atmel, now part of Microchip.

16-bit microcontrollers
16-bit microcontrollers are the next step up from 8-bit, while still sharing many of the same attributes. They are faster, support even more peripherals, and generally offer more memory, both flash and SRAM.

In addition to more IO pins, most of them also have hardware multipliers that are significantly faster, and use less program memory, compared to pure software implementations.It is easy to find devices that have both ADC’s and DAC’s, or devices with capacitive touch sensors, segmented LCD drivers and Ethernet.

Internally, these devices also have hardware blocks typically not found in lower end devices. These include encryption engines, Operational or Programmable Gain Amplifiers, and DMA controllers.

16-bit microcontrollers can be found from various manufacturers such as Microchip (dsPIC33 is a popular choice), NXP, Infineon, Cypress, and the TI MSP430 series.

32-bit microcontrollers

32-bit microcontrollers are powerful devices with microprocessor-like features. Some of the advanced features include instruction pipelining, branch prediction, Nested Vectored Interrupts (NVI), Floating Point Units (FPU), memory protection, and on-board debuggers.32-bit microcontrollers support Real Time Operating Systems (RTOS) that, in turn, provide multitasking capabilities.

Two prominent vendors of ARM-based chips are Atmel with their SAM device line, and STMicroelectronics with their STM32 line of products.In general, the STM32 devices offer more choices, and should be given top consideration when designing in an embedded 32-bit microcontroller.