atmel avr 8 bit risc microcontrollers a general comparison
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ATMELAVR 8 bit RISC
MICROCONTROLLERS
a general comparison
What does AVR RISC mean?
• The acronym AVR has been reported to stand for: Advanced Virtual RISC and also for the chip's designers: Alf-Egil Bogen and Vegard Wollan who designed the basic architecture at the Norwegian Institute of Technology.
• RISC stands for reduced instruction set computer.
CPU design with a reduced instruction set as well as a simpler set of instructions (like for example PIC and AVR)
A little history
• The PIC (Programmable Interrupt Controller) appeared around 1980.→ 8 bit bus → executes 1 instruction in 4 clk cycles→ Harvard architecture
• AVR (1994)→ 8 bit bus→ one instruction per cycle→ Harvard architecture
AVR 8-Bit RISC High Performance
• True single cycle execution→ single-clock-cycle-per-instruction execution → PIC microcontrollers take 4 clock cycles per instruction
• One MIPS (mega instructions per second) per MHz → up to 20 MHz clock
• 32 general purpose registers→ provide flexibility and performance when using high
level languages → prevents access to RAM
• Harvard architecture → separate bus for program and data memory
AVR 8-Bit RISC Low Power Consumption
• 1.8 to 5.5V operation
→ will use all the energy stored in your batteries
• A variety of sleep modes
→ AVR Flash microcontrollers have up to six different sleep modes
→ fast wake-up from sleep modes
• Software controlled frequency
AVR 8-Bit RISC Compatibility
• AVR® Flash microcontrollers share a single core architecture
→ use the same code for all families
→ 1 Kbytes to 256 Kbytes of code
→8 to 100 pins
→ all devices have
Internal oscillators
AVR 8-Bit RISC - picoPower Technology
• “PicoPower enables AVR to achieve the industry’s lowest power consumption with 650 nA with a RTC (real time clock) running and 100nA in Power Down sleep” (from ATMEL website)
• - True 1.8V Supply Voltage- Minimized Leakage Current- Ultra Low Power 32 kHz Crystal Oscillator- Digital Input Disable Registers- Power Reduction Register
So what chip should I use?
• the application chooses the chip• each family has a large number of variants • the number of pins, the package, the cost
of the chip, the peripherals, the operating voltage, the current consumption, and so forth
• PIC is more application oriented• AVR mostly pin #s and flash memory
differ
Many choices
• TI(MSP430), Zilog (Z8), Freescale (SC8), Atmel(AVR), Microchip (PIC), ST, Renesas / Hitachi (Mx or H8), Philips (8051) as just few of the many possible selections
• MICROCHIP ATMEL and MSP430
→ FREE SAMPLES
AVR has very good documentation
• Wide use
• AVRFreaks .net
• Free software
Most Importantly!!!
• Best C compiler to start programming in C→ and it is FREE
Code Vision AVR→ http://www.hpinfotech.ro/
• AVR Studio 4 also free from: http://www.atmel.com/dyn/products/tools_card.asp?tool_id=2725
Code Vision AVR setup
• After opening Code Vision AVR click on:
→ tools
→ codewizardAVR
select you chip version and oscillator frequency
Set/clear the pins you want
LCD setup (LCD from microprocessors lab)
• Control LCD with port A:
Setting up the Analog to Digital conversion
• 8 bit A/D on channel 3 (PORTA.3)
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