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Introduction to Atmel’s 8-bit AVR Microcontrollers

Introduction to Atmel’s 8-bit AVR Microcontrollers

Welcome to this module on the AVR 8-Bits Microcontroller family from Atmel. The module overviews the AVR 8-Bits Microcontroller family with emphasis on a brief overview .

AVR = Leading 8-bit Microcontroller

Atmel's low power, high performance AVR microcontrollers handle demanding 8- and 16-bit applications. With a single cycle instruction RISC CPU, innovative picoPower technology, and a rich feature set, the AVR architecture ensures fast code execution combined with the lowest possible power consumption.

Highest performance
The AVR core is a RISC architecture with a SISC instruction set. The device is also a Harvard architecture. The core actually provided a lot of powerful instructions that execute in single cycles. There is around 130 instructions on board in AVR. The designers can continue to write in C and let the C-compilers translate the code. Moving forward, it's single cycle execution, 20 MHz yields 20 MIPS, and one of the neatest things, when you talk about performance is the 32 general purpose registers that are actually onboard each AVR.

Best Code Density
The AVR was co-designed with AIR. AIR is a very well known C-compiler expert, and they made a lot of great recommendations on things to the core. The registers obviously help a lot. Some of the data pointers really help for code density. Why is code density important? Because if the design has smaller code, the engineer get to buy a smaller part. So, it saves the cost.

Lowest Power Consumption
So many things are going wireless, and so many devices are becoming battery powered, that power consumption is a very important thing. AVR has a new marketing term called picoPower. PicoPower is a new thing from AVR, and it leverages all the previous technology we have in lower power, and adds to it. One of the big differences with picoPower versus the other AVRs was the power save mode. It has gone and completely redesigned the 32 KHz oscillator to have a zero-power 32 KHz oscillator. That's allowing 0.6uA in power save with that oscillator running. Finally, in full run mode, it can do as low as 220uA per MIP in full active mode. These devices run from 1.8-5.5V. The 1.8V device is a true 1.8V device. That means that everything works at 1.8V. The designers can write to Flash, SRAM and EEPROM.

Best Memory Technology
Atmel is the first one to put Flash on a microcontroller. AVR also has the ability to protect your IP. So, there are lock bits, the designers can set inside the flash memory that actually make it unreadable to anybody else.

Best Integration
Integration is also important when looking at microcontrollers. Even on the small, little AVR devices, the designers will still see all the features on the large microcontrollers. Those are things like brownout detection, EEPROM, watchdog timers, debugging interfaces, calibrated RC oscillators, things like analog references, and real time counters. It lowers the system cost, makes the PCB smaller, reduces risk, lowers overall power consumption, and ultimately improves reliability.

AVR = Leading 8-bit MCU

This is what's made AVR so popular. It runs a 20 MHz 20 MIPS single cycle execution, Harvard architecture, 32 general purpose registers, very high performance microcontroller. Not only do you have the speed, but it's also best in class when it comes to code density.

The Scalable AVR Family
The AVR family is very scalable. So, whether the users are writing the code on a little 8-pin, 1K Flash tiny microcontroller, or put the code on a large, 256K Flash 100 pin. The code is going to completely port. The software you write on one is going to migrate through the rest of the family. It will help you as you're increasing or decreasing memory densities or changing your designs, it helps you to reuse a lot of the same code.

The Tiny Devices

Atmel AVR core got two families, Tiny and Mega. The code you write on one works on the other. Tiny is really specified that they're small parts, 28 pins and less, and Mega are bigger than that in terms of pin count. There is one other key difference that the Mega has a hardware multiplier onboard, but the small Tiny has the ability to have self-programming Flash memory. So in Tiny product family, there are a lot of different devices all in the same pin count with varying memory sizes. But all of these devices are pin to pin compatible with differing Flash memory sizes from 1K, to 2K, to 4K, to 8K.

Tiny Family Features
Some other key features in the Tiny family are listed here. Some of the devices have onboard temperature sensors. The overall family does run from 1K to 8K of flash, 64 bytes to 512 bytes of SRAM, and the same on the EEPROM -- so, onboard EE on the devices. The USI is a serial interface that allows it to run SPI or two wire interface, which is IIC compatible, anywhere from 6-20 I/O, up to two timers in the 8-bit space, and some of them have one 16-bit timer as well. It also has 5 PWMs, some of them, like the Tiny 261, 461, 861 family -- actually has a 64 MHz PLO on board so that you can get a high speed PWM. Some miscellaneous things include brownout detection, on-chip calibrated RC oscillators, watchdog timers, real time clocks. Again, it can operate from 1.8-5.5V. DebugWire is single wire debugging over the reset line. So the user can do hardware debugging on these without giving up 4 pins for JTAG. Here is the Mega family. Mega family ranges anywhere from 32 up to 100 pins. They have TQSPs, MLFs, and BGA package devices. Flash memory sizes go from 4K up to 256K. They also have advanced peripherals like LCD onboard up to 150 segments on some devices -- quite a range of products here. In the 32, 44, and 64, and 100, they are pin to pin compatible, Flash memory densities bearing anywhere from 16 up to 256K Flash pin to pin compatible.

Mega Family Features
The SRAM in Mega family runs anywhere from half a K up to 8K bytes of SRAM, and anywhere from 256-4K bytes of EEPROM. They have up to four USARTs onboard. 1 or 2 SPIs, and 1or 2 TWIs are IIC compatible. In general, it has 23-86 I/Os, multiple timers, up to four 16-bit timers depending on the device, as many as 16 PWMs onboard devices. The majority of the parts run from 1.8-5.5V, though some are 2.7-5.5. The Mega are going to be 16K of flash or larger with 32 pins or more, they have JTAG. If there's 16K or less, they'll have debugWire.

The ASSP Devices
ASSP stands for application-specific standard product devices. These are some of advanced peripherals in the Mega product line. So, USB is big, CAN, some lighting-specific devices, some devices specific for Smart Battery, and finally Zigbee as well.

Part Number Decoder
Here is shown the part number naming convention for Atmel AVR products. The U is the temperature grade. M is the package type. The "10" there is the speed grade. If there is a V or a low voltage part, it would have a "10" for a speed grade of 10. If it had no V there, it would have a 20 for a speed grade of 20. The P denotes a picoPower device.

part number decoder avr mcu

AVR Development Tools

Atmel provides the hardware tools and AVR Studio. So, in specific, AVR studio is a simulator, an editor and an assembler. It does have plug-ins for C-compilers, and it manages the hardware tools. It does all the updates for the users. It programs the devices.

First IDE with a Free C-compiler
When users open up AVR studio to begin the development work, rather than having to use a separate C-compiler, if they can downloaded GCC.

AVR C Compilers

AVR Studio is the new Integrated Development Environment (IDE) for writing and debugging AVR® applications in Windows® 9x/NT/2000/XP environments. It includes an assembler and a simulator. As far as C-compilers go, obviously you have freeware, which is GCC. It's called WinAVR, W-I-N-A-V-R. It's available at www.sourceforge.net. And, that's free of charge. It includes the plug-in to AVR studio.

AVR STK500 Starter Kit
the STK500 is a flagship starter kit and supports all of AVR devices. So, anything from the little 8-pin up to a 40-pin PDIP, you have the ability to program over multiple methods to do JTAG debugging, to do in-system programming, all of those different options, and everything's pinned out.

Additional Resources
Thank you for taking the time to view this presentation on the AVR 8-Bits Microcontroller family products. If you would like to learn more or go on to purchase some of these devices, you can either click on the link embedded in this presentation, or simple call our sales hotline. For more technical information you can either visit the site or if you would prefer to speak to someone live, please call our hotline, or even use our ‘live chat’ online facility.

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