Designing Embedded Hardware, 2nd Edition

Chapter 15. The AVR Microcontrollers

A really useful engine...

—W.V. Awdry

In this chapter, we'll look at the Atmel AVR processor. Like the PIC, this processor family is a range of completely self-contained computers on chips. They are ideally suited to any sort of small control or monitoring application. They include a range of inbuilt peripherals and also have the capability of being expanded off-chip for additional functionality.

Like the PIC, the AVR is a RISC processor. Of the two architectures, the AVR is the faster in operation and arguably the easier for which to write code, in my personal experience. The PIC and AVR both approach single-cycle instruction execution. However, I find that the AVR has a more versatile internal architecture, and therefore you actually get more throughput with the AVR.

In this chapter, we'll look at the basics of creating computer hardware by designing a small computer based on the AVR ATtiny15. We'll also see how you can download code into an AVR-based computer and how it can be reprogrammed in-circuit. From there, we'll go on to look at some larger AVR processors, with a range of capabilities.

Later in the chapter, we're going to look at interfacing memory (and peripherals) to a processor using its address, data, and control buses. For most processors, this is the primary method of interfacing, and, therefore, the range of memory devices and peripherals available is enormous. You name it, it's available with a bus interface. So, knowing how ...