Lecture 7: Overview Microprocessors / microcontrollers. Device architectures Software development High level languages The EXAM

Microcontrollers / Microprocessors Computer on a chip IO memory often application specific Cheap often used in embedded systems. Microprocessor CPU ALU registers. Needs external memory. Example use: personal computers.

Components of a Microprocessor (or CPU in a PIC)

Some components of a microprocessor. Buses - Address: Carries memory address Data: Caries data from and to memory Control: Signals used to sequence operations Control Unit- Generates control sequences based on Instruction Register Arithmetic Logic Unit: Does the sums! Registers: General purpose (store numbers) Program Counter (address of next instruction) Status Register (flags like carry bit/zero etc) Instruction Register (instruction being executed)

Architecture / buses How components are connected.

Types Architecture. Von Neumann Harvard Cellular?

Von Neumann (most microprocessors) Single memory for DATA and PROGRAM Shared bus (Von Neumann bottle neck)

Harvard (microcontrollers / DSP chips) Separate memory for DATA and PROGRAM Different buses (may different widths)

Software development for the PIC. Specify requirements. Write assembly code using an editor. Compile into machine code (assembler) . Fix compile time errors Program the pic (e.g. PICKit3) Fix run time errors ( go back to step 2.) It Works!

Incremental / Evolutionary Development Large complex systems are difficult to write/debug Start with a simple system and add complexity. Use routines to “encapsulate” functionality and allow easy reuse of code.

Integrated Development Environment IDE A program that manages the development process .e.g. MPLABx Automates the process (hides some of the details!)

Other Microchip devices

Typical Features. GPIO (general purpose IO pins) Interfaces: SPI I2C UART Ethernet USB PWM generators (motor control) ADC (less common DAC) Signal processing Timers More interrupts

Other manufacturers Texas Instruments Atmel e.g. MSP430 . . . have similar hardware / software. Texas Instruments e.g. MSP430 Atmel AVR general purpose ARM (Linux android MS windows)

RISC (Reduced Instruction Set Computers) RISC is a common type of instruction set. Examples: ARM (Advanced RISC Machine) Widely used 32bit instruction set MIPS Microprocessor without Interlocked Pipeline Stages (e.g. Play-station)

High level languages Different devices have different: Architectures Instruction sets A compiler can translates a high level languages program (C C++ . . .) into machine code for the target device

Arduino . . is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments. Various boards (different manufacturers) Open source IDE (Linux, Windows, mac OS X) High level C++ based programming language. Libraries to help you do things !!!!

Showing how easy it is to write to the LCD display! Arduino IDE Showing how easy it is to write to the LCD display!

Applications of microcontrollers Automotive Home entertainment Industrial Automation Metering PC Peripherals Etc. . . . .

Summary Students should understand: Assembly code and it's relationship with machine code. Understand the components of the PIC and microprocessors The different architectures and there merits. How to program in assembly code for the PIC16F84. How to interface to SPI devices. How to interface to parallel devices ( LCD display).

Exam 1 Hour 2 sections each with 2 questions PJL / CTC. Answer 2 questions, one from each section. Instruction set from PIC16F84 will be provided. See: http://people.bath.ac.uk/eespjl/courses/Embedded/Resources/DATASHEETS/ PIC16F84A_EXAM_SUMMARY.pdf