Introduction to PIC and Embedded Systems

1. Introduction to PIC and Embedded Systems

2. What is Embedded System? • If we take any engineering product that needs control, and if a computer is incorporated within that product to undertake the control, then we have an embedded system. OR, • A system whose principal function is not computational, but which is controlled by a computer embedded within it.

3. Examples of an Embedded System • The derbot Autonomous Guided Vehicle (AGV) • Two microswitch bump detectors • ultrasound detector • Two light sensors • compass as navigational system • Locomotion is provided by two geared DC motors • piezo-electric sounder is included for the AGV to alert its human user

6. Instruction sets – CISC and RISC • CISC • many instructions and considerable sophistication. • Complexity of the design tends to lead to slow operation. • RISC • Each instruction is contained within a single binary word. • Every instruction normally takes the same amount of timeto execute.

7. Organizing memory • Von Neumann • The computer has just one address bus and one data bus. • Simple and logical, and gives a certain type of flexibility. • Disadvantage: If the CPU is accessing program memory, then data memory must be idle and vice versa. • Harvard structure • Every memory area gets its own address bus and its own data bus. • Greater flexibility in bus size, but pay for it with a little more complexity • Disadvantage: Reinforces the distinction between program and data memory. Example, when data is stored in program memory as a table, but is actually needed in the data domain.

9. Microprocessors and microcontrollers • Microprocessors: • These were amazing devices, which for the first time put a computer CPU onto a single IC. • At first, all other functions, like memory and input/output interfacing, were outside the microprocessor. • The development of the microprocessor led very directly to applications like the personal computer.

10. Microprocessors and microcontrollers • Microcontroller: • No need for high computational power, or huge quantities of memory, or very high speed. • Special category of microprocessor emerged that was intended for control activities, not for crunching big numbers. • After a while this type of microprocessor gained an identity of its own, and became called a microcontroller. • The microcontroller took over the role of the embedded computer in embedded systems.

11. Microcontrollers • Primarily, it must have excellent input/output capability • Because many embedded systems are both size and cost conscious, it must be small, self-contained and low cost. • May need to put up with the harsh conditions of the industrial or motor car environment, and be able to operate in extremes of temperature.