COSMOS Summer 2008 Necessary Electronics Rajesh K. Gupta Computer Science and Engineering University of California, San Diego. 2008 R. Gupta, UCSD

Roadmap Topic: This lecture Next lecture Reference Keywords: Electronics you need to know This lecture Concepts covered: “Open Drain”, Clock, Memory, Address Space Next lecture The I2C Interface Reference None Keywords: Electrical Signals Circuit Schematics, DRAM, Flash memories Resistors, Capacitors, Analog, Digital Waveforms, 2008 R. Gupta, UCSD

A bit about electronics Electronics is all about movement or storage of electrons (Negatively charged particles) A collection of electrons represents a certain amount of charge A collection of charge creates an electrical field around it Since charges attract or repel each other, this is expressed as a voltage difference that makes a charged particle to move An electron moves from low voltage to high voltage Which is same as a current movement from high voltage to low voltage. 2008 R. Gupta, UCSD

A bit more Electrical current is caused by movement of electrons in an electric field Voltage, Current and Ohm’s Law Reference Voltages: Power, Ground An electrical circuit represents a complete path for flow of current A signal waveform represents change of voltage at a point in a circuit over time DC and AC components of a waveform. Analog versus Digital. Finally, what are circuit schematics? Components. 2008 R. Gupta, UCSD

Some Common Components Passives Resistors, Potentiometers Capacitors Inductors Actives Diodes, LED Transistors Crystals, Oscillators 2008 R. Gupta, UCSD

Questions to ponder Communications? What and How Among humans Among machines What are the possible ways machines can communicate? What medium do they use? Electrical wire or wireless What do they communicate? Analog versus digital How they communicate? Serial versus Parallel What else? 2008 R. Gupta, UCSD

A Processor’s Interfaces We talked about Memory last time: RAM, ROM What are various memory blocks? DRAM, SRAM, Flash How is a memory ‘addressed’? What is an address space? How do we communicate to a ‘peripheral’? 2008 R. Gupta, UCSD

Recap Electrical signaling typically consists of voltage change waveform over time Can be analog or digital Computers interfaces with devices via memory or via direct ports Next: I2C interface. 2008 R. Gupta, UCSD