Peripheral Component Interconnect

The Peripheral Component Interconnect, or PCI Standard (in practice almost always shortened to PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard.The PCI Bus is a high performance bus for interconnecting chips, expansion boards, and processor/memory subsystems.

• Wiki article on PCI

Non-Return-to-Zero Inverted

NRZI encoding is used for data transmission in the standard USB.
http://en.wikipedia.org/wiki/NRZI

EIA standards :RS232/422/485

RS 232,422,485 -quick reference

RS 232 tutorial - A very informative webpage - Recommended

Selecting and Using RS-232, RS-422, and RS-485 Serial Data Standards
An application note from Maxim semiconductors.Includes connection firures for RS232.422,485 and specifications

Dallas Semiconductor application note on RS232 - simple

RS422/485 application note

Comparing Bus Solutions

Texas Instruments Application Report "Comparing Bus Solutions" February 2004, Texas Instruments,

USB On-The-Go

Every USB communications is between a host and a device. Devices can't communicate with each other directly. The On-The-Go supplement to the USB specification defines a new type of device that can function as both a device and as a scaled-back host (but not both at the same time). When functioning as a device, the On-The-Go device can communicate with a PC or other USB host. When functioning as a host, the device can connect to USB peripherals.

• USB On-The-Go: a Tutorial
• Introduction to USB On-The-Go

Universal Serial Bus

• Home of USB Implementers Forum, Inc.
• USB 2.0 specification
• USB Central
• Wiki article on USB
• Short, simple description of USB with good pictures of cable breakdown and plugs
• USB in a nut shell