Chapter-01: USB architecture and characteristics

1-1 What is USB?
USB: 1995, Compaq, Digital Equipment Corp, IBM, Intel, Microsoft, NEC, and Northern Telecom
USB 1.0: 1996
USB 1.1: 1998, Compaq, Intel, Microsaoft, and NEC
USB 2.0: Year 1999, + Hewlett Packard, Philips, Lucent
USB advantages:

• Unified interface
• Plug-and Play
• Hot Attach & Detach
• USB 2.0 up to 480Mbps
• Supporting maximum 127 devices
• Device power maximum 5V/500mA, typical 5V/100mA

1-5 USB transfer type

• Control transfer: Control read, control write, and no data control
• Interrupt transfer
• Bulk transfer: Resend , if transfer error. (USB 2.0 max. 56MB/s)
• Isochronous transfer

USB 1.0 and USB 1.1 : 1ms frame
USB2.0 : Divide 1ms frame to 8 microframe. (1 microframe = 125us)

1-6 USB conecttor and cable
http://en.wikipedia.org/wiki/Universal_Serial_Bus

• PC Host: There are two 15K ohm resisters to pull down D+ and D- lines.
• Full Speed device: D+ pull up a 1.5K ohm
• Low Speed device: D- pull up a 1.5K ohm
• The data cables for USB 1.x and USB 2.x use a twisted pair to reduce noise and crosstalk.
• Differential 1: (D+) - (D-) > 200mV, Differential 0: (D+) - (D-) < 200mV
• J state: Full speed device: Differential 1, Low speed device: Differential 0
• K state: Full speed device: Differential 0, Low speed device: Differential 1
• IDLE: Full Speed device: D+ > VIHZ(min), D- < VIH(min)
• IDLE: Low Speed device: D- > VIHZ(min), D+ < VIH(min)
• SOP: IDLE (J)- > K