High Speed USB


  • USB High Speed was introduced in the year 2000 as part of the USB 2.0 specification.
  • Maximum theoretical bandwidth is 480 Mbit/s.
  • Uses four data lines - Power (5 V), Ground, and two data lines (D+ and D-).
  • Half-Duplex differential signaling on D+ and D-.
  • Uses the traditional USB connectors.


High-speed devices begin the enumeration process identical to full-speed devices. High-speed devices announce to the Host that they are ready to be enumerated by asserting a 5 V signal on D+ through the use of a 1.5 kΩ pull-up resistor. During the 20 ms enumeration RESET signal sent by the Host, the Device executes the High-Speed negotiation process. Upon completing this negotiation the Device, Host, and Hub port connecting the Device will operate in High-Speed mode.

Differences with Full Speed USB


High-speed USB was designed to coexist with full-speed USB. The designers speculated many systems would have a Host that could simultaneously offer support for full and high-speed devices. To achieve compatibility, eight high-speed microframes are completed within 1 ms.

Frame Size and Transfer Types

HIGH SPEED Frame size: 125 μs

Size of
per frame
Control 64 bytes 1 64 kByte/s
Interrupt 1024 bytes up to 3 24 MByte/s
Bulk 512 bytes up to 13 53 MByte/s
Isochronous 1024 bytes up to 3 24 MByte/s

USB Bus States and Signal Levels

Bus States
Bus Levels
Differential "1" D+ high , D- low
Differential "0" D+ low , D- high
Single Ended 0 (SE0) D+ low , D- low
Single Ended 1 (SE1) D+ high, D- high Invalid condition!
Data J state Differential "1"
Data K State Differential "0"
Idle Data J
Resume Data K
Start of Packet (SOP) switches from Idle to Data K
End of Packet (EOP) SE0 for 2 bits, followed by Data J for 1 bit
Disconnect SE0 >= 2 μs
Connect Idle for 2.5 μs
Reset SE0 >= 2 μs

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