Silicon Laboratories Stepper Machine Specifications download pdf (Page 37)

USB—Device States (1 of 3)

 Idle state

 All drivers are off. Device speed determines Idle state based on the pull-up

resistor attached. For full speed D+ is more positive than D- and vice versa

for low speed.

 Suspend state

 Low power state with < 500 uA current consumption requirement. If remote

wake-up capable then it is < 2.5 mA.

 Remote wake-up — device has the ability to notify the host to start

transactions.

 Timeout

 After 3 mS of inactivity on the bus all devices are required to enter the Suspend

state

 SOF marker devices keep devices out of suspend

 Global suspend when host goes into standby

 Selective suspend

 Host can issue Set_Port_Feature request to put a specific device

into suspend

After power up and throughout the enumeration process the MCU enters/exits several

device states

There are different device states defined in the USB specification. Take a minute to

familiarize yourself with those outlined here.

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Silicon Laboratories Stepper Machine Specifications Page 37