AT90USB646 datasheet(294/434 Pages) ATMEL

294 / 434 page

294

7593A–AVR–02/06

AT90USB64/128

USB host controller state after an hardware reset is ‘Reset’. When the USB controller is enabled

and the USB Host controller is selected, the USB controller is in ‘Idle’ state. In this state, the

USB Host controller waits for the Device connection,

with a minimum power consumption.

The USB Pad should be in Idle mode. The macro does not need to have the PLL activated to

enter in ‘Host Ready’ state.

The Host controller enters in Suspend state when the USB bus is in Suspend state, i.e. when the

Host controller doesn’t generate the Start of Frame. In this state, the USB consumption is mini-

mum. The Host controller exits to the Suspend state when starting to generate the SOF over the

USB line.

23.4 Device Detection

A Device is detected by the USB controller when the USB bus if different from D+ and D- low. In

other words, when the USB Host Controller detects the Device pull-up on the D+ line. To enable

this detection, the Host Controller has to provide the Vbus power supply to the Device.

The Device Disconnection is detected by the USB Host controller when the USB Idle correspond

to D+ and D- low on the USB line.

23.5 Pipe Selection

Prior to any operation performed by the CPU, the Pipe must first be selected. This is done by:

• Clearing PNUMS.

• Setting PNUM with the Pipe number which will be managed by the CPU.

The CPU can then access to the various Pipe registers and data.

23.6 Pipe Configuration

The following flow must be respected in order to activate a Pipe:

AT90USB646 Datasheet(PDF) 294 Page - ATMEL Corporation