AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 252

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

21.4.2
21.4.3
252
AT90USB64/128
Power-on and reset
Interrupts
The software anyway has to select the mode (Host, Device) in order to access to the Device
controller registers or to the Host controller registers, which are multiplexed. For example, even
if the USB controller has detected a Device mode (pin ID high), the software shall select the
device mode (bit HOST cleared), otherwise it will access to the host registers. This is also true
for the Host mode.
The next diagram explains the USB controller main states on power-on:
Figure 21-9. USB controller states after reset
USB Controller state after an hardware reset is ‘Reset’. In this state:
After setting USBE, the USB Controller enters in the Host or in the Device state (according to the
IP pin). The selected controller is ‘Idle’.
The USB Controller can at any time be ‘stopped’ by clearing USBE. In fact, clearing USBE acts
as an hardware reset.
Two interrupts vectors are assigned to USB interface.
• The ID bit is cleared by hardware when a low level has been detected on the ID pin. The
• USBE is not set
• the macro clock is stopped in order to minimize the power consumption (FRZCLK=1),
• the macro is disabled,
• the pad is in the suspend mode,
• the Host and Device USB controllers internal states are reset.
• The DPACC bit and the DPADD10:0 field can be set by software. The DPRAM is not cleared.
• The SPDCONF bits can be set by software.
Device controller is then disabled and the Host controller enabled.
Clock stopped
Dev ice
FRZCLK=1
Macro off
USBE=1
ID=1
USBE=0
Reset
USBE=1
ID=0
USBE=0
RESET
USBE=0
Host
HW
USBE=0
<any other
state>
7593A–AVR–02/06