Datasheet

118
4341H–MP3–10/07
AT8xC51SND2C/MP3B
The USB controller is then re-activated.
Figure 16-13. Example of a Suspend/Resume Management
16.10.3 Upstream Resume
A USB device can be allowed by the Host to send an upstream resume for Remote Wake-up
purpose.
When the USB controller receives the SET_FEATURE request: DEVICE_REMOTE_WAKEUP,
the firmware should set to 1 the RMWUPE bit in the USBCON register to enable this functional-
ity. RMWUPE value should be 0 in the other cases.
If the device is in SUSPEND mode, the USB controller can send an upstream resume by clear-
ing first the SPINT bit in the USBINT register and by setting then to 1 the SDRMWUP bit in the
USBCON register. The USB controller sets to 1 the UPRSM bit in the USBCON register. All
clocks must be enabled first. The Remote Wake is sent only if the USB bus was in Suspend
state for at least 5ms. When the upstream resume is completed, the UPRSM bit is reset to 0 by
hardware. The firmware should then clear the SDRMWUP bit.
USB Controller Init
Detection of a SUSPEND State
SPINT
Set SUSPCLK
Disable PLL
microcontroller in Power-down
Detection of a RESUME State
WUPCPU
Enable PLL
Clear SUSPCLK
Clear WUPCPU Bit
Clear SPINT