AT80SND1C-ROTIL datasheet(96/210 Pages) ATMEL

96 / 210 page

AT8xC51SND1C

4109E–8051–06/03

Upstream Resume

A USB device can be allowed by the Host to send an upstream resume for Remote

Wake-up purpose.

Whe n

t he

U SB

co ntr o ll er

r e ceive s

th e

SET _F EAT URE

r equ est:

DEVICE_REMOTE_WAKEUP, the firmware should set to 1 the RMWUPE bit in the

USBCON register to enable this functionality. 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

clearing first the SPINT bit in the USBINT register and by setting then to 1 the SDRM-

WUP 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 com-

pleted, the UPRSM bit is reset to 0 by hardware. The firmware should then clear the

SDRMWUP bit.

Figure 67. Example of REMOTE WAKEUP Management

USB Controller Init

Detection of a SUSPEND state

SPINT

Set RMWUPE

Suspend Management

enable clocks

upstream RESUME sent

UPRSM

Clear SPINT

Set SDMWUP

Clear SDRMWUP

SET_FEATURE: DEVICE_REMOTE_WAKEUP

need USB resume

UPRSM = 1

AT80SND1C-ROTIL Datasheet(PDF) 96 Page - ATMEL Corporation