AT89C5122DS-RDRUM datasheet(110/208 Pages) ATMEL

110 / 208 page

110

AT83R5122, AT8xC5122/23

4202F–SCR–07/2008

Figure 58.

Example of a Suspend/Resume Management

Warning:

The core must be switched in external clock mode before disabling the PLL.

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 function. 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 5 ms. When the upstream resume is com-

pleted, 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

Note :

WUPCPU bit must be

Cleared before enabling

the PLL

Put the USB pads

in power down mode

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