Wake-Up Function - Fujitsu MB90335 Series Hardware Manual

CHAPTER 11 USB FUNCTION
11.4 Operation Explanation of USB Function
11.4.5

Wake-up Function

To shift a USB device from suspend status to wake-up status, the USB protocol
provides the following two ways:
• Remote wake-up from device
• Wake-up from host PC
The above is explained.
■ Remote Wake-up
Host PC
Device
Device
Host PC
RESUM
INT pin
A device must perform processing in the following steps:
1. Recover the device from stop mode through external interrupt.
2. RESUM of the UDCC register is set.
3. RESUM of the UDCC register is cleared.
■ Wake-up from Host
Host PC
Device
WKUP
STP
For the devices, the following processing is required:
1. Set oscillation stabilizing time to be not more than 10 ms.
2. Enter an interrupt due to the WKUP factor and clear WKUP of UDCS that is the interrupt cause and
return from the interrupt.
236
Figure 11.4-13 Remote Wake-up Operation
Suspend state
Oscillation
stabilization time
STP
External interrupt
Figure 11.4-14 Wake-up Operation from Host
Suspend state
FUJITSU MICROELECTRONICS LIMITED
20ms
RESUME
RESUME
10ms
RESUM
Soft set, clear
not less than 20ms
RESUME
Oscillation
stabilization time
MB90335 Series
1ms 1ms
SOF
SOF
1ms 1ms
SOF SOF
WKUP flag
Soft clear
CM44-10137-6E