Suspend Function - Fujitsu MB90335 Series Hardware Manual

MB90335 Series
11.4.4

Suspend Function

A USB device must have a configuration of bus power supply where power
consumption is 500μA or less in suspend status. The section covers a USB device from
its transmitting to suspend status to its entering STOP mode.
■ Suspend Processing
When the USB device core detects suspend status, SUSP of the UDCS register is set to be enabled.
The following shows an example of suspend operation:
Host PC
Device
SUSP
STP
●
Suspend processing
The USB Function determines that it detects suspend status when there is no operation for not less than 3
ms on the USB bus, and the SUSP interrupt cause in the UDCS register is set. If a USB device supports
remote wake-up, the USB Function waits another 2 ms (which blocks remote wake-up during this time
period), and set the device to stop mode.
CM44-10137-6E
Figure 11.4-12 Suspend Operation
1ms 1ms
3ms
SOF SOF SOF
FUJITSU MICROELECTRONICS LIMITED
CHAPTER 11 USB FUNCTION
11.4 Operation Explanation of USB Function
Suspend state
Remote wake-up support
2ms
SUSP flag
Soft clear
235