ST STM32F101 series Reference Manual page 629

Universal serial bus full-speed device interface (USB)
Bit 11 SUSPM: Suspend mode interrupt mask
Bit 10 RESETM: USB reset interrupt mask
Bit 9 SOFM: Start of frame interrupt mask
Bit 8 ESOFM: Expected start of frame interrupt mask
Bits 7:5 Reserved.
Bit 4 RESUME: Resume request
Bit 3 FSUSP: Force suspend
Bit 2 LP_MODE: Low-power mode
Bit 1 PDWN: Power down
Bit 0 FRES: Force USB Reset
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0: Suspend Mode Request (SUSP) Interrupt disabled.
1: SUSP Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
0: RESET Interrupt disabled.
1: RESET Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
0: SOF Interrupt disabled.
1: SOF Interrupt enabled, an interrupt request is generated when the corresponding bit in the
USB_ISTR register is set.
0: Expected Start of Frame (ESOF) Interrupt disabled.
1: ESOF Interrupt enabled, an interrupt request is generated when the corresponding bit in
the USB_ISTR register is set.
The microcontroller can set this bit to send a Resume signal to the host. It must be activated,
according to USB specifications, for no less than 1 mS and no more than 15 mS after which
the Host PC is ready to drive the resume sequence up to its end.
Software must set this bit when the SUSP interrupt is received, which is issued when no
traffic is received by the USB peripheral for 3 mS.
0: No effect.
1: Enter suspend mode. Clocks and static power dissipation in the analog transceiver are left
unaffected. If suspend power consumption is a requirement (bus-powered device), the
application software should set the LP_MODE bit after FSUSP as explained below.
This mode is used when the suspend-mode power constraints require that all static power
dissipation is avoided, except the one required to supply the external pull-up resistor. This
condition should be entered when the application is ready to stop all system clocks, or
reduce their frequency in order to meet the power consumption requirements of the USB
suspend condition. The USB activity during the suspend mode (WKUP event)
asynchronously resets this bit (it can also be reset by software).
0: No Low-power mode.
1: Enter Low-power mode.
This bit is used to completely switch off all USB-related analog parts if it is required to
completely disable the USB peripheral for any reason. When this bit is set, the USB
peripheral is disconnected from the transceivers and it cannot be used.
0: Exit Power Down.
1: Enter Power down mode.
0: Clear USB reset.
1: Force a reset of the USB peripheral, exactly like a RESET signalling on the USB. The
USB peripheral is held in RESET state until software clears this bit. A "USB-RESET"
interrupt is generated, if enabled.
DocID13902 Rev 15
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