Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet
Product codes
ATSAMD21-XPRO
744
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181C–SAM-D21_Datasheet–07/2014
First, the USB must have detected a “Suspend” state on the bus, i.e. the remote wakeup request can only be sent after
INTFLAG.SUSPEND has been set.
INTFLAG.SUSPEND has been set.
The user may then write a one to the Remote Wakeup bit in CTRLB(CTRLB.UPRSM) to send an Upstream Resume to
the host initiating the wakeup. This will automatically be done by the controller after 5 ms of inactivity on the USB bus.
the host initiating the wakeup. This will automatically be done by the controller after 5 ms of inactivity on the USB bus.
When the controller sends the Upstream Resume INTFLAG.WAKEUP is set and INTFLAG.SUSPEND is cleared.
The CTRLB.UPRSM is cleared at the end of the transmitting Upstream Resume.
In case of a rebroadcast resume initiated by the host, the End of Resume bit in INTFLAG(INTFLAG.EORSM) flag is set
when the rebroadcast resume is completed.
when the rebroadcast resume is completed.
In the case where the CTRLB.UPRSM bit is set while a host initiated downstream resume is already started, the
CTRLB.UPRSM is cleared and the upstream resume request is ignored.
CTRLB.UPRSM is cleared and the upstream resume request is ignored.
31.6.2.15 Link Power Management L1 (LPM-L1) Suspend State Entry and Exit as Device
The LPM Handshake bit in CTRLB.LPMHDSK should be configured to accept the LPM transaction.
When a LPM transaction is received on any enabled endpoint n and a handshake has been sent in response by the
controller according to CTRLB.LPMHDSK, the Device Link Power Manager (EXTREG) register is updated in the bank 0
of the addressed endpoint's descriptor. It contains information such as the Best Effort Service Latency (BESL), the
Remote Wake bit (bRemoteWake), and the Link State parameter (bLinkState).
controller according to CTRLB.LPMHDSK, the Device Link Power Manager (EXTREG) register is updated in the bank 0
of the addressed endpoint's descriptor. It contains information such as the Best Effort Service Latency (BESL), the
Remote Wake bit (bRemoteWake), and the Link State parameter (bLinkState).
If the LPM transaction was positively acknowledged (ACK handshake), USB sets the Link Power Management Interrupt
bit in INTFLAG(INTFLAG.LPMSUSP) bit which indicates that the USB transceiver is suspended, reducing power
consumption. This suspend occurs 9 microseconds after the LPM transaction according to the specification.
bit in INTFLAG(INTFLAG.LPMSUSP) bit which indicates that the USB transceiver is suspended, reducing power
consumption. This suspend occurs 9 microseconds after the LPM transaction according to the specification.
To further reduce consumption, it is recommended to stop the USB clock while the device is suspended.
The MCU can also enter in one of the available sleep modes if the wakeup time latency of the selected sleep mode
complies with the host latency constraint (see the BESL parameter in
complies with the host latency constraint (see the BESL parameter in
).
Recovering from this LPM-L1 suspend state is exactly the same as the Suspend state (see Section
) except that the remote wakeup duration initiated by USB is shorter to comply with the Link
Power Management specification.
If the LPM transaction is responded with a NYET, the Link Power Management Not Yet Interrupt Flag
INTFLAG(INTFLAG.LPMNYET) is set. This generates an interrupt if the Link Power Management Not Yet Interrupt
Enable bit in INTENCLR/SET (INTENCLR/SET.LPMNYET) is set.
INTFLAG(INTFLAG.LPMNYET) is set. This generates an interrupt if the Link Power Management Not Yet Interrupt
Enable bit in INTENCLR/SET (INTENCLR/SET.LPMNYET) is set.
If the LPM transaction is responded with a STALL or no handshake, no flag is set, and the transaction is ignored.