Datasheet

stage if the USB detects a corrupted packet. The IN packet will remain stored in the bank and
PINTFLAG.TRCPT0/1 will be set.
32.6.3.15 PERR Error
This error exists for all pipes. It sets the PINTFLAG.PERR Interrupt, which triggers an interrupt if
PINTFLAG.PERR is set. The user must check the PINTSMRY register to find out the pipe which can
cause an interrupt.
A PERR error occurs if one of the error field in the STATUS_PIPE register in the Host pipe descriptor is
set and the Error Count field in STATUS_PIPE (STATUS_PIPE.ERCNT) exceeds the maximum allowed
number of Pipe error(s) as defined in Pipe Error Max Number field in CTRL_PIPE
(CTRL_PIPE.PERMAX). Refer to section 32.8.7.7 STATUS_PIPE register.
If one of the error field in the STATUS_PIPE register from the Host Pipe Descriptor is set and the
STATUS_PIPE.ERCNT is less than the CTRL_PIPE.PERMAX, the STATUS_PIPE.ERCNT is
incremented.
32.6.3.16 Link Power Management L1 (LPM-L1) Suspend State Entry and Exit as Host.
An EXTENDED LPM transaction can be transmitted by any enabled pipe. The PCFGn.PTYPE should be
set to EXTENDED. Other fields as PCFG.PTOKEN, PCFG.BK and PCKSIZE.SIZE are irrelevant in this
configuration. The user should also set the EXTREG.VARIABLE in the descriptor as described in
32.8.7.4 EXTREG register.
When the pipe is configured and enabled, an EXTENDED TOKEN followed by a LPM TOKEN are
transmitted. The device responds with a valid HANDSHAKE, corrupted HANDSHAKE or no
HANDSHAKE (TIME-OUT).
If the valid HANDSHAKE is an ACK, the host will immediately proceed to L1 SLEEP and the
PINTFLAG.TRCT0 is set. The minimum duration of the L1 SLEEP state will be the
TL1RetryAndResidency as defined in the reference document "ENGINEERING CHANGE NOTICE, USB
2.0 Link Power Management Addendum". When entering the L1 SLEEP state, the CTRLB.SOFE is
cleared, avoiding Start-of-Frame generation.
If the valid HANDSHAKE is a NYET PINTFLAG.TRFAIL is set.
If the valid HANDSHAKE is a STALL the PINTFLAG.STALL is set.
If there is no HANDSHAKE or corrupted HANDSHAKE, the EXTENDED/LPM pair of TOKENS will be
transmitted again until reaching the maximum number of retries as defined by the CTRL_PIPE.PERMAX
in the pipe descriptor.
If the last retry returns no valid HANDSHAKE, the PINTFLAGn.PERR is set, and the STATUS_BK is
updated in the pipe descriptor.
All LPM transactions, should they end up with a ACK, a NYET, a STALL or a PERR, will set the
PSTATUS.PFREEZE bit, freezing the pipe before a succeeding operation. The user should unfreeze the
pipe to start a new LPM transaction.
To exit the L1 STATE, the user initiate a DOWNSTREAM RESUME by setting the bit CTRLB.RESUME or
a L1 RESUME by setting the Send L1 Resume bit in CTRLB (CTRLB.L1RESUME). In the case of a L1
RESUME, the K STATE duration is given by the BESL bit field in the EXTREG.VARIABLE field. See
32.8.7.4 EXTREG.
When the host is in the L1 SLEEP state after a successful LPM transmitted, the device can initiate an
UPSTREAM RESUME. This will set the Upstream Resume Interrupt bit in INTFLAG (INTFLAG.UPRSM).
The host should proceed then to a L1 RESUME as described above.
SAM D21 Family
USB – Universal Serial Bus
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 811