Manual

858
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
– Size of buffer to send: size of the buffer to be sent to the host.
– END_B_EN: The endpoint can validate the packet (according to the values
programmed in the AUTO_VALID and SHRT_PCKT fields of UDPHS_EPTCTLx.)
(See “UDPHS Endpoint Control Register” on page 893 and Figure 44-11. Autovalid
with DMA)
– END_BUFFIT: generate an interrupt when the BUFF_COUNT in
UDPHS_DMASTATUSx reaches 0.
– CHANN_ENB: Run and stop at end of buffer
The auto-valid-bank mechanism allows the transfer of data (IN & OUT) without the intervention
of the CPU. This means that bank validation (set TX_PK_RDY or clear the RX_BK_RDY bit) is
done by hardware.
A transfer descriptor can be used. Instead of programming the register directly, a descriptor
should be programmed and the address of this descriptor is then given to
UDPHS_DMANXTDSC to be processed after setting the LDNXT_DSC field (Load Next Descrip-
tor Now) in UDPHS_DMACONTROLx register.
The structure that defines this transfer descriptor must be aligned.
Each buffer to be transferred must be described by a DMA Transfer descriptor (see “UDPHS
DMA Channel Transfer Descriptor” on page 904). Transfer descriptors are chained. Before exe-
cuting transfer of the buffer, the UDPHS may fetch a new transfer descriptor from the memory
address pointed by the UDPHS_DMANXTDSCx register. Once the transfer is complete, the
transfer status is updated in the UDPHS_DMASTATUSx register.
To chain a new transfer descriptor with the current DMA transfer, the DMA channel must be
stopped. To do so, INTDIS_DMA and TX_BK_RDY may be set in the UDPHS_EPTCTLENBx
register. It is also possible for the application to wait for the completion of all transfers. In this
case the LDNXT_DSC field in the last transfer descriptor UDPHS_DMACONTROLx register
must be set to 0 and CHANN_ENB set to 1.
Then the application can chain a new transfer descriptor.
The INTDIS_DMA can be used to stop the current DMA transfer if an enabled interrupt is trig-
gered. This can be used to stop DMA transfers in case of errors.
The application can be notified at the end of any buffer transfer (ENB_BUFFIT bit in the
UDPHS_DMACONTROLx register).