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PXA300 Processor and PXA310 Processor
Vol. I: System and Timer Configuration Developers Manual
Doc. No. MV-TBD-00 Rev. A
CONFIDENTIAL
Copyright © 12/13/06 Marvell
Page 306
Document Classification: Proprietary Information
December 13, 2006
Not approved by Document Control. For review only.
— End of Packet (EOP) — the peripheral receives its last data sample from an external CODEC and
detects an EOP based on its receive protocol. Any remaining data samples in the peripheral receive
FIFO are treated as trailing bytes. The peripheral can be programmed to initiate a DMA request, even if
it has fewer bytes than its receive trigger threshold. The DMA responds to this request and reads out the
trailing bytes. CPU intervention is not required as long as the descriptor chain has not ended.
— Time Out (TO) — peripherals that do not support EOP protocols use a time-out mechanism to
determine if they have received their last data sample. Refer to the peripheral chapters for details of the
time out implementation. Any remaining data samples in the peripheral receive FIFO are treated as
trailing bytes. The peripheral can be programmed to initiate a DMA request, even if it has fewer bytes
than its receive trigger threshold. The DMA responds to the DMA request and reads out the trailing
bytes. CPU intervention is not required as long as the descriptor chain has not ended.
Note:
When a peripheral signals either an EOP or a TO from an external device, the DMAC sets the
end-of-receive (EOR) status bit in the corresponding channel Control Status register (DCSRx).
See
for details.
— End-of-descriptor chain (EOC) — indicates that a DMA channel is at the end of its last descriptor. After
the current transfer, DCMDx[LEN]=0 and DDADRx[STOP] = 1. DMA signals the peripheral on an
EOC and the peripheral interrupts the CPU to retrieve any trailing bytes. Refer to the individual
peripheral chapters for details on the processor interrupt implementation. EOC is the only trailing-bytes
case that requires programmed
I/O to retrieve data.
— Request-after-channel-stops (RAS) — status bit in the DMAC Control Status register (DCSRx). This bit
is set when a peripheral asserts a DMA request after the channel to which the peripheral is mapped has
stopped. See
for details.
The following cases illustrate the handling of various trailing bytes using EOR, EOC, and RAS.
Case 1 — the peripheral signals a DMA request to service trailing bytes in its receive FIFO (RxFIFO). The current
descriptor DCMDx[LEN] is equal to or greater than the trailing-bytes count.
1. The peripheral signals a receive DMA request.
2. The DMAC responds and reads out all trailing bytes including the last byte.
3. The peripheral signals an EOR.
4. The DMAC transfers all trailing bytes to the channel target and then updates DCSRx[EORINT].
5. The DMA channel can be configured to stop, jump, or just wait for another request after receiving EOR,
depending on DCSRx[EORSTOPEN] and DCSRx[EORJMPEN]. The EORINT bit must be cleared before
restarting a channel.
6. DCSRx[EORINT] set indicates that all trailing bytes were read and transferred to the required target.
Case 2 — the peripheral signals a DMA request to signal an EOR only (RxFIFO is empty). The current
descriptor DCMDx[LEN] is greater than zero.
1. The peripheral signals a receive DMA request.
2. The peripheral responds to the DMAC that the RxFIFO is empty, and the DMAC does not read any data
from the RxFIFO.
3. The peripheral signals an EOR.