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Description of Operation
8-16
ADSP-BF537 Blackfin Processor Hardware Reference
Discarded Frames
Frames that fail the address filter are discarded immediately after the desti-
nation address is received, and neither their data nor their status values are
written to memory via DMA. Frames that pass the address filter but fail
the frame filter before 32 bytes are received are also discarded immedi-
ately. Once at least 32 bytes of a frame have been received, and if the
address and frame filters both pass, the MAC begins to write the frame to
memory via DMA RX.
Aborted Frames
Frames that fail the frame filter after 32 bytes have been received are
aborted. The MAC issues a restart DMA control command, causing the
current RX data DMA descriptor to be reinitialized with its starting
address and counts. The aborted frame’s status is not written to memory.
Instead, the current DMA data and status buffers are recycled for the next
RX frame. For all frames that pass both the address and frame filters, both
data and status are written to memory via DMA.
Control Frames
If the
FLCE
(flow control enable) bit is set, MAC control frames (with the
control type 88-08) whose DAs match either the station MAC address
(with inverse filtering disabled) or the global pause multicast address will
pass the address filter, and thus may also have status of receiveOK. If the
frame also is a supported pause control frame (with length = 64 bytes, and
opcode = pause = 00-01, and in full-duplex mode), then the frame filter
condition is determined by the
PCF
(pass control frames) bit. If the frame
is not also a supported pause control frame, then it is in error, and its
frame filter condition depends on the
PBF
(pass bad frames) bit.
Examples
• To perform standard IEEE-802.3 filtering, clear the operating
mode register bits
HU
,
PR
,
IFE
,
DBF
,
PBF
, and
PSF
. With these selec-
tions, the Ethernet MAC accepts error-free broadcast frames and
Содержание Blackfin ADSP-BF537
Страница 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...