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Description of Operation
8-26
ADSP-BF537 Blackfin Processor Hardware Reference
then the MAC issues a restart command to the DMA controller to
repeat the DMA of the current descriptor’s data buffer (if enabled
by the
LCTRE
bit).
•
End of frame
– At the end of the frame, the MAC issues a finish
command to the DMA controller, causing it to advance to the next
(status) descriptor. If the TX frame exceeds the maximum length
limit (1560 bytes, or 0x618), the frame’s DMA transfer is trun-
cated. Only 1543 (0x607) are transmitted on the MII.
•
Status
– The MAC transfers the frame status into the status buffer.
•
Interrupt
– Upon completion, the DMA may issue an interrupt, if
the descriptor was programmed to do so. The DMA then advances
to the next (data) descriptor, if any.
shows an alternative descriptor structure. The frame length
value and Ethernet MAC header are separated from the data payload in
each frame.
Figure 8-8. Alternative Descriptor Structure
STATUS
FRAME 1
FRAME 2
ETHERNET
HEADER
DESCRIPTORS:
DATA
BUFFERS:
LENGTH
STATUS
ETHERNET
HEADER
DATA
LENGTH
XCOUNT
= 4
XCOUNT
= 4
XCOUNT
= 0
XCOUNT
= 0
XCOUNT
= 0
XCOUNT
= 0
16 BYTES
16 BYTES
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 ...
Страница 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
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 ...