Description of Operation
8-24
ADSP-BF537 Blackfin Processor Hardware Reference
Transmit DMA Operation
shows the transmit DMA operation.
Transmit DMA normally works with a queue or ring of DMA descriptor
pairs.
•
Data
– The first descriptor in each pair points to a memory-read
data buffer aligned on a 32-bit boundary. The first 16-bit word
contains the length in bytes of the frame data, not including the
length word or FCS. The descriptor
XCOUNT
field should be set to 0.
•
Status
– The second descriptor points to a 4-byte status buffer
which is written via DMA at the end of the frame. The descriptor
XCOUNT
field should be set to 0, because the MAC controls the ter-
mination of the status buffer DMA. The driver software should
initialize the status words to zero in advance.
Status words written by the MAC after frame reception have the
same format as the current TX frame status register and always
have the transmit complete bit set to 1. Software can therefore
interrogate (poll) a TX frame’s status word to determine if the
Figure 8-7. Ethernet MAC Transmit DMA Operation
XXXX
Active DMA Descriptor
ActiveQueueEnd
DONE
NOT DONE
1A
DATA
DESCRIPTORS:
ActiveQueueHead
1B
2A
2B
3A
3B
END
0000
0000
NOT DONE
DATA
DATA
STATUS BUFFERS:
DATA BUFFERS:
LENGTH
LENGTH
LENGTH
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...