Xilinx LOGICORE UG144 - Manual (Page 130)

130 www.xilinx.com 1-Gigabit Ethernet MAC v8.5 User Guide
UG144 April 24, 2009
Appendix A: Using the Client-Side FIFO R
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Overview of LocalLink Interface
Data Flow
Data is transferred on the LocalLink interface from source to destination, with the flow
being governed by the four active low control signals sof_n, eof_n, src_rdy_n, and
dst_rdy_n
. The flow of data is controlled by the src_rdy_n and dst_rdy_n signals.
Only when these signals are asserted simultaneously is data transferred from source to
destination. The individual packet boundaries are marked by the sof_n and eof_n
signals. For more information on the LocalLink interface see to Xilinx Application Note
XAPP691 , “Parameterizable LocalLink FIFO” available at
direct.xilinx.com/bvdocs/appnotes/xapp691.pdf .
Figure A-2 shows the transfer of an 8-byte frame.
Figure A-3 illustrates frame transfer of a 5-byte frame, where both the src_rdy_n and
dst_rdy_n signals are used to control the flow of data across the interface.
Figure A-2: Frame Transfer across LocalLink Interface
Figure A-3: Frame Transfer with Flow Control
clock
data[7:0]
sof_n
eof_n
src_rdy_n
dst_rdy_n
0 1 2 3 4 5 6 7
clock
data[7:0]
sof_n
eof_n
src_rdy_n
dst_rdy_n
0 1 2 3 4