Achronix Speedster22i SerDes - Manual (Page 29)

EFIFO Operation
“Figure 15: EFIFO SKP Addition/Removal” illustrates the process of SKP addition/removal.
Figure 15: EFIFO SKP Addition/Removal
In “Figure 15: EFIFO SKP Addition/Removal” upon reset, the difference between the read
and write counters is equal to fifo_mid (half the size of the buffer; default 16).
If clk_in is operating at a lower frequency than clk_out, then the read operation is faster than
the write operation and the difference between the write and read counters will be less than
fifo_mid. In this case, to compensate for clk_in being slower, an SKP is added to the data
stream.
If clk_in is operating at a higher frequency than clk_out, then the read operation is slower
than the write operation and the difference between the write and read counters will be
greater than fifo_mid. In this case, to compensate for clk_out being slower, an SKP is
removed from the data stream.
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