Visible to Intel only — GUID: fip1488565723013
Ixiasoft
Visible to Intel only — GUID: fip1488565723013
Ixiasoft
51.3.4. Transmit Elastic Buffer
Transmit elastic buffer is asynchronous FIFO with fix high and low watermark level. High watermark level is fixed at (TX_BUFFER_DEPTH/2 + 4) valid entries and low watermark level is fixed at (TX_BUFFER_DEPTH/2 - 4) valid entries. When the number of valid entries is equal or above the high watermark level, any IDLE symbol appearing at the write port of the buffer is dropped (IDLE symbol deletion). When the number of valid entries is equal or below low watermarks level, any IDLE symbol read from the read port does not increment the read pointer of the buffer (IDLE symbol insertion). IDLE symbol definition is tx_en = 0 and tx_err = 0.
The buffer depth is fixed at 64. Higher buffer depths provides more margins to avoid overflow/underflow condition to occur. The buffer depth configuration depends on the maximum Ethernet packet or maximum IDLE symbol separation in the Ethernet protocol and the maximum ppm different between the two clock sources.