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Ixiasoft
Visible to Intel only — GUID: nik1409855273056
Ixiasoft
1.3.2.1.3. Word Aligner in Bit-Slip Mode
In bit-slip mode, the word aligner is controlled by the rx_bitslip bit of the pcs8g_rx_wa_control register. At every 0-1 transition of the rx_bitslip bit of the pcs8g_rx_wa_control register, the bit-slip circuitry slips one bit into the received data stream, effectively shifting the word boundary by one bit. Also in bit-slip mode, the word aligner pcs8g_rx_wa_status register bit for rx_patterndetect is driven high for one parallel clock cycle when the received data after bit-slipping matches the 16-bit word alignment pattern programmed.
To achieve word alignment, you can implement a bit-slip controller in the FPGA fabric that monitors the rx_parallel_data signal, the rx_patterndetect signal, or both, and controls them with the rx_bitslip signal.
PCS Mode | PMA–PCS Interface Width (bits) | Word Alignment Operation |
---|---|---|
Single Width | 8 |
|
10 | ||
Double Width | 16 | |
20 |
For this example, consider that 8'b11110000 is received back-to-back and 16'b0000111100011110 is the predefined word alignment pattern. A rising edge on the rx_std_bitslip signal at time n + 1 slips a single bit 0 at the MSB position, forcing the rx_parallel_data to 8'b01111000. Another rising edge on the rx_std_bitslip signal at time n + 5 forces rx_parallel_data to 8'b00111100. Another rising edge on the rx_std_bitslip signal at time n + 9 forces rx_parallel_data to 8'b00011110. Another rising edge on the rx_std_bitslip signal at time n + 13 forces the rx_parallel_data to 8'b00001111. At this instance, rx_parallel_data in cycles n + 12 and n + 13 is 8'b00011110 and 8'b00001111, respectively, which matches the specified 16-bit alignment pattern 16'b0000111100011110.