Aurora 64B/66B Frames - 13.0 English - PG074

All Aurora 64B/66B data is sent as part of a data block or a separator block. A separator block (SEP) consists of a count field indicating how many bytes are valid in that particular block. In framing, each frame begins with data blocks and ends with a separator block containing the last bytes of the frame. Idle blocks are inserted whenever data is not available. Blocks are eight bytes of scrambled data or control information with a two-bit control header (a total of 66 bits).

The following table shows a typical Aurora 64B/66B frame with an even number of data bytes.

To transmit the data, the user application configures the control signals causing the core to perform these steps:

1. Accept data from the user application on the s_axi_tx_tdata bus.
2. Indicate the end of the frame when s_axi_tx_tlast is asserted along with s_axi_tx_tkeep and stripe data across lanes in the Aurora 64B/66B channel.
3. Assembles data for presentation to the user application on the m_axi_rx_tdata bus including providing the number of valid bytes on m_axi_rx_tkeep and asserts m_axi_rx_tvalid during the m_axi_rx_tlast cycle.

When the core receives data, it performs these steps:

1. Detects and discards control bytes (idles, clock compensation).
2. Recovers data from the lanes.
3. Assembles data for presentation to the user application on the m_axi_rx_tdata bus including providing the number of valid bytes on m_axi_rx_tkeep and asserts m_axi_rx_tvalid during the m_axi_rx_tlast cycle.

Data striping is handled differently for line-rates above 16.375 Gb/s. See the following table for this packet format. Specifically, on the last cycle of a frame, all the lanes contain data blocks. Some of these blocks can be empty or half full. On the next cycle, all the lanes transmit a SEP block, each one containing the number of valid bytes transmitted in the previous cycle in that lane. When using CRC, these SEP blocks also contain the 32-bit CRC for that lane over the duration of the recent frame.