1.3.2 64b66b/64b67b

The 64b66b/64b67b (64b6xb) interface modes are used mainly for 10 Gbps-based protocols, 10G base interface over Ethernet (10GBASE-R/KR), common public radio interface (CPRI) rates of 9.830 Gbps, and 40GBASE-R standards. The 64b/66b encoder is used to achieve DC balance and sufficient data transitions for clock recovery. It encodes 64-bit XGMII data and 8-bit XGMII control into 10GBASE-R 
66-bit control or data blocks in accordance with Clause 49 of the IEEE802.3-2008 specification.

The following features are supported in the 64b6xb:

  • Fabric width is selectable. Four and eight byte widths are available.
  • Gearbox functions are set for 67-bit or 66-bit block size. The gearbox functions can be bypassed.
  • Optional scrambler and descrambler 64b66b data.
  • Optional test pattern generate/compare mode.
  • Optional PRBS generate/compare mode.
  • Optional disparity generate/check (applies to 64b67b data).
  • Receiver block lock state-machine controlling the hunt for synchronization header boundaries is available in two forms.
    • The IEEE 802.3 Clause 49 state-machine loses lock when 16 invalid headers are observed within a contiguous set of 64 headers.
    • The IEEE 802.3 Clause 82 state-machine loses lock when 65 invalid headers are observed within a contiguous set of 1024 headers. 
Both block lock state-machines require an initial set of 64 contiguous valid headers to gain block lock. The Clause 82 state-machine is specified for use with 40 G and 100 G links. One of these state-machines must be enabled in order for the receiver to locate and lock onto the block boundaries.
  • Optional receiver IEEE 802.3 bit error rate monitor function.
  • Optional data path delay status monitors for transmit and receive.
Note: Forward Error Correction (FEC) option of IEEE 802.3 10GBASE-KR is not supported by the 64b6xb PCS.

The encoder uses per-lane block interfaces with a fabric interface to receive and transmit encoded data and a PMA interface to send parallel data to the transceiver. This mode also supports the Interlaken protocol by providing 64b67b with optional embedded gearing logic.