TLK10031 Datasheet, PDF (23/146 Pages) Texas Instruments – TLK10031 Single-Channel XAUI/10GBASE-KR Transceiver

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TLK10031
SLLSEL3A – JULY 2015 – REVISED AUGUST 2015
7.3.8 64B/66B Decoder/Descrambler
The data received from the serial 10GBASE-KR is 64B/66B-encoded data. The TLK10031 decodes the
data received using the 64B/66B decoding algorithm defined in the IEEE 802.3-2008 standard. The
TLK10031 creates consecutive 72-bit data words from the encoded 66-bit code words for transfer over the
XAUI interface to the MAC. The information for the two XAUI transfers includes 64 bits of data and 8 bits
of control information before 8B/10B encoding.
Not all 64B/66B block payloads are valid. Invalid block payloads are handled by the 64B/66B decoder
block and appropriate error handling is provided, as defined in the IEEE 802.3-2008 standard. The
decoding algorithm includes two steps: a descrambling step which descrambles 64 bits of the 66-bit code
word with the scrambling polynomial x⁵⁸+x³⁹+1, and a decoding step which converts the 66 bits of data
received into 64 bits of data and 8 bits of control information. These words are sent to the receive CTC
FIFO.
7.3.9 Transmit Gearbox
The function of the transmit gearbox is to convert the 66-bit encoded, scrambled data stream into a 16-bit-
wide data stream to be sent out to the serializer and ultimately to the physical medium attachment (PMA)
device. The gearbox is needed because while the effective bit rate of the 66-bit data stream is equal to the
effective bit rate of the 16-bit data, the clock rates of the two buses are of different frequencies.
7.3.10 Receive Gearbox
While the transmit gearbox only performs the task of converting 66-bit data to be transported on to the 16-
bit serializer, the receive gearbox has more to do than just the reverse of this function. The receive
gearbox must also determine where within the incoming data stream the boundaries of the 66-bit code
words are.
The receive gearbox has the responsibility of initially synchronizing the header field of the code words and
continuously monitoring the ongoing synchronization. After obtaining synchronization to the incoming data
stream, the gearbox assembles 66-bit code words and presents these to the 64B/66B decoder.
Note that in FEC mode, the Receive Gearbox blindly converts 16-bit data to 66-bit data and depends on
the RX FEC logic to frame align the data.
7.3.11 XAUI Lane Alignment / Code Gen (XAUI PCS)
The XAUI interface standard is defined to allow for 21 UI of skew between lanes. This block is
implemented to handle up to 30 UI (XAUI UI) of skew between lanes using /A/ characters. The state
machine follows the standard 802.3-2008 defined state machine.
7.3.12 Inter-Packet Gap (IPG) Characters
The XAUI interface transports information that consists of packets and inter-packet gap (IPG) characters.
The IEEE 802.3-2008 standard defines that the IPG, when transferred over the XAUI interface, consists of
alignment characters (/A/), control characters (/K/) and replacement characters (/R/).
TLK10031 converts all AKR characters to IDLE characters, performs insertions or deletions on the IDLE
characters, and transmits only encoded IDLE characters out to the 10GBASE-KR interface. The receive
channel expects encoded IDLE characters to enter the 10GBASE-KR interface, and performs insertions
and deletions on IDLE characters and then converts IDLE characters back to AKR characters. Any AKR
characters received on the high speed interface are by default converted to IDLE characters for
reconversion to AKR columns.
Both the transmit and receive FIFOs rely upon a valid IDLE stream to perform clock tolerance
compensation (CTC).
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