TLK10232 datasheet(14/102 Pages) TI

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TLK10232

SLLSEE1 – MAY 2013

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3.8

64B/66B Decoder/Descrambler

The data received from the serial 10GBASE-KR is 64B/66B-encoded data. The TLK10232 decodes the

data received using the 64B/66B decoding algorithm defined in the IEEE 802.3-2008 standard. The

TLK10232 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.

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.

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.

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.

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/).

TLK10232 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).

10GBASE-KR MODE FUNCTIONAL DESCRIPTION

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