TLK10031 Datasheet, PDF (24/146 Pages) Texas Instruments – TLK10031 Single-Channel XAUI/10GBASE-KR Transceiver

TLK10031
SLLSEL3A – JULY 2015 – REVISED AUGUST 2015
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7.3.13 Clock Tolerance Compensation (CTC)
The XAUI interface is defined to allow for separate clock domains on each side of the link. Though the
reference clocks for two devices on a XAUI link have the same specified frequencies, there can be slight
differences that, if not compensated for, will lead to over or under run of the FIFO’s on the receive/transmit
data path. The TLK10031 provides compensation for these differences in clock frequencies via the
insertion or the removal of idle (/I/) characters on all lanes, as shown in Figure 7-4 and
Figure 7-5.
Packet
IPG
Input
LANE 0 K R S D D D D ... D D D D I I I K S D
LANE 1 K R D D D D D ... D D D T I I I K D D
LANE 2 K R D D D D D ... D D D I I I I K D D
LANE 3 K R D D D D D ... D D D I I I I K D D
Output
LANE 0
LANE 1
LANE 2
LANE 3
I I S D D D D ... D D D D I I I I I S
I I D D D D D ... D D D T I I I I I D
I I D D D D D ... D D D I I I I I I D
I I D D D D D ... D D D I I I I I I D
S = Start of Packet, D = Data, T = End of Packet, I = Idle
Added Column
Figure 7-4. Clock Tolerance Compensation: Add
Packet
IPG
Input
LANE 0 K R S D D D D ... D D D D I I I K S D
LANE 1 K R D D D D D ... D D D T I I I K D D
LANE 2 K R D D D D D ... D D D I I I I K D D
LANE 3 K R D D D D D ... D D D I I I I K D D
Dropped Column
LANE 0 I I S D D D D ... D D D D I I I S D D
Output
LANE 1 I I D D D D D ... D D D T I I I D D D
LANE 2 I I D D D D D ... D D D I I I I D D D
LANE 3 I I D D D D D ... D D D I I I I D D D
S = Start of Packet, D = Data, T = End of Packet, I = Idle
Figure 7-5. Clock Tolerance Compensation: Drop
The TLK10031 allows for provisioning of both the CTC FIFO depth and the low/high watermark thresholds
that trigger idle insertion/deletion beyond the standard requirements. This allows for optimization between
maximum clock tolerance and packet length. For more information on the TLK10031 CTC provisioning,
see Section 7.4.20.
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