TLK6002 datasheet(30/96 Pages) TI

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TXAN

TXAP

TDA_[ 19: 0]

Channel A

Parallelto

Serial

TXCLK_A

Channel A

RXAP

RXAN

RDA_[ 19: 0]

Serialto

Parallel

COMMA

Detect &

8B/ 10 B

Decoding

RXCLK_A

TXBN

TXBP

TDB_[ 19: 0]

Channel B

Parallelto

Serial

TXCLK_B

Channel B

RXBP

RXBN

RDB_[ 19: 0]

Serialto

Parallel

COMMA

Detect &

8B/ 10 B

Decoding

RXCLK_B

TLK6002

SLLSE34 – MAY 2010

www.ti.com

Figure 2-11. TLK6002 – Serial Retime Mode of Operation

2.19 Latency Measurement Function

The TLK6002 includes a round trip latency measurement function to support CPRI and OBSAI base

station applications. The elapsed time from a comma (either encoded or unencoded) detected in the

transmit direction of a particular channel to a comma detected in the receive direction of the same channel

is measured and reported through the MDIO interface (TDA_[19:0]

→ RDA_[19:0] -or- TDB_[19:0] →

RDB_[19:0]). The function operates on one channel at a time. When 8b/10b encoding/decoding is

enabled, the following three control characters (containing commas) are monitored:

1. K28.1 (control = 1, data = 0x3C)

2. K28.5 (control = 1, data = 0xBC)

3. K28.7 (control = 1, data = 0xFC).

When 8b/10b encoding/decoding is disabled, the lower 7 bits of the Tx and Rx data stream are monitored

for either positive (7’b0011111) or negative (7’b1100000) comma characters.

Whether 8b/10b encoding/decoding is enabled or not, comma detection in the receive datapath must be

enabled (register bit 3.7).

The result of this measurement is readable through the MDIO interface through a 20-bit register. The

accuracy of the measurement is a function of the serial bit rate which the channel being measured is

operating at. The register will return a value of 0xFFFFF if the duration between transmit and receive

comma detection exceeds the depth of the counter. Only one measurement value is stored internally until

the 20-bit results counter is read. The counter will return zero in cases where a transmit comma was never

detected (indicating the results counter never began counting).

Description

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