td(S)

td(S)

td(H)

td(H)

K28.5

DXX.X

DXX.X

DXX.X

K28.5

DXX.X

RBC0

RBC1

SYNC

RD(0–9)

td(H)

td(S)

K28.5

DXX.X

DXX.X

DXX.X

K28.5

DXX.X

RBC0

SYNC

RD(0–9)

TLK1221

SLLS713C – FEBRUARY 2007 – REVISED SEPTEMBER 2009....................................................................................................................................... www.ti.com

Data Reception

The receiver section deserializes the differential serial data. The serial data is retimed based on an interpolated

clock generated from the reference clock. The serial data is then aligned to the 10-bit word boundaries and

presented to the protocol controller along with the receive byte clocks (RBC0, RBC1).

Receiver Clock Select Mode

The TLK1221 only supports TBI-mode operation with half-rate and full-rate clocks on RBC0 and RBC1. In TBI

mode, there are two user-selectable clock modes that are controlled by the RBCMODE terminal: 1) full-rate clock

on RBC0 and 2) half-rate clocks on RBC0 and RBC1.

Table 1. Mode Selection

RECEIVE BYTE CLOCK

RBCMODE

MODE

TLK1221

0

TBI half-rate

30–65 MHz

1

TBI full-rate

60–130 MHz

In the half-rate mode, two receive byte clocks (RBC0 and RBC1) are 180 degrees out of phase and operate at

one-half the data rate. The clocks are generated by dividing down the recovered clock. The received data is

output with respect to the two receive byte clocks (RBC0, RBC1), allowing a protocol device to clock the parallel

bytes using the RBC0 and RBC1 rising edges. For the outputs to the protocol device, byte 0 of the received data

is valid on the rising edge of RBC1. Refer to the timing diagram shown in Figure 2.

Figure 2. Synchronous Timing Characteristic Waveforms (TBI Half-Rate Mode)

The receiver clock interpolator can lock to the incoming data without the need for a lock-to-reference preset. The

received serial data rate (RXP and RXN) is at the same baud rate as the transmitted data stream, ±0.02% (200

PPM) for proper operation.

Figure 3. Synchronous Timing Characteristic Waveforms (TBI Full-Rate Mode)

Receiver Word Alignment

These devices use the IEEE 802.3 Gigabit Ethernet defined 10-bit K28.5 character, which contains the 7-bit

comma-pattern word alignment scheme. The following sections explain how this scheme works and how it

realigns to the proper byte boundary of the data.

4

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