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Receiver Clock Select Mode

K28.5

DXX.X

DXX.X

DXX.X

K28.5

DXX.X

RBC0

RBC1

SYNC

RD(0-9)

K28.5

DXX.X

DXX.X

DXX.X

K28.5

DXX.X

RBC0

SYNC

RD(0-9)

TLK2201

TLK2201I

ETHERNET TRANSCEIVERS

SLLS420F – JUNE 2000 – REVISED SEPTEMBER 2007

There are two modes of operation for the parallel busses. 1)The 10-bit (TBI) mode and 2) 5-bit (DDR) mode.

When 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. When in the DDR mode, only a full-rate

clock is available on RBC0; refer to Table 1.

Mode Selection

MODESEL

RBCMODE

MODE

FREQUENCY (TLK2201)

FREQUENCY (TLK2201I)

0

0

TBI half-rate

100-125 MHz

120-125 MHz

0

1

TBI full-rate

100-160 MHz

120-160 MHz

1

0

DDR

100-125 MHz

120-125 MHz

1

1

DDR

100-125 MHz

120-125 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. The outputs to the protocol device, byte 0 of the received data

valid on the rising edge of RBC1. See the timing diagram shown in Figure 2.

Figure 2. Synchronous Timing Characteristics Waveforms (TBI half-rate mode)

In the normal-rate mode, only RBC0 is used and operates at full data rate (i.e., 1.25 Gbps data rate produces a

125 MHz clock). The received data is output with respect to the rising edge of RBC0. RBC1 is low in this mode.

See the timing diagram shown in Figure 3.

Figure 3. Synchronous Timing Characteristics Waveforms (TBI full-rate mode)

In the double data rate mode, the receiver presents the data on both the rising and falling edges of RBC0. RBC1

is low impedance. The data is clocked bit-0 first, and aligned to the rising edge of RBC0. See the timing diagram

shown in Figure 4.

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