TLK2226_09 Datasheet, PDF (16/52 Pages) Texas Instruments – 6 PORT GIGABIT ETHERNET TRANSCEIVER

TLK2226
SLLS689D – JANUARY 2006 – REVISED DECEMBER 2006
www.ti.com
RGMII MODE
In RGMII mode, the transmit data bus for each channel accepts 4-bit wide un-coded parallel data plus the two
GMII control bits TX_EN and TX_ER (on bit4 of TDx[4:0]). Data is sampled on the rising and falling edge of the
transmit clock. The data is first aligned to the reference clock (REFCLK), then 8B/10B encoded and passed to
the serializer. The receive data bus for each channel outputs un-coded 4-bit wide parallel data plus the two GMII
status bits RX_DV and RX_ER (on bit4 of RDx[4:0]).
RX RGMII A
TX RGMII A
TX RGMII B
RX RGMII B
5bit DDR
to
10bit
SDR
Interface
5bit DDR
to
10bit
SDR
Interface
PCS
Logic
PCS
Logic
CTC
Decode
Encode
Encode
Decode
CTC
channel A
TX Analog
Core
channel B
2 of the 6 channels of TLK2226 shown
data path for RGMII mode
Figure 15. RGMII Mode Block Diagram
RX Analog
Core
channel A
channel B
+
TXA_{_}
+
_^RXA
+
RXB
_
+
TXB_{_}
In RGMII mode, all of the PCS functions are implemented as required by the IEEE802.3 specification, including
the 8b/10b encoding, decoding, Clock Tolerance Compensation, insertion of the Start of Frame and End of
Frame codes, and the auto-negotiation state machine. In RGMII mode, it is also possible to bypass the CTC
FIFOs in which case the received data will be output with a recovered byte clock that remains in the clock
domain of the received serial data stream.
SERIAL REPEATER MODE (WITHOUT CTC)
The serial repeater mode operation can be selected on a per channel basis. The serial inputs on one channel
are transmitted back out serially on the adjacent channel. Channel A receive data is repeated out on channel B
transmit while channel B receive data is repeated out on channel A transmit. In this manner channels A and B
can form a full-duplex repeater. Likewise, channels C and D, and E and F can be used to form full-duplex
repeaters.
Repeater mode for channels A and B can be chosen separately, if desired. That is, serial data received on
channel A can be repeated out on channel B transmit pins without also choosing to repeat channel B serial
receive data out on channel A. In fact, the repeater mode selection bit for a given channel may be thought of as
simply selecting whether the data to be transmitted for that port comes from the parallel port for that channel or
the serial data from the adjacent channel. In this way, a channel may be used as a normal RGMII or RTBI
channel while the incoming serial data is also repeated out on the adjacent channel. When repeater mode for a
given channel is selected, any data presented to the parallel transmit bus for that channel will be ignored.
While in repeater mode, the incoming serial data will still go through the deserializer function, and the PCS
functions if enabled, and the deserialized data will still be presented out on the parallel transmit bus. Since the
Clock Tolerance compensation functions are disabled in this mode, the data presented on the parallel port will
reflect the CTC function being disabled as well.
Repeater mode without CTC is chosen by setting the repeater mode register bit active while also setting the
CTC_EN register bit inactive at the same time.
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