TLK105 Datasheet, PDF (24/99 Pages) Texas Instruments – Industrial Temp, Single Port 10/100Mbs Ethernet Physical Layer Transceiver

TLK105
TLK106
SLLSEB8A – AUGUST 2012 – REVISED MARCH 2013
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5 Architecture
The TLK10x Fast Ethernet transceiver is a physical layer core for Ethernet 100Base-TX and 10Base-T
applications. The TLK10x contains all the active circuitry required to implement the physical layer functions
to transmit and receive data on standard CAT 3 and 5 unshielded twisted pair. The core supports the
IEEE 802.3 Standard Fast Media Independent Interface (MII), as well as the Reduced Media Independent
Interface (RMII), for direct connection to a MAC/Switch port.
The TLK10x uses mixed signal processing to perform equalization, data recovery and error correction to
achieve robust and low power operation over the existing CAT 5 twisted pair wiring. The TLK10x
architecture not only meets the requirements of IEEE802.3, but maintains a high level of margin over the
IEEE requirements for NEXT, Alien and External noise.
4B/5B
encoding
Manchester
encoding
Scrambler
NRZ to NRZI
Convertor
MLT-3
encoding
Transmit
D/A
Convertor
100Base TX
Line Driver
10Base T
Filter
10Base T
Line Driver
MII
Adv.
Link Monitor
100Base TX
10Base-T
Manchester
decoding
Receive
4B/5B
decoding
DeScrambler
NRZI to NRZ
Convertor
MLT-3
decoding
DSP (BLW
Correction,
Adapt. Equal)
10Base T
Receive
Filter
ADC (Filter,
Amplifierl)
Figure 5-1. PHY Architecture
5.1 100Base-TX Transmit Path
In 100Base-TX, the MAC feeds the 100Mbps transmit data in 4-bit wide nibbles through the MII interface.
The data is encoded into 5-bit code groups, encapsulated with control code symbols and serialized. The
control-code symbols indicate the start and end of the frame and code other information such as transmit
errors. When no data is available from the MAC, IDLE symbols are constantly transmitted. The serialized
bit stream is fed into a scrambler. The scrambled data stream passes through an NRZI encoder and then
through an MLT3 encoder. Finally, it is fed to the DAC and transmitted through one of the twisted pairs of
the cable.
5.1.1 MII Transmit Error Code Forwarding
According to IEEE 802.3:
“If TX_EN is de-asserted on an odd nibble boundary, PHY should extend TX_EN by one TX_CLK
cycle and behave as if TX_ER were asserted during that cycle”.
The TLK10x supports Error Forwarding in MII transmission from the MAC to the PHY. Error forwarding
allows adding information to the frame to be used as an error code between the 2 MACs. The error code
informs the receiving MAC on the link partner side of the reason for the error from the transmitting side. If
the MAC transmits an odd number of nibbles, an additional error nibble is added to the transmitted frame
just before the end of the transmission.
To turn off Transmit Error Forwarding, write to bit 1 of register CR2 (0x000A). If Error Forwarding is
disabled, delivered packets contain either odd or even numbers of nibbles.
In Figure 5-2, Error Code Forwarding functionality is illustrated. The wave diagram demonstrates MAC’s
transmitted signals in one side and MAC’s reception signals on link partner side.
24
Architecture
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