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Preliminary Spec. ver
1.4
KS8910 100/10 Mbps ETHERNET TRANSCEIVER
100 BASE-TX DIGITAL BLOCK
A functional description of the 100Base-TX digital blocks in the 10/100 Mbit/s Transceiver is provided in this
section. Shown in Figure 3-2 is the functional blocks of 100Base-TX digital architecture.
4
M
I
I
4B/5B
The symbol encoder converts 4-bit (4B) nibble data generated by the MAC into 5-bit (5B) symbols for transmission.
This conversion is required to allow control symbols to be combined with data symbols.
The symbol encoder substitutes the first 8 bits of the MAC preamble with a J/K symbol pair (11000 10001). The
symbol encoder continues to replace subsequent 4B codes with corresponding 5B symbols. At the end of the
transmit data packet, the symbol encoder injects the T/R symbol pair indicating end of frame.
The symbol encoder continuously injects IDLE symbols into the transmit data stream until the next transmit data
packet is detected.
Parallel to Serial Block
The Parallel to Serial Block performs Serialization of code-groups for transmission on the underlying serial Physical
Medium attachment sublayer.
NRZI to NRZ Block
The NRZI to NRZ Block formats NRZI data to NRZ format for descrambling. With the receive data in NRZ format,
the descrambler can properly synchronize with the scrambled data.
5
4B/5B
Carrier
Sense
4
5
5B/4B
Figure 3-2. 100Base-TX Digital Bolck of KS8910
1
P ¡ æ S
Link
Monitor
1
P ¡ ç S
FINCTIONAL BLOCKS
Serial
NRZI
Scrambler
Serial
NRZ
DeScrambler
3-3
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