Intel PCI User Manual
198
Software Developer’s Manual
PHY Functionality and Features
11.11.3.4
Spectral Shaper
This function causes the 4DPAM5 waveform to have a spectral signature that is very close to that
of the MLT3 waveform used by 100BASE-TX. This enables 1000BASE-T to take advantage of
infrastructure (cables, magnetics) designed for 100BASE-TX.
The shaper works by transmitting 75% of a 4DPAM5 code in the current baud period, and adding
the remaining 25% into the next baud period.
the remaining 25% into the next baud period.
11.11.3.5
Low-Pass Filter
To aid with EMI, this filter attenuates signal components more than 180 Mhz. In 1000BASE-T, the
fundamental symbol rate is 125 Mhz.
fundamental symbol rate is 125 Mhz.
11.11.3.6
Line Driver
The line driver drives the 4DPAM5 waveforms onto the four twisted-pair channels (A, B, C, D),
adding them onto the waveforms that are simultaneously being received from the link partner.
adding them onto the waveforms that are simultaneously being received from the link partner.
11.11.3.7
Transmit/Receive Flow
Scrambler Polynomials:
1 + x
13
+ x
33
(Master PHY Mode)
1 + x
20
+ x
33
(Slave PHY Mode)
Figure 11-4. 1000BASE-T Transmit Flow And Line Coding Scheme
D0
D1
D2
D3
D4
D5
D6
D7
Scrambler
Trellis
Encoder
4D
PAM-5
PAM-5
Encoded Output
to 4-Pair UPT Line
8
9