DP83865-EB National Semiconductor, DP83865-EB Datasheet - Page 51

• Manufacturer Part Number: DP83865-EB
• Description: BOARD EVALUATION DP83865
• Manufacturer: National Semiconductor

Specifications of DP83865-EB

• Main Purpose: Interface, Ethernet
• Utilized Ic / Part: DP83865
• Lead Free Status / RoHS Status: Not applicable / Not applicable

4.0 Functional Description
4.3.4 Baseline Wander (BLW) Correction
Baseline wander is the slow variation of the DC level of the
incoming signal due to the non-ideal electrical characteris-
tics of the magnetics and the inherent DC component of
the transmitted waveform. The BLW correction circuit uti-
lizes the slicer error signal to estimate and correct for BLW.
4.3.5 Slicer
The Slicer selects the PAM-5 symbol value (+2,+1,0,-1,-2)
closest to the voltage input value after the signal has been
corrected for line Inter Symbol Interference (ISI), attenua-
tion, echo, crosstalk and BLW.
The slicer produces an error output and symbol value deci-
sion output. The error output is the difference between the
SCRAMBLER
SIGN
3-bits/sample
PAM-5
PAM-5 w ith PR (.7 5+.2 5T)
-0.200
-0.400
0.75
PMA Transmitter Block
1.200
1.000
0.800
0.600
0.400
0.200
0.000
PARTIAL RESPONSE PULSE SHAPE CODING
Figure 4. Effect on Spectrum of PR-shaped PAM-5 coding
10.00
5-LEVEL PAM-5 TO 17-LEVEL PAM
0.75 X(k) + 0.25 X(k-1)
(Continued)
critica l reg io n -- (30 MH z -- 6 0MH z)
Z
0.25
Figure 3. PMA Transmitter Block
-1
Transmit Spectra
5-bits/sample
17-LEVEL
PAM-5
F re q ue n cy (M Hz)
51
actual voltage input and the ideal voltage level represent-
ing the symbol value. The error output is fed back to the
BLW, AGC, Crosstalk Canceller and Echo Canceller sub
blocks to be used in their respective algorithms.
4.4 1000BASE-T PCS Receiver
The PCS Receiver consists of several sub functional
blocks that convert the incoming quartet of quinary sym-
bols (PAM-5) data from the PMA Receiver A, B, C, and D to
8-bit receive data (RXD[7:0]), data valid (RX_DV), and
receive error (RX_ER) signals on the GMII. The block dia-
gram of the 1000BASE-T Functional Block in section
“ Block Diagram” on page 2 provides an overview of the
Manchester coding
LOOKUP
2-bit MLT-3
TABLE
PAM-5
20-bits/sample
CONTROL
DAC
MUX
100.00
1000
DAC
100
10
Manchester/
MLT-3/PAM-17
ANALOG
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