3. Specifications
The MegaCore® function consists of an encoder (ENC8B10B) and a
decoder (DEC8B10B). See Figure 3–2 on page 3–3. The encoder encodes
one 8-bit byte of data into a 10-bit transmission code, and the decoder
decodes a 10-bit code into one 8-bit byte of data. Figure 3–1 illustrates the
bidirectional conversion process.
Functional
Description
The eight input bits are named A, B, C, D, E, F, G, H. Bit Ais the least
significant bit (LSB), and bit His the most significant bit (MSB). They are
split into two groups: The five-bit group A, B, C, D, E, and the three-bit
group F, G, H.
The coded bits are named a, b, c, d, e, i, f, g, h, j(the order is not
alphabetical). These bits are also split into two groups: the six-bit group
a, b, c, d, e, i, and the four-bit group f, g, h, j.
Figure 3–1. 8b10b Conversion
7
6
5
F
4
3
2
1
0
H
G
E
D
C
B
A
8b10b
Conversion
j
h
8
g
f
i
e
4
d
3
c
b
1
a
0
9
7
6
5
2
MSB sent last
LSB sent first
In bit serial transmission, the LSB is usually transmitted first, while the
MSB is usually transmitted last.
Disparity
Disparity is the difference between the number of 1s and 0s in the
encoded word.
Altera Corporation
October 2007
MegaCore Version 7.2
7.23–1
ALTERA [ ALTERA CORPORATION ]
