ep1sgx25d Altera Corporation, ep1sgx25d Datasheet - Page 18

• Manufacturer Part Number: ep1sgx25d
• Description: Stratix Gx Device Family Data Sheet
• Manufacturer: Altera Corporation

2–8
Stratix GX Device Handbook, Volume 1
8B/10B Encoder
The 8B/10B encoder translates 8-bit wide data + 1 control enable bit into
a 10-bit encoded data. The encoded data has a maximum run length of 5.
The 8B/10B encoder can be bypassed.
process.
Figure 2–4. Encoding Process
Transmit State Machine
The transmit state machine operates in either XAUI mode or in GIGE
mode, depending on the protocol used.
GIGE Mode
In GIGE mode, the transmit state machines convert all idle ordered sets
(/K28.5/, /Dx.y/) to either /I1/ or /I2/ ordered sets. /I1/ consists
of a negative-ending disparity /K28.5/ (denoted by /K28.5/-)
followed by a neutral /D5.6/. /I2/ consists of a positive-ending
disparity /K28.5/ (denoted by /K28.5/+) and a negative-ending
disparity /D16.2/ (denoted by /D16.2/-). The transmit state machines
do not convert any of the ordered sets to match /C1/ or /C2/, which are
the configuration ordered sets. (/C1/ and /C2/ are defined by
(/K28.5/, /D21.5/) and (/K28.5/, /D2.2/), respectively.) Both the
/I1/ and /I2/ ordered sets guarantee a negative-ending disparity after
each ordered set. The GIGE transmit state machine can be statically
disabled in the Quartus II software, even if using the GIGE protocol
mode.
MSB sent last
9
j
h
8
H
7
g
7
G
6
8b-10b conversion
6
5
F
f
E
5
4
i
3
D
Figure 2–4
e
4
2
C
d
3
B
1
c
2
diagrams the encoding
0
A
LSB sent first
b
1
Altera Corporation
+
a
0
ctrl
June 2006