Reset – Altera Stratix GX Transceiver User Manual
Page 172
6–18
Altera Corporation
Stratix GX Transceiver User Guide
January 2005
GigE Mode Transmitter Architecture
Figure 6–18. 8B/10B Conversion Format
Reset
After power up or reset, the 8B/10B encoder in GigE mode sends three
/K28.5/
commas before user data can be sent. These commas affect the
synchronization-ordered set transmission.
After reset (txdigitalreset), three /K28.5/ commas are sent
automatically by the 8B/10B encoder. Depending on when you start
outputting the synchronization sequence, there are an even or odd
number of /Dx.y/ code groups sent by the transmitter before the
synchronization sequence. The last of three automatically sent /K28.5/
commas and the first user-sent /Dx.y/ code groups are considered as
one idle ordered set. This fact can be a problem if there are even numbers
of /Dx.y/ code groups transmitted before the start of the
synchronization sequence.
shows an example of an even number of /Dx.y/ code groups
between the last automatically sent /K28.5/ comma and the first user
sent /K28.5/. The first user-sent ordered set is ignored, so three
additional ordered sets are required for proper synchronization.
Although one set of invalid data is shown between the
txdigitalreset
signal going low and the first of three automatic
K28.5, there can be more than one invalid data set.
7
6
5
4
3
2
1
0
H
G
F
E
D
C
B
A
8b-10b conversion
7
6
5
4
3
2
1
0
9
8
g
f
i
e
d
c
b
a
j
h
LSB sent
first
MSB sent
last