8b/10b reset condition, Figure 5–18 – Altera Stratix GX Transceiver User Manual
Page 134
5–22
Altera Corporation
Stratix GX Transceiver User Guide
January 2005
XAUI Mode Transmitter Architecture
Figure 5–18. 8B/10B Conversion Format
8B/10B Reset Condition
The txdigitalreset controls the reset of the 8B/10B encoder. To reset
the 8B/10B encoder, txdigitalreset must be high. During reset, the
running disparity registers are cleared, along with the data registers.
Also, the 8B/10B encoder outputs a K28.5 pattern from the RD- column
continuously until txdigitalreset goes low. The tx_in[] and
tx_ctrlenable[]
are ignored during the reset state. Once out of reset,
the 8B/10B encoder starts with a bias towards negative disparity (RD-)
and transmits three K28.5 codes for synchronizing before it starts
encoding and transmitting the data on tx_in[].
If the reset for the 8B/10B encoder is asserted, the 8B/10B decoder
receiving the data may receive an invalid code error, sync error, control
detect, and/or disparity error while txdigitalreset is high.
shows the reset behavior of the 8B/10B encoder. When in
reset (txdigitalreset is high) a K28.5- (K28.5 10-bit code from the RD-
column) is sent continuously until txdigitalreset goes low. Because
of pipelining of the transmitter channel, there are several don’t-care
values (10'hxxx) until the first of three K28.5 is sent (
shows
three don’t-cares). Normal user data follows the third K28.5.
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
+ CTRL