Transceivers
8B/10B Encoder
The 8B/10B encoder block is used in all supported functional modes. The
8B/10B encoder block takes in 8-bit data from the byte serializer or the
transmitter phase compensation FIFO buffer. It generates a 10-bit code
group with proper running disparity from the 8-bit character and a 1-bit
control identifier (tx_ctrlenable). When tx_ctrlenableis low, the
8-bit character is encoded as data code group (Dx.y). When
tx_ctrlenableis high, the 8-bit character is encoded as a control code
group (Kx.y). The 10-bit code group is fed to the serializer. The 8B/10B
encoder conforms to the IEEE 802.3 1998 edition standard.
Figure 2–6 shows the 8B/10B conversion format.
f
For additional information regarding 8B/10B encoding rules, refer to the
Specifications and Additional Information chapter in volume 2 of the
Arria GX Device Handbook.
Figure 2–6. 8B/10B Encoder
7
6
5
F
4
3
2
1
0
Ctrl
H
G
E
D
C
B
A
8B-10B Conversion
j
h
g
f
i
e
4
d
3
c
b
a
0
9
8
7
6
5
2
1
MSB
LSB
During reset (tx_digitalreset), the running disparity and data
registers are cleared and the 8B/10B encoder outputs a K28.5 pattern
from the RD- column continuously. Once out of reset, the 8B/10B encoder
starts with a negative disparity (RD-) and transmits three K28.5 code
groups for synchronizing before it starts encoding the input data or
control character.
Transmit State Machine
The transmit state machine operates in either PCI Express (PIPE) mode,
XAUI mode, or GIGE mode, depending on the protocol used.
2–8
Arria GX Device Handbook, Volume 1
Altera Corporation
May 2008
ALTERA [ ALTERA CORPORATION ]
