1–6
Chapter 1: Cyclone IV Transceivers Architecture
Transmitter Channel Datapath
February 2015
Altera Corporation
For example, when operating an EP4CGX150 transmitter channel at 3.125 Gbps
without byte serializer, the FPGA fabric frequency is 312.5 MHz (3.125 Gbps/10). This
implementation violates the frequency limit and is not supported. Channel operation
at 3.125 Gbps is supported when byte serializer is used, where the FPGA fabric
frequency is 156.25 MHz (3.125 Gbps/20).
The byte serializer forwards the least significant byte first, followed by the most
significant byte.
8B/10B Encoder
The optional 8B/10B encoder generates 10-bit code groups with proper disparity from
the 8-bit data and 1-bit control identifier as shown in
.
f
The encoder is compliant with Clause 36 of the
The 1-bit control identifier (
tx_ctrlenable
) port controls the 8-bit translation to either
a 10-bit data word (Dx.y) or a 10-bit control word (Kx.y).
shows the 8B/10B
encoding operation with the
tx_ctrlenable
port, where the second 8'hBC data is
encoded as a control word when
tx_ctrlenable
port is asserted, while the rest of the
data is encoded as a data word.
1
The IEEE 802.3 8B/10B encoder specification identifies only a set of 8-bit characters
for which the
tx_ctrlenable
port should be asserted. If you assert
tx_ctrlenable
port for any other set of characters, the 8B/10B encoder might encode the output 10-
bit code as an invalid code (it does not map to a valid Dx.y or Kx.y code), or an
unintended valid Dx.y code, depending on the value entered. It is possible for a
downstream 8B/10B decoder to decode an invalid control word into a valid Dx.y code
without asserting any code error flags. Altera recommends not to assert
tx_ctrlenable
port for unsupported 8-bit characters.
Figure 1–5. 8B/10B Encoder Block Diagram
Figure 1–6. Control and Data Word Encoding with the 8B/10B Encoder
tx_ctrlena
b
le
tx_forcedisp
8
B/10B Encoder
tx_dispval
10
8
tx_ctrlenable
clock
code group
D3.4
D24.3
D28.5
K28.5
D0.0
D31.5
D28.1
D15.0
tx_datain[7..0]
83
78
BC
BC
00
BF
3C
0F
Содержание Cyclone IV
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