EP4CE30F29C7N Datasheet, PDF (286/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

1–6
Chapter 1: Cyclone IV Transceivers Architecture
Transmitter Channel Datapath
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 Figure 1–5.
f The encoder is compliant with Clause 36 of the IEEE 802.3 Specification.
Figure 1–5. 8B/10B Encoder Block Diagram
8
tx_ctrlenable
tx_forcedisp
tx_dispval
10
8B/10B Encoder
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). Figure 1–6 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.
Figure 1–6. Control and Data Word Encoding with the 8B/10B Encoder
clock
tx_datain[7..0]
83
78
BC
BC
0F
00
BF
3C
tx_ctrlenable
code group D3.4 D24.3 D28.5 K28.5 D15.0 D0.0 D31.5 D28.1
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.
Cyclone IV Device Handbook,
Volume 2
October 2013 Altera Corporation