HC4GX15 Datasheet, PDF (305/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 1: HardCopy IV GX Transceiver Architecture
1–41
Transmitter Channel Datapath
Single-Width Mode
Figure 1–25 shows the 8B/10B encoder in single-width mode.
Figure 1–25. 8B/10B Encoder in Single-Width Mode
From the Byte
Serializer
datain[7:0]
control_code
tx_forcedisp
tx_dispval
8B/10B Encoder
To the Serializer
dataout[9:0]
In single-width mode, the 8B/10B encoder translates the 8-bit data to a 10-bit code
group (control word or data word) with proper disparity. If the control_code input
is high, the 8B/10B encoder translates the input data[7:0] to a 10-bit control word.
If the control_code input is low, the 8B/10B encoder translates the input
data[7:0] to a 10-bit data word.
You can use the tx_forcedisp and tx_dispval ports to control the running
disparity of the generated output data. For more information, refer to “Controlling
Running Disparity” on page 1–45.
Figure 1–26 shows the conversion format. The LSB is transmitted first.
Figure 1–26. 8B/10B Conversion Format
76543210
HGF E DCB A
control_code
8B/10B Conversion
j hgf i edcba
9876543210
MSB
LSB
Control Code Encoding
The ALTGX MegaWizard Plug-In Manager provides the tx_ctrlenable port to
indicate whether the 8-bit data at the tx_datain port should be encoded as a control
word (Kx.y). When tx_ctrlenable is low, the 8B/10B encoder block encodes the
byte at the tx_datain port (the user-input port) as data (Dx.y). When
tx_ctrlenable is high, the 8B/10B encoder encodes the input data as a Kx.y code
group. The waveform in Figure 1–27 shows the second 0 × BC encoded as a control
word (K28.5). The rest of the tx_datain bytes are encoded as a data word (Dx.y).
© June 2009 Altera Corporation
HardCopy IV Device Handbook Volume 3