EP4CE30F29C7N Datasheet, PDF (288/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

1–8
Chapter 1: Cyclone IV Transceivers Architecture
Transmitter Channel Datapath
at time n + 2 is encoded as a positive disparity code group. In the same example, the
current running disparity at time n + 5 indicates that the K28.5 in time n + 6 should be
encoded with a positive disparity. Because tx_forcedisp is high at time n + 6, and
tx_dispval is high, the K28.5 at time n + 6 is encoded as a negative disparity code
group.
Miscellaneous Transmitter PCS Features
The transmitter PCS supports the following additional features:
■ Polarity inversion—corrects accidentally swapped positive and negative signals
from the serial differential link during board layout by inverting the polarity of
each bit. An optional tx_invpolarity port is available to dynamically invert the
polarity of every bit of the 8-bit or 10-bit input data to the serializer in the
transmitter datapath. Figure 1–9 shows the transmitter polarity inversion feature.
Figure 1–9. Transmitter Polarity Inversion
Output from transmitter PCS
Converted data output to the
transmitter serializer
0 MSB
1 MSB
1
0
1
0
1
0
tx_invpolarity = HIGH
0
1
0
1
0
1
1
0
0
1
0 LSB
1 LSB
1 tx_invpolarity is a dynamic signal and might cause initial disparity errors
at the receiver of an 8B/10B encoded link. The downstream system must be
able to tolerate these disparity errors.
Cyclone IV Device Handbook,
Volume 2
October 2013 Altera Corporation