Altera Cyclone IV Device Handbook page 292

1–12
The high-speed serial link can be AC- or DC-coupled, depending on the serial
protocol implementation. In an AC-coupled link, the AC-coupling capacitor blocks
the transmitter DC common mode voltage as shown in
and on-chip biasing circuitry automatically restores the common mode voltage. The
biasing circuitry is also enabled by enabling OCT. If you disable the OCT, then you
must externally terminate and bias the receiver. AC-coupled links are required for
PCIe, GbE, Serial RapidIO, SDI, XAUI, SATA, V-by-One and Display Port protocols.
Figure 1–12. AC-Coupled Link with OCT
Cyclone IV Device Handbook,
Volume 2
Transmitter
TX Termination
TX
V
CM
Chapter 1: Cyclone IV Transceivers Architecture
Figure
AC Coupling
Capacitor
Physical Medium
Physical Medium
AC Coupling
Capacitor
RX
V
CM
Receiver Channel Datapath
1–12. Receiver OCT
Receiver
RX Termination
February 2015 Altera Corporation