Altera Corporation
2–205
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
Figure 2–151. Setting Duty Cycle in Classic Timing Analyzer
1
If the PLD-transceiver interface clocks are fed to an off-chip PLL
(for example, VCXO-based PLL for de-jittering purposes), you
must make sure that the PLL can tolerate the 60-40% duty cycle
on its input reference clock.
Loopback Modes
There are several loopback modes available on the Stratix II GX
transceiver block that allow you to isolate portions of the circuit. All paths
are designed to run up to full speed. The available loopback paths are:
■
Serial loopback available in all functional modes except PCI Express
(PIPE)
■
Reverse serial loopback available in Basic mode with 8B/10B
■
PCI Express PIPE reverse parallel loopback available in PCI Express
protocol
■
Reverse serial pre-CDR loopback available in Basic mode with
8B/10BReverse serial loopback available in Basic mode with 8B/10B
■
Parallel loopback available in Basic mode for BIST testing only
Serial Loopback
Figure 2–152
shows the data path for serial loopback. A data stream is fed
to the transmitter from the FPGA logic array and has the option of
utilizing all the blocks in the transmitter. The data, in serial form, then
traverses from the transmitter to the receiver. The serial data is the data
that is transmitted from the Stratix II GX device. Once the data enters the
receiver in serial form, it can utilize any of the receiver blocks and is then
fed into the FPGA logic array.