Altera High-Speed Development Kit, Stratix GX Edition - Manual (Page 108)

7–26 Quartus II Version 3.0 Altera Corporation
Standard Tests High-Speed Development Kit, Stratix GX Edition User Guide
The error detection and counting blocks monitor the match and data
valid signals. If the match signal goes low while data is valid, the error
flag is set and the error counter is incremented. The reset pushbutton
clears the error flag and resets the counter. The error insertion
pushbutton inverts one bit in one data channel for one clock cycle, which
is enough to trigger the error detection circuit.
Stratix GX SFP XCVR
This section describes the Stratix GX SFP XCVR test. Refer to “Gigabit
Transceivers with SFP Interface (Stratix GX SFP XCVR)” on page 5–19 for
information on how to perform the test.
Stratix GX SFP XCVR Test Overview
This design consists of a PLL, a 4 channel Altera GXB
transmitter/receiver block and a Verilog HDL block with the logic
required to generate a PRBS and verify that it was received correctly. The
design requires an SFP module qualified to 2.488 Gbps with an optical
fiber loopback or a SFP loopback card to complete the signal loopback.
f
For more information on the operation and parameterization of the GXB
megafunction, refer to Quartus II Help.
The top-level BDF lets you easily modify the system clock rate as desired
to evaluate a particular system configuration. The GXB megafunction
parameters are set to run at 2.488 Gbps per channel data rate compatible
with OC-48. The design has a Verilog HDL wrapper to name and place all
of the pins and to provide proper termination for the signals. The
Stratix GX pushbutton switches control the start and stop of the data
transmission and reset the circuit. The LEDs indicate the start of
transmission, the start of reception of the valid data, confirm that data
was received correctly, and indicate the reset condition.
The main system clock (parallel data rate) is derived from the
155.52-MHz crystal oscillator using the GXB megafunction clock output.
The data is generated in 16-bit words per channel using a PRBS generator
with a repetition count of 31, which results in a serial data rate of
2.488 Gbps. The data is then sent to a 4 channel version of the Altera GXB
megafunction, which converts the data into gigabit serial data streams.
The megafunction uses the basic protocol option.
The loopback card feeds the serial data back to the receive inputs on the
Stratix GX device. The data is converted back into parallel by the GXB
megafunction. Because the design uses the GXB megafunction’s double
word feature, the byte alignment of the received data can be incorrect. To
adjust it, the data is sent through a byte swap block based on