Step 4: Results

Qualification of simulation results is based on the eye-height, eye-width, and BER curves. Check the eye-height and eye-width at target BER of 10e-12. These results are found in the report generated by the simulation tool. For example, the Sigrity tool gives the following information at RX:

At BER of 10e-12, running at 5 Gbps bit rate

The eye-width is 0.68 UI (Unit Interval)
The eye-height is 213 mV

This simulation is on the SmartFusion2 Development Kit using the Sigrity tool and the waveforms are shown in the following figure. The simulation result shows that it meets the PCIe 2.0 requirements.

Figure 1. Expected Results from Simulations (Eye Diagram, Eye Contour, and Bath Tub Curve)

The following table lists the specifications of the received signal for PCIe.

Table 1. Specifications of the Received Signal for PCIe
Bit Rate	Min Height of the Eye at RX	Min Width of the Eye at RX
2.5 Gbps	175 mV	0.6 UI
5 Gbps	120 mV	0.6 UI

For more information about PCIe 2.0 base specification, see www.pcisig.com/members/downloads/specifications/pciexpress/PCI_Express_Base_r2_1_04Mar09.pdf.

To know if the system is meeting the requirements, the eye mask can be imported. Specifications of eye mask depend on the application the system is using. For example, PCIe 1.0, PCIe 2.0, XAUI, and SGMII. A typical eye mask for PCIe 2.0 is shown in the following figure.

Figure 2. Eye Mask for PCIe 2.0

For more information about IBIS-AMI model, see AC292- IBIS Models- Background and Usage Application Note.