PCI Express
16.5
Receiver Compliance Eye Diagrams
The RX eye diagram in
Figure 56
is specified using the passive compliance/test measurement load (see
Figure 57)
in place of any real PCI Express RX component.
load (see
Figure 57)
is larger than the minimum Receiver eye diagram measured over a range of systems
at the input Receiver of any real PCI Express component. The degraded eye diagram at the input Receiver
is due to traces internal to the package as well as silicon parasitic characteristics which cause the real PCI
Express component to vary in impedance from the compliance/test measurement load. The input Receiver
eye diagram is implementation specific and is not specified. RX component designer should provide
additional margin to adequately compensate for the degraded minimum Receiver eye diagram (shown in
Figure 56)
expected at the input Receiver based on some adequate combination of system simulations and
the Return Loss measured looking into the RX package and silicon. The RX eye diagram must be aligned
The eye diagram must be valid for any 250 consecutive UIs.
A recovered TX UI is calculated over 3500 consecutive unit intervals of sample data. The eye diagram is
created using all edges of the 250 consecutive UI in the center of the 3500 UI used for calculating the TX
UI.
NOTE
The reference impedance for return loss measurements is 50. to ground for
both the D+ and D- line (that is, as measured by a Vector Network Analyzer
with 50. probes—see
Figure 57).
Note that the series capacitors, CTX, are
optional for the return loss measurement.
Figure 56. Minimum Receiver Eye Timing and Voltage Compliance Specification
MPC8572E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 4
Freescale Semiconductor
89
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
