MPC8640DEC datasheet(73/140 Pages) FREESCALE

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MPC8640 and MPC8640D Integrated Host Processor Hardware Specifications, Rev. 1

Freescale Semiconductor

PCI Express

14.4.2

Transmitter Compliance Eye Diagrams

The TX eye diagram in Figure 50 is specified using the passive compliance/test measurement load (see

Figure 52) in place of any real PCI Express interconnect + RX component.

There are two eye diagrams that must be met for the transmitter. Both eye diagrams must be aligned in

time using the jitter median to locate the center of the eye diagram. The different eye diagrams will differ

in voltage depending whether it is a transition bit or a de-emphasized bit. The exact reduced voltage level

of the de-emphasized bit will always be relative to the transition bit.

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

It is recommended that the recovered TX UI is calculated using all edges in

the 3500 consecutive UI interval with a fit algorithm using a minimization

merit function (i.e., least squares and median deviation fits).

Tcrosslink

Crosslink

Random

Timeout

This random timeout helps resolve conflicts in

crosslink configuration by eventually resulting in only

one Downstream and one Upstream Port. See Note 7.

Notes:

1.) No test load is necessarily associated with this value.

2.) Specified at the measurement point into a timing and voltage compliance test load as shown in Figure 52 and measured over

any 250 consecutive TX UIs. (Also refer to the transmitter compliance eye diagram shown in Figure 50)

3.) A TTX-EYE = 0.70 UI provides for a total sum of deterministic and random jitter budget of TTX-JITTER-MAX = 0.30 UI for the

Transmitter collected over any 250 consecutive TX UIs. The TTX-EYE-MEDIAN-to-MAX-JITTER median is less than half of the total

TX jitter budget collected over any 250 consecutive TX UIs. It should be noted that the median is not the same as the mean.

The jitter median describes the point in time where the number of jitter points on either side is approximately equal as opposed

to the averaged time value.

4.) The Transmitter input impedance shall result in a differential return loss greater than or equal to 12 dB and a common mode

return loss greater than or equal to 6 dB over a frequency range of 50 MHz to 1.25 GHz. This input impedance requirement

applies to all valid input levels. The reference impedance for return loss measurements is 50 ohms to ground for both the D+

and D- line (that is, as measured by a Vector Network Analyzer with 50 ohm probes—see Figure 52). Note that the series

capacitors CTX is optional for the return loss measurement.

5.) Measured between 20-80% at transmitter package pins into a test load as shown in Figure 52 for both VTX-D+ and VTX-D-.

6.) See Section 4.3.1.8 of the PCI Express Base Specifications Rev 1.0a

7.) See Section 4.2.6.3 of the PCI Express Base Specifications Rev 1.0a

Table 48. Differential Transmitter (TX) Output Specifications (continued)

Symbol

Parameter

Min

Nom

Max

Units

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