MPC8540CPX667JC datasheet(64/104 Pages) FREESCALE

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MPC8540 Integrated Processor Hardware Specifications, Rev. 4

Freescale Semiconductor

RapidIO

enough that increasing the length of the sequence does not cause the resulting eye pattern to change from

one that complies with the RapidIO receive mask to one that does not comply with the mask. The data

carried by any given data signal in the interface may not be correlated with the data carried by any other

data signal in the interface. The zero-crossings of the clock associated with a data signal shall be used as

the timing reference for aligning the multiple recordings of the data signal when the recordings are

overlaid.

While the method used to make the recordings and overlay them to form the eye pattern is not specified,

the method used shall be demonstrably equivalent to the following method. The signal under test is

repeatedly recorded with a digital oscilloscope in infinite persistence mode. Each recording is triggered by

a zero-crossing of the clock associated with the data signal under test. Roughly half of the recordings are

triggered by positive-going clock zero-crossings and roughly half are triggered by negative-going clock

zero-crossings. Each recording is at least 1.9 UI in length (to ensure that at least one complete eye is

formed) and begins 0.5 UI before the trigger point (0.5 UI before the associated clock zero-crossing).

Depending on the length of the individual recordings used to generate the eye pattern, one or more

complete eyes will be formed. Regardless of the number of eyes, the eye whose center is immediately to

the right of the trigger point is the eye used for compliance testing.

An example of an eye pattern generated using the above method with recordings 3 UI in length is shown

in Figure 40. In this example, there is no skew between the signal under test and the associated clock used

to trigger the recordings. If skew was present, the eye pattern would be shifted to the left or right relative

to the oscilloscope trigger point.

Figure 40. Example Receiver Input Eye Pattern

–

0.5 UI

1.0 UI

Oscilloscope

(Recording)

Trigger Point

Eye Pattern

Eye Used for

Compliance

Testing

MPC8540CPX667JC 数据表(PDF) 64 Page - Freescale Semiconductor, Inc