MPC8308 datasheet(35/88 Pages) FREESCALE

35 / 88 page

MPC8308 PowerQUICC II Pro Processor Hardware Specification, Rev. 0

Freescale Semiconductor

PCI Express

11.3

Clocking Dependencies

The ports on the two ends of a link must transmit data at a rate that is within 600 parts per million (ppm)

of each other at all times. This is specified to allow bit rate clock sources with a ±300 ppm tolerance.

11.4

Physical Layer Specifications

Following is a summary of the specifications for the physical layer of PCI Express on this device. For

further details as well as the specifications of the transport and data link layer please use the PCI Express

Base Specification, Rev. 1.0a.

11.4.1

Differential Transmitter (TX) Output

Table 34 defines the specifications for the differential output at all transmitters (TXs). The parameters are

specified at the component pins.

Table 34. Differential Transmitter (TX) Output Specifications

Parameter

Symbol

Comments

Min

Typical

Max

Units

Notes

Unit interval

Each UPETX is 400 ps ±

300 ppm. UPETX does not

account for Spread

Spectrum Clock dictated

variations.

399.88

400

400.12

Differential peak-to-peak

output voltage

VTX-DIFFp-p

VPEDPPTX = 2*|VTX-D+ -

VTX-D-|

0.8

—

1.2

De-Emphasized

differential output voltage

(ratio)

VTX-DE-RATIO

Ratio of the VPEDPPTX of

the second and following

bits after a transition

divided by the VPEDPPTX

of the first bit after a

transition.

–3.0

–3.5

–4.0

Minimum TX eye width

TTX-EYE

The maximum Transmitter

jitter can be derived as

TTX-MAX-JITTER = 1 -

UPEEWTX= 0.3 UI.

0.70

——UI

2, 3

Maximum time between

the jitter median and

maximum deviation from

the median

TTX-EYE-MEDIAN-t

MAX-JITTER

Jitter is defined as the

measurement variation of

the crossing points

(VPEDPPTX = 0 V) in

relation to a recovered TX

UI. A recovered TX UI is

calculated over 3500

consecutive unit intervals

of sample data. Jitter is

measured using all edges

of the 250 consecutive UI

in the center of the 3500

UI used for calculating the

TX UI.

—

0.15

2, 3

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