MPC8548E datasheet(70/143 Pages) FREESCALE

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MPC8548E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 8

Freescale Semiconductor

PCI Express

17.3

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.

17.4

Physical Layer Specifications

The 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 refer to PCI Express Base

Specification. Rev. 1.0a.

17.4.1

Differential Transmitter (TX) Output

Table 56 defines the specifications for the differential output at all transmitters (TXs). The parameters are

specified at the component pins.

Table 56. Differential Transmitter (TX) Output Specifications

Symbol

Parameter

Min

Nom

Max

Unit

Comments

Unit interval

399.88

400

400.12

Each UI is 400 ps ± 300 ppm. UI does not account

for spread spectrum clock dictated variations.

See Note 1.

VTX-DIFFp-p

Differential

peak-to-peak

output voltage

0.8

—

1.2

VTX-DIFFp-p = 2 × |VTX-D+ – VTX-D–|. See Note 2.

VTX-DE-RATIO

De- emphasized

differential

output voltage

(ratio)

–3.0

–3.5

–4.0

Ratio of the VTX-DIFFp-p of the second and

following bits after a transition divided by the

VTX-DIFFp-p of the first bit after a transition.

See Note 2.

TTX-EYE

Minimum TX eye

width

0.70

—

The maximum transmitter jitter can be derived as

TTX-MAX-JITTER = 1 – TTX-EYE = 0.3 UI.

See Notes 2 and 3.

TTX-EYE-MEDIAN-to-

MAX-JITTER

Maximum time

between the

jitter median and

maximum

deviation from

the median.

—

0.15

Jitter is defined as the measurement variation of

the crossing points (VTX-DIFFp-p = 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.

See Notes 2 and 3.

TTX-RISE, TTX-FALL

D+/D– TX output

rise/fall time

0.125

—

See Notes 2 and 5.

VTX-CM-ACp

RMS AC peak

common mode

output voltage

——

VTX-CM-ACp = RMS(|VTXD+ + VTXD–|/2 –

VTX-CM-DC)

VTX-CM-DC = DC(avg) of |VTX-D+ + VTX-D–|/2.

See Note 2.

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