MPC8568E datasheet(17/139 Pages) FREESCALE

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MPC8568E/MPC8567E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 1

Freescale Semiconductor

Input Clocks

4.4

eTSEC Gigabit Reference Clock Timing

Table 9 provides the eTSEC gigabit reference clocks (EC_GTX_CLK125) AC timing specifications for

the MPC8568E.

4.5

FIFO Clock Speed Restrictions

Note the following FIFO maximum speed restrictions based on the platform speed.

For FIFO GMII mode:

FIFO TX/RX clock frequency <= platform clock frequency / 4.2

For example, if the platform frequency is 533 MHz, the FIFO TX/RX clock frequency should be no higher

than 127 MHz.

For FIFO encoded mode:

FIFO TX/RX clock frequency <= platform clock frequency / 3.2

For example, if the platform frequency is 533 MHz, the FIFO TX/RX clock frequency should be no higher

than 167 MHz

4.6

Other Input Clocks

For information on the input clocks of other functional blocks of the platform such as SerDes, and eTSEC,

see the specific section of this document.

Table 9. EC_GTX_CLK125 AC Timing Specifications

Parameter/Condition

Symbol

Min

Typical

Max

Unit

Notes

EC_GTX_CLK125 frequency

fG125

—125

—

MHz

—

EC_GTX_CLK125 cycle time

tG125

—8

—

EC_GTX_CLK125 rise and fall time

L/TVDD = 2.5 V

L/TVDD = 3.3 V

tG125R, tG125F

—

0.75

1.0

—

EC_GTX_CLK125 duty cycle

GMII, TBI

1000Base-T for RGMII, RTBI

tG125H/tG125

—

%1, 2

Notes:

1. Timing is guaranteed by design and characterization.

2. EC_GTX_CLK125 is used to generate the GTX clock for the eTSEC transmitter with 2% degradation.

EC_GTX_CLK125 duty cycle can be loosened from 47/53% as long as the PHY device can tolerate the duty cycle

generated by the eTSEC GTX_CLK. See Section 8.2.6, “RGMII and RTBI AC Timing Specifications,” for duty cycle

for 10Base-T and 100Base-T reference clock.

3. Rise and fall times for EC_GTX_CLK125 are measured from 0.5 and 2.0 V for L/TVDD = 2.5 V, and from 0.6 and 2.7

V for L/TVDD = 3.3 V.

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