MPC8548ECPXATHC datasheet(28/151 Pages) FREESCALE

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MPC8548E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 9

Freescale Semiconductor

Enhanced Three-Speed Ethernet (eTSEC)

8.2

FIFO, GMII, MII, TBI, RGMII, RMII, and RTBI AC Timing

Specifications

The AC timing specifications for FIFO, GMII, MII, TBI, RGMII, RMII, and RTBI are presented in this

section.

8.2.1

FIFO AC Specifications

The basis for the AC specifications for the eTSEC’s FIFO modes is the double data rate RGMII and RTBI

specifications, since they have similar performances and are described in a source-synchronous fashion

like FIFO modes. However, the FIFO interface provides deliberate skew between the transmitted data and

source clock in GMII fashion.

When the eTSEC is configured for FIFO modes, all clocks are supplied from external sources to the

relevant eTSEC interface. That is, the transmit clock must be applied to the eTSECn’s TSECn_TX_CLK,

while the receive clock must be applied to pin TSECn_RX_CLK. The eTSEC internally uses the transmit

clock to synchronously generate transmit data and outputs an echoed copy of the transmit clock back out

onto the TSECn_GTX_CLK pin (while transmit data appears on TSECn_TXD[7:0], for example). It is

intended that external receivers capture eTSEC transmit data using the clock on TSECn_GTX_CLK as a

source- synchronous timing reference. Typically, the clock edge that launched the data can be used, since

the clock is delayed by the eTSEC to allow acceptable set-up margin at the receiver. Note that there is

relationship between the maximum FIFO speed and the platform speed. For more information see

Section 4.5, “Platform to FIFO Restrictions.”

Table 23. GMII, MII, RMII, TBI, RGMII, RTBI, and FIFO DC Electrical Characteristics

Parameters

Symbol

Min

Max

Unit

Notes

Supply voltage 2.5 V

LVDD/TVDD

2.37

2.63

1, 2

Output high voltage (LVDD/TVDD = Min,

IOH = –1.0 mA)

VOH

2.00

LVDD/TVDD + 0.3

—

Output low voltage (LVDD/TVDD = Min,

IOL = 1.0 mA)

VOL

GND

–0.3

0.40

—

Input high voltage

VIH

1.70

LVDD/TVDD + 0.3

—

Input low voltage

VIL

–0.3

0.90

—

Input high current (VIN = LVDD, VIN = TVDD)IIH

—10

A

1, 2, 3

Input low current (VIN = GND)

IIL

–15

—

A3

Notes:

1. LVDD supports eTSECs 1 and 2.

2. TVDD supports eTSECs 3 and 4.

3. Note that the symbol VIN, in this case, represents the LVIN and TVIN symbols referenced in Table 1 and Table 2.

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