SPEAR1340 datasheet(164/200 Pages) STMICROELECTRONICS

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Timing characteristics

SPEAr1340

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Doc ID 023063 Rev 4

5.7

GMAC timing characteristics

This section describes the AC timing characteristics for the Giga/Fast Ethernet port. The

GMAC is designed to support 10, 100 and 1000 Mbps Ethernet/IEEE 802.3 networks. It

supports GMII, RMII and MII interfaces.

Note:

For the pin list of the supported interfaces, see Table 5: MAC Ethernet port multiplexing

scheme and Table 15: Connectivity - MAC PHY interface signals description.

5.7.1

GMII transmit timing characteristics

The timing characterization is performed assuming an output load capacitance of 10 pF on

the output pads and using PLL2 as internal clock source or MAC_GTXCLK125 as external

clock source for GMII TX interface timings extraction.

These timings are valid for 10, 100 and 1000 Mbps operation.

Figure 25.

GMII TX timing waveform

MAC_GTXCLK

(output)

MAC_TXD0 - MAC_TXD7,

MAC_TXEN, MAC_TXER

TCLKhigh

TCLKlow

Table 73.

GMII TX timing characteristics

Parameter

Description

Conditions(1)

Min

Max

Unit

TCLK

MAC_GTXCLK clock period

TCLKhigh

MAC_GTXCLK pulse high

Clock source=

MAC_GTXCLK125@125 MHz

(50% ideal duty cycle)

1.5

TCLKlow

MAC_GTXCLK pulse low

1.0

TCLKhigh

MAC_GTXCLK pulse high

Clock source=

MAC_GTXCLK125@250 MHz

internally divided by 2

2.1

TCLKlow

MAC_GTXCLK pulse low

1.4

TCLKhigh

MAC_GTXCLK pulse high

Clock source= PLL2

2.2

TCLKlow

MAC_GTXCLK pulse low

1.2

MAC_GTXCLK to GMII output

data

0.4

5.6

Characterizations based on external clock sources are performed assuming an ideal 50% duty cycle clock.

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