LXT975B datasheet(13/74 Pages) INTEL

13 / 74 page

Fast Ethernet 10/100 Quad Transceivers — LXT974/LXT975

Datasheet

Table 4.

LXT975 Signal Detect/TP Select Signal Descriptions

Pin#2

Symbol

Type1

Signal Description

149

130

SD1/TP1

SD3/TP3

Signal Detect - Ports 1 & 3. When SD/TPn pins are tied High or to a 5V PECL input, bit

19.2 = 1 and the operating mode of each respective port is forced to FX mode. In this

mode, full-duplex is set via pin 117 (FDE_FX). When not using fiber mode, SD/TPn pins

should be tied to GNDT.

TP Select - Ports 1 & 3. When SD/TPn pins are tied Low, bit 19.2 = 0. The operating mode

of each port can be set to 10BASE-T, 100BASE-TX, or 100BASE-FX via the hardware

control interface pins as shown in Table 8 on page 16.

Note: Hardware control interface pins (CFG_0, CFG_1, CFG_2, FDE, BYPSCR, and

AUTOENA) are global and set all ports simultaneously.

In TP mode, network pins operate as described in Table 5.

In FX mode, network pins are re-mapped and operate as described in Table 6.

1. Type Column Coding: I = Input, O = Output.

2. When not using fiber mode, SD/TPn pins should be tied to GNDT.

Table 5.

LXT975 Twisted-Pair Interface Signal Descriptions

Pin#

Symbol

Type1

Signal Description

155, 152

145, 148

136, 133

126, 129

TPOP0, TPON0

TPOP1, TPON1

TPOP2, TPON2

TPOP3, TPON3

Twisted-Pair Outputs, Positive & Negative - Ports 0-3.

During 100BASE-TX or 10BASE-T operation, TPO pins drive 802.3 compliant

pulses onto the line.

158, 157

142, 143

139, 138

123, 124

TPIP0, TPIN0

TPIP1, TPIN1

TPIP2, TPIN2

TPIP3, TPIN3

Twisted-Pair Inputs, Positive & Negative - Ports 0-3.

During 100BASE-TX or 10BASE-T operation, TPI pins receive differential

100BASE-TX or 10BASE-T signals from the line.

1. Type Column Coding: I = Input, O = Output.

Table 6.

LXT975 Fiber Interface Signal Descriptions

Pin#

Symbol

Type1

Signal Description

145, 148

126, 129

FIBIN1, FIBIP1

FIBIN3, FIBIP3

Fiber Network Interface - Ports 1 and 3

During 100BASE-FX operation, FIBI pins receive differential PECL inputs

from fiber transceivers.

142, 143

123, 124

FIBOP1, FIBON1

FIBOP3, FIBON3

Fiber Network Interface - Ports 1 and 3

During 100BASE-FX operation, FIBO pins produce differential PECL

outputs for fiber transceivers.

1. Type Column Coding: I = Input, O = Output.

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