LAN8740A Datasheet, PDF(25/136 Page) Microchip Technology – Small Footprint MII/RMII 10/100 Energy Efficient Ethernet Transceiver with HP Auto-MDIX and flexPWR® Technology

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

LAN8740A Datasheet, PDF (25/136 Pages) Microchip Technology – Small Footprint MII/RMII 10/100 Energy Efficient Ethernet Transceiver with HP Auto-MDIX and flexPWR® Technology

◁

LAN8740A/LAN8740Ai

3.3 HP Auto-MDIX Support

HP Auto-MDIX facilitates the use of CAT-3 (10BASE-T) or CAT-5 (100BASE-TX) media UTP interconnect cable without

consideration of interface wiring scheme. If a user plugs in either a direct connect LAN cable, or a cross-over patch

cable, as shown in Figure 3-4, the deviceâs Auto-MDIX transceiver is capable of configuring the TXP/TXN and RXP/RXN

pins for correct transceiver operation.

The internal logic of the device detects the TX and RX pins of the connecting device. Since the RX and TX line pairs

are interchangeable, special PCB design considerations are needed to accommodate the symmetrical magnetics and

termination of an Auto-MDIX design.

The Auto-MDIX function can be disabled via the AMDIXCTRL bit in the Special Control/Status Indications Register.

Note:

When operating in 10BASE-T or 100BASE-TX manual modes, the Auto-MDIX crossover time can be

extended via the Extend Manual 10/100 Auto-MDIX Crossover Time bit of the EDPD NLP/Crossover

Time/EEE Configuration Register. Refer to Section 4.2.12, "EDPD NLP/Crossover Time/EEE Configura-

tion Register" for additional information.

FIGURE 3-4:

DIRECT CABLE CONNECTION VS. CROSS-OVER CABLE CONNECTION

RJ-45 8-pin straight-through

for 10BASE-T/100BASE-TX

signaling

TXP 1

TXN 2

RXP 3

Not Used 4

Not Used 5

RXN 6

Not Used 7

Not Used 8

1 TXP

2 TXN

3 RXP

4 Not Used

5 Not Used

6 RXN

7 Not Used

8 Not Used

Direct Connect Cable

RJ-45 8-pin cross-over for

10BASE-T/100BASE-TX