LAN9354 datasheet(86/487 Pages) MICROCHIP

86 / 487 page

LAN9354

DS00001926B-page 86

 2015 Microchip Technology Inc.

9.2.6.5

Half Vs. Full-Duplex

Half-duplex operation relies on the CSMA/CD (Carrier Sense Multiple Access / Collision Detect) protocol to handle net-

work traffic and collisions. In this mode, the carrier sense signal, CRS, responds to both transmit and receive activity. If

data is received while the transceiver is transmitting, a collision results.

In full-duplex mode, the transceiver is able to transmit and receive data simultaneously. In this mode, CRS responds

only to receive activity. The CSMA/CD protocol does not apply and collision detection is disabled.

9.2.7

HP AUTO-MDIX

HP Auto-MDIX facilitates the use of CAT-3 (10 BASE-T) or CAT-5 (100 BASE-T) 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 9-4, the transceiver is capable of configuring the TXPx/TXNx and RXPx/RXNx twisted pair 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 is enabled using the auto_mdix_strap_1 and auto_mdix_strap_2 configuration straps. Manual

selection of the cross-over can be set using the manual_mdix_strap_1 and manual_mdix_strap_2 configuration straps.

Software based control of the Auto-MDIX function may be performed using the Auto-MDIX Control (AMDIXCTRL) bit of

the PHY x Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x). When AMDIXCTRL

is set to 1, the Auto-MDIX capability is determined by the Auto-MDIX Enable (AMDIXEN) and Auto-MDIX State (AMDIX-

STATE) bits of the PHY x Special Control/Status Indication Register (PHY_SPECIAL_CONTROL_STAT_IND_x).

Note:

Auto-MDIX is not used for 100BASE-FX mode.

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 PHY x EDPD NLP / Cross-

over Time / EEE Configuration Register (PHY_EDPD_CFG_x). Refer to Section 9.2.20.12, on page 120

for additional information.

When Energy Detect Power-Down is enabled, the Auto-MDIX crossover time can be extended via the

EDPD Extend Crossover bit of the PHY x EDPD NLP / Crossover Time / EEE Configuration Register

(PHY_EDPD_CFG_x). Refer to Section 9.2.20.12, on page 120 for additional information

FIGURE 9-4:

DIRECT CABLE CONNECTION VS. CROSS-OVER CABLE CONNECTION

TXPx

TXNx

RXPx

Not Used

RXNx

Not Used

TXPx

TXNx

RXPx

Not Used

RXNx

Not Used

Direct Connect Cable

RJ-45 8-pin straight-through

for 10BASE-T/100BASE-TX

signaling

TXPx

TXNx

RXPx

Not Used

RXNx

Not Used

TXPx

TXNx

RXPx

Not Used

RXNx

Not Used

Cross-Over Cable

RJ-45 8-pin cross-over for

10BASE-T/100BASE-TX

signaling

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