LAN83C185 datasheet(46/61 Pages) SMSC

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High Performance Single Chip Low Power 10/100 Ethernet Physical Layer Transceiver (PHY)

Datasheet

Rev. 0.8 (11-16-04)

SMSC LAN83C185

DATASHEET

Figure 5.1 PHY Address Strapping on LEDS

The ACTIVITY LED output is driven active when CRS is active (high). When CRS becomes inactive,

the Activity LED output is extended by 128ms.

The LINKON LED output is driven active whenever the PHY detects a valid link. The use of the

10Mbps or 100Mbps link test status is determined by the condition of the internally determined speed

selection.

The SPEED100 LED output is driven active when the operating speed is 100Mbit/s or during Auto-

negotiation. This LED will go inactive when the operating speed is 10Mbit/s or during line isolation

(register 31 bit 5).

The Full-Duplex LED output is driven active low when the link is operating in Full-Duplex mode.

5.4.8

Loopback Operation

The 10/100 digital has two independent loop-back modes: Internal loopback and far loopback.

5.4.8.1

Internal Loopback

The internal loopback mode is enabled by setting bit register 0 bit 14 to logic one. In this mode, the

scrambled transmit data (output of the scrambler) is looped into the receive logic (input of the

descrambler). The COL signal will be inactive in this mode, unless collision test (bit 0.7) is active.

In this mode, during transmission (TX_EN is HIGH), nothing is transmitted to the line and the

transmitters are powered down.

5.4.9

Configuration Signals

The PHY has 11 configuration signals whose inputs should be driven continuously, either by external

logic or external pull-up/pull-down resistors.

5.4.9.1

Physical Address Bus - PHYAD[4:0]

The PHYAD[4:0] signals are driven high or low to give each PHY a unique address. This address is

latched into an internal register at end of hardware reset. In a multi-PHY application (such as a

repeater), the controller is able to manage each PHY via the unique address. Each PHY checks each

management data frame for a matching address in the relevant bits. When a match is recognized, the

PHY responds to that particular frame. The PHY address is also used to seed the scrambler. In a multi-

PHY application, this ensures that the scramblers are out of synchronization and disperses the

electromagnetic radiation across the frequency spectrum.

LED1-LED4

~270 ohms

Phy Address = 0

LED output = active high

~10K ohms

~270 ohms

LED1-LED4

VDD

Phy Address = 1

LED output = active low

LAN83C185 Datasheet(PDF) 46 Page - SMSC Corporation

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