AC104Z datasheet(21/66 Pages) BOARDCOM

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Data Sheet

AC104Z

9/9/02

Br oad c om

Document

AC104Z-DS03-405-R

Initialization and Setup

Page 11

DIAGNOSTICS

Loopback Operation

Local Loopback is provided for testing and can be enabled by writing to Register 0.14 (LPBK).

The Local Loopback routes transmitted data through the transmit path back to the receiving path’s clock and data recovery

module. The loopback data are presented to the PCS in 5-bit symbol format. This loopback checks the operation of the 5-

bit symbol decoder and the phase locked loop circuitry. In Local Loopback, the SD output is forced to logic 1 and TXOP/N

outputs are tri-stated.

Cable Length Indicator

The Phy can detect the approximate length of the cable to which it’s attached and display the result in Register 20.[7:4]. A

reading of [0000] translates to < 10 meters of cable used, [0001] translates to ~ 10 meters of cable, and [1111] translates to

150 metes of cable. The cable length value can be used by the network manager to determine the proper connectivity of the

cable and to manage the cable plant distribution

RESET AND POWER

The Phy can be reset in three ways:

•

During initial power on.

•

Hardware Reset: A logic low signal of 150

µs pulse width is applied to RST* pin.

•

Software Reset: Write a one to SMI Reg. 0.15.

The device’s built-in power management features significantly reduce power consumption. Separate power supply lines

power the 10Base-T circuitry and the 100Base-TX circuitry. The two circuits, therefore, can be turned-on and turned-off

independently. When the Phy is set to operate in 100Base-TX mode, the 10Base-T circuitry is powered down, and vice

versa.

The following power management features are supported:

•

Power down mode: This can be achieved by writing to Register 0.11 or pulling PWRDN pin high. During power down

mode, the device is still able to interface through the MDC/MDIO management interface.

•

Energy-detect/power-saving mode: Energy-detect mode turns off the power to select internal circuitry when there is no

live network connected. The Energy Detect (ED) circuit is always turned on to monitor for a signal energy present on the

media. The SMI circuitry is also powered on and ready to respond to any management transaction. The transmit circuit

still sends out link pulses with minimum power consumption. If a valid signal is received from the media, the device

powers up and resumes normal transmit/receive operation. (Patent Pending)

•

Reduced Transmit Drive Strength mode: Additional power saving can be gained at the Phy level by designing with

1.25:1 turns ration magnetic and asserting the TP125 pin at reset.

CLOCK

The clock input must be a TTL clock oscillator measured at 125 MHz—100PPM for SMII or 50 MHz—100PPM for RMII.

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