Preliminary Data Sheet

12/11/01

B roa dcom Co rpo rat ion

Section 1: Functional Description

Document

AC104X-DS00-405-R

The AC104X supports the MDI/MDIX automatic configuration function. The automatic MDI/MDIX is intended to eliminate the

need for crossover cables between similar devices. The assignment of pin-outs for the Auto-MDI/MDIX is shown below:

Local Loopback is provided for testing purposes. It can be enabled by writing to Reg. 0.14.

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 bits symbol format. This loopback is used to check the operation

of the 5-bit symbol decoder and the phase locked loop circuitry. In Local Loopback, the SD output is forced to logic one and

TXOP/N outputs are tri-stated.

In 100BASE-T mode, the PHY can detect the approximate length of the cable it's attached and display the result in Reg.

20.[7:4]. A reading of [0000] translates to < 10m cable used, [0001] translates to ~ 10 meter of cable, and [1111] translates

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

cable and to manage the cable plant distribution

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 power consumption of the device is significantly reduced due to its built-in power management features. Separate power

supply lines are used to power the 10BASE-T circuitry and the 100BASE-TX circuitry. Therefore, the two circuits 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 be able to interface through the MDC/MDIO management interface.

Table 1:

Auto-MDI/MDIX Pinout Assignments

Contact

PHY

MDI

MDIX

1

TXOP

TXOP

RXIP

2

TXON

TXON

RXIN

3

RXIP

RXIP

TXOP

4N/C

N/C

N/C

5N/C

N/C

N/C

6

RXIN

RXIN

TXON

7N/C

N/C

N/C

8N/C

N/C

N/C