5220-DS02-R datasheet(56/90 Pages) BOARDCOM

56 / 90 page

BCM5220

Preliminary Data Sheet

04/20/04

Broa d c om Co rp o r a t i o n

Page 44

Auxiliary Control/Status Register

Document

5220-DS04-405-R

over longer cable lengths. Decreasing the squelch levels can be useful in situations where there is a high level of noise

present on the cables. Reading these 2 bits returns the value of the squelch levels.

Edge Rate

Control bits used to program the transmit DAC output edge rate in 100BASE-TX mode. A larger value on these bits produces

slower transitions on the transmit waveform.

Auto-Negotiation Indication

This read-only bit indicates whether auto-negotiation has been enabled or disabled on the BCM5220. A combination of a 1

in bit 12 of the Control register and a logic 1 on the ANEN input pin is required to enable auto-negotiation. When auto-

negotiation is disabled, bit 3 of the Auxiliary Control register (18h) returns a 0. At all other times, it returns a 1.

Force100/10 Indication

This read-only bit returns a value of 0 when one of following cases is true:

•

The ANEN pin is low AND the F100 pin is low.

•

The ANEN pin is high AND bit 12 of the Control register has been written 0 and bit 13 of the Control register has been

written 0.

When bit 2 of the Auxiliary Control register (18h) is 0, the speed of the chip is 10BASE-T. In all other cases, either the speed

is not forced (auto-negotiation is enabled), or the speed is forced to 100BASE-X.

Speed Indication

This read-only bit shows the true current operation speed of the BCM5220. A 1 indicates 100BASE-X operation, and a 0

indicates 10BASE-T. While the auto-negotiation exchange is performed, the BCM5201 is always operating at 10BASE-T

speed.

Full-Duplex Indication

This read-only bit returns a 1 when the BCM5220 is in full-duplex mode. In all other modes, it returns a 0.

5220-DS02-R 数据表(PDF) 56 Page - Broadcom Corporation.