5228-DS07-R datasheet(52/100 Pages) BOARDCOM

52 / 100 page

BCM5228

Data Sheet

7/12/04

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

Page 40

MII Management Interface: Register Programming

Document

5228-DS09-405-R

effect when auto-negotiation has been disabled by hardware control. When read, this bit returns the value most recently

written to this location, or 1 if it has not been written since the last chip reset.

Power Down. The BCM5228 does not implement power-down mode. However, the device does support auto power-down

mode (see “Auto Power-Down Mode” on page 26).

Isolate. Each individual PHY can be isolated from its Media Independent Interface by writing a 1 to bit 10 of the Control

register. All RMII outputs is tri-stated and all RMII/SMII/S3MII inputs are ignored. Because the MII/SMII/S3MII management

interface is still active, the isolate mode can be cleared by writing a 0 to bit 10 of the Control register, or by resetting the chip.

When this bit is read, it returns a 1 when the chip is in isolate mode, otherwise, it returns a 0. See also “Isolate

Mode” on page 26.

Restart Auto-Negotiation. Bit 9 of the Control register is a self-clearing bit that allows the auto-negotiation process

to be restarted, regardless of the current status of the auto-negotiation state machine. In order for this bit to have

an effect, auto-negotiation must be enabled. Writing a 1 to this bit restarts the auto-negotiation, while writing a 0 to

this bit has no effect. Since the bit is self-clearing after only a few cycles, it always returns a 0 when read. The

operation of this bit is identical to bit 9 of the Auxiliary Multiple PHY register.

Duplex Mode. By default, the BCM5228 powers up in half-duplex mode. The chip can be forced into full-duplex mode by

writing a 1 to bit 8 of the Control register while auto-negotiation is disabled. Half-duplex mode can be resumed by writing a

0 to bit 8 of the Control register, or by resetting the chip.

5228-DS07-R 数据表(PDF) 52 Page - Broadcom Corporation.