5222-DS02-R datasheet(31/76 Pages) BOARDCOM

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Preliminary Data Sheet

BCM5222

7/20/04

Broadcom Corporation

Document 5222-DS02-405-R

MII Control Register

Page 19

POWER DOWN

The power modes of the BCM5222 are not accessible by this MII register bit. Use Shadow register control instead.

ISOLATE

The PHY can be isolated from its Media Independent Interface by writing a 1 to bit 10 of the Control register. All MII outputs

are tri-stated and all MII inputs are ignored. Because the MII 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.

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. 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. Because 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 8 of the Auxiliary Multiple PHY register

(1Eh).

Duplex Mode

This bit is logically or'd with the hardware pin, FDX, whenever Auto-negotiation is disabled.

COLLISION TEST

Test the COL pin by activating the collision test mode. While in this mode, asserting TXEN causes the COL output to go high

within 512 bit times. Deasserting TXEN causes the COL output to go low within 4 bit times. Writing a 1 to bit 7 of the Control

register enables the collision test mode. Writing a 0 to this bit or resetting the chip disables the collision test mode. When

this bit is read, it returns a 1 when the collision test mode has been enabled; otherwise it returns a 0. This bit should only be

set while in loopback test mode.

RESERVED BITS

All reserved MII register bits must be written as 0 at all times. Ignore the BCM5222 output when these bits are read.

5222-DS02-R 数据表(PDF) 31 Page - Broadcom Corporation.