ICS1893AFILF datasheet(61/137 Pages) RENESAS

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Chapter 8

Management Register Set

ICS1893AF, Rev. D 10/26/04

October, 2004

ICS1893AF Data Sheet - Release

8.2.5

Low Power Mode (bit 0.11)

This bit provides one way to control the ICS1893AF low-power mode function. When bit 0.11 is logic:

• Zero, there is no impact to ICS1893AF operations.

• One, the ICS1893AF enters the low-power mode. In this case, the ICS1893AF disables all internal

functions and drives all MAC/repeater output pins low except for those that support the MII Serial

Management Port. In addition, the ICS1893AF internally activates the TPTRI function to tri-state the

signals on the Twisted-Pair Transmit pins (TP_TXP and TP_TXN) and achieve additional power savings.

Note:

There are two ways the ICS1893AF can enter low-power mode. When entering low-power mode:

• By setting bit 0.11 to logic one, the ICS1893AF maintains the value of all Management Register

bits except the latching high (LH) and latching low (LL) status bits, which are re-initialized to their

default values instead. (For more information on latching high and latching low bits, see Section

8.1.4.1, “Latching High Bits” and Section 8.1.4.2, “Latching Low Bits”.)

• During a reset, the ICS1893AF sets all management register bits to their default values.

8.2.6

Isolate (bit 0.10)

This bit controls the ICS1893AF Isolate function. When bit 0.10 is logic:

• Zero, there is no impact to ICS1893AF operations.

• One, the ICS1893AF electrically isolates its data paths from the MAC/Repeater Interface. The

ICS1893AF places all MAC/repeater output signals (TXCLK, RXCLK, RXDV, RXER, RXD[3:0], COL,

and CRS) in a high-impedance state and it isolates all MAC/repeater input signals (TXD[3:0], TXEN, and

TXER). In this mode, the Serial Management Interface continues to operate normally (that is, bit 0.10

does not affect the Management Interface).

The default value for bit 0.10 depends upon the PHY address of Table 8-16. If the PHY address:

• Is equal to 00000b, then the default value of bit 0.10 is logic one, and the ICS1893AF isolates itself from

the MAC/Repeater Interface.

• Is not equal to 00000b, then the default value of bit 0.10 is logic zero, and the ICS1893AF does not

isolate its MAC/Repeater Interface.

8.2.7

Restart Auto-Negotiation (bit 0.9)

This bit allows an STA to restart the auto-negotiation process in Software mode (that is, the HW/SW pin is

logic one). When bit 0.12 is logic:

• Zero, the Auto-Negotiation sublayer is disabled, and the ICS1893AF isolates any attempt by the STA to

set bit 0.9 to logic one.

• One (as set by an STA), the ICS1893AF restarts the auto-negotiation process. Once the auto-negotiation

process begins, the ICS1893AF automatically sets this bit to logic zero, thereby providing the

self-clearing feature.

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