ICS1892Y datasheet(76/148 Pages) ICST

76 / 148 page

ICS1892, Rev. D, 2/26/01

February 26, 2001

Chapter 8

Management Register Set

ICS1892 Data Sheet

8.6.2

IEEE Reserved Bit (bit 4.14)

The ISO/IEC specification reserves this bit for future use. However, the ISO/IEC Standard also defines bit

4.14 as the Acknowledge bit.

When this reserved bit is read by an STA, the ICS1892 returns a logic zero. However, whenever an STA

writes to this reserved bit, it must use the default value specified in this data sheet. ICS uses some of these

reserved bits to invoke auxiliary functions. To ensure proper operation of the ICS1892, an STA must

maintain the default value of these bits. Therefore, ICS recommends that an STA always write the default

value of any reserved bits during all management register write operations.

Reserved bit 4.14 is a Command Override Write (CW) bit. Whenever bit 16.15 (the Command Register

Override bit) is logic:

• Zero, the ICS1892 isolates all STA writes to bit 4.14.

• One, an STA can modify the value of bit 4.14.

8.6.3

Remote Fault (bit 4.13)

When the ICS1892 Auto-Negotiation sublayer is enabled, the ICS1892 transmits the Remote Fault bit 4.13

to its remote link partner during the auto-negotiation process. The Remote Fault bit is part of the Link Code

Word that the ICS1892 exchanges with its remote link partner. The ICS1892 sets this bit to logic one

whenever it detects a problem with the link, locally. This data is sent to the remote link partner to inform it

of the potential problem. If the ICS1892 does not detect a link fault, it clears bit 4.13 to logic zero.

Whenever the ICS1892:

• Does not detect a link fault, the ICS1892 clears bit 4.13 to logic zero.

• Detects a problem with the link, during the auto-negotiation process, this bit is set. As a result, the data

on this bit is sent to the remote link partner to inform it of the potential problem.

8.6.4

Technology Ability Field (bits 4.12:5)

When its Auto-Negotiation sublayer is enabled, the ICS1892 transmits its link capabilities to its remote link

partner during the auto-negotiation process. The Technology Ability Field (TAF) bits 4.12:5 determine the

specific abilities that the ICS1892 advertises. The ISO/IEC specification defines the TAF technologies in

Annex 28B.

The ISO/IEC specification reserves bits 4.12:10 for future use. When each of these reserved bits is:

• Read by an STA, the ICS1892 returns a logic zero

• Written to by an STA, the STA must use the default value specified in this data sheet.

ICS uses some of these reserved bits to invoke auxiliary functions. To ensure proper operation of the

ICS1892, an STA must maintain the default value of these bits. Therefore, ICS recommends that an STA

always write the default value of any reserved bits during all management register write operations.

Reserved bits 4.12:10 are Command Override Write (CW) bits. Whenever bit 16.15 (the Command

• Zero, the ICS1892 isolates all STA writes to CW bits, including bits 4.12:10.

• One, an STA can modify the value of bits 4.12:10

Each of the bits 4.9:5 in the TAF represent a specific technology capability. When one of these bits is logic:

• Zero, it indicates to the remote link partner that the local device cannot support the technology

represented by the bit.

• One, it indicates to the remote link partner that the local device can support the technology.

With the exception of bit 4.9, the default settings of the TAF bits depend on the ICS1892 operating mode.

Bit 4.9 is always logic zero, indicating that the ICS1892 cannot support 100Base-T4 operations.

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