ICS1893 datasheet(77/153 Pages) RENESAS

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Chapter 8

Management Register Set

ICS1893 Rev C 6/6/00

June, 2000

ICS1893 - Release

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 ICS1893 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

reserved bits to invoke auxiliary functions. To ensure proper operation of the ICS1893, 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 ICS1893 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 ICS1893 Auto-Negotiation sublayer is enabled, the ICS1893 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 ICS1893 exchanges with its remote link partner. The ICS1893 sets this bit to logic one

whenever it detects a problem with the link, locally. The data in this register is sent to the remote link partner

to inform it of the potential problem. If the ICS1893 does not detect a link fault, it clears bit 4.13 to logic zero.

Whenever the ICS1893:

• Does not detect a link fault, the ICS1893 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

IEEE Reserved Bits (bits 4.12:10)

The IEEE reserves these bits for future use. When an STA:

• Reads a reserved bit, the ICS1893 returns a logic zero.

• Writes to a reserved bit, it must use the default value specified in this data sheet.

The ICS1893 uses some reserved bits to invoke auxiliary functions. To ensure proper operation of the

ICS1893, an STA must maintain the default value of these bits. Therefore, ICS recommends that during

any STA write operation, an STA write the default value to all reserved bits, even those bits that are Read

Only.

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