ICS1893BF Data Sheet - Release
Chapter 7 Management Register Set
7.6.2 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 ICS1893BF 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 ICS1893BF, 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 ICS1893BF isolates all STA writes to bit 4.14.
• One, an STA can modify the value of bit 4.14.
7.6.3 Remote Fault (bit 4.13)
When the ICS1893BF Auto-Negotiation sublayer is enabled, the ICS1893BF 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 ICS1893BF exchanges with its remote link partner. The ICS1893BF 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 ICS1893BF does not detect a link fault, it clears bit 4.13
to logic zero.
Whenever the ICS1893BF:
• Does not detect a link fault, the ICS1893BF 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.
7.6.4 IEEE Reserved Bits (bits 4.12:10)
The IEEE reserves these bits for future use. When an STA:
• Reads a reserved bit, the ICS1893BF returns a logic zero.
• Writes to a reserved bit, it must use the default value specified in this data sheet.
The ICS1893BF uses some reserved bits to invoke auxiliary functions. To ensure proper operation of the
ICS1893BF, 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.
ICS1893BF, Rev. E, 8/11/09
August, 2009
Copyright © 2009, IDT, Inc.
All rights reserved.
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