ICS1893 Datasheet, PDF (69/152 Pages) Integrated Circuit Systems – 3.3-V 10Base-T/100Base-TX Integrated PHYceiver™

ICS1893 - Release
Chapter 8 Management Register Set
8.3.6 IEEE Reserved Bits (bits 1.10:7)
The IEEE reserves these bits for future use. When an STA:
• Reads a reserved bit, the ICS1893 returns a logic zero.
• Writes a reserved bit, the STA must use the default value specified in this data sheet.
Both the ISO/IEC standard and the ICS1893 reserve the use of some Management Register bits. ICS uses
some reserved bits to invoke ICS1893 test functions. To ensure proper operation of the ICS1893, an STA
must maintain the default value of these bits. Therefore, ICS recommends that an STA write the default
value to all reserved bits during all Management Register write operations.
Reserved bits 1.10:7 are Command Override Write (CW) bits. When bit 16.15, the Command Register
Override bit, is logic:
• Zero, the ICS1893 prevents all STA writes to CW bits.
• One, an STA can modify the value of these bits.
8.3.7 MF Preamble Suppression (bit 1.6)
Status Register bit 1.6 is the Management Frame (MF) Preamble Suppression bit. The ICS1893 sets bit 1.6
to inform the STA of its ability to receive frames that do not have a preamble. When this bit is logic:
• Zero, the ICS1893 is indicating it cannot accept frames with a suppressed preamble.
• One, the ICS1893 is indicating it can accept frames that do not have a preamble.
Although the ICS1893 supports Management Frame Preamble Suppression, its default value for bit 1.6 is
logic zero. This default value ensures that bit 1.6 is backward compatible with the ICS1890, which does not
have this capability. As the means of enabling this feature, the ICS1893 implements bit 1.6 as a Command
Override Write bit, instead of as a Read-Only bit as in the ICS1890. An STA uses the bit 1.6 to enable MF
Preamble Suppression in the ICS1893. [See the description of bit 16.15, the Command Override Write
Enable bit, in Section 8.11, “Register 16: Extended Control Register”.]
8.3.8 Auto-Negotiation Complete (bit 1.5)
An STA reads bit 1.5 to determine the state of the ICS1893 auto-negotiation process. The ICS1893 sets
the value of this bit using two criteria. When its Auto-Negotiation sublayer is:
• Disabled, the ICS1893 sets bit 1.5 to logic zero.
• Enabled, the ICS1893 sets bit 1.5 to a value based on the state of the Auto-Negotiation State Machine.
In this case, it sets bit 1.5 to logic one only upon completion of the auto-negotiation process. This setting
indicates to the STA that a link is arbitrated and the contents of Management Registers 4, 5, and 6 are
valid. For details on the auto-negotiation process, see Section 7.2, “Functional Block: Auto-Negotiation”.
Bit 1.5 is a latching high (LH) bit. (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”.)
Note: An Auto-Negotiation Restart does not clear an LH bit. However, performing two consecutive reads
of this register provides the present state of the bit.
ICS1893 Rev C 6/6/00
Copyright © 2000, Integrated Circuit Systems, Inc.
All rights reserved.
69
June, 2000