 |
 |
|
| ICS1893CFI |
|
|||||||||||||||||
 IDT
|
| |||||||||||||||||
|
52 page 
ICS1893CF, Rev. J, 08/11/09 August, 2009 52 Chapter 7 Management Register Set ICS1893CF Data Sheet - Release Copyright © 2009, Integrated Device Technology, Inc. All rights reserved. 7.3.6 IEEE Reserved Bits (bits 1.10:7) The IEEE reserves these bits for future use. When an STA: • Reads a reserved bit, the ICS1893CF 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 ICS1893CF reserve the use of some Management Register bits. ICS uses some reserved bits to invoke ICS1893CF test functions. To ensure proper operation of the ICS1893CF, 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 ICS1893CF prevents all STA writes to CW bits. • One, an STA can modify the value of these bits. 7.3.7 MF Preamble Suppression (bit 1.6) Status Register bit 1.6 is the Management Frame (MF) Preamble Suppression bit. The ICS1893CF 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 ICS1893CF is indicating it cannot accept frames with a suppressed preamble. • One, the ICS1893CF is indicating it can accept frames that do not have a preamble. Although the ICS1893CF 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 ICS1893CF 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 ICS1893CF. [See the description of bit 16.15, the Command Override Write Enable bit, in Section 7.11, “Register 16: Extended Control Register”.] 7.3.8 Auto-Negotiation Complete (bit 1.5) An STA reads bit 1.5 to determine the state of the ICS1893CF auto-negotiation process. The ICS1893CF sets the value of this bit using two criteria. When its Auto-Negotiation sublayer is: • Disabled, the ICS1893CF sets bit 1.5 to logic zero. • Enabled, the ICS1893CF 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 6.2, “Functional Block: Bit 1.5 is a latching high (LH) bit. (For more information on latching high and latching low bits, see Section 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. |
|
