ICS1893 datasheet(42/152 Pages) ICST

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ICS1893 Rev C 6/6/00

June, 2000

Chapter 7

Functional Blocks

ICS1893 Data Sheet - Release

7.2.4

Auto-Negotiation: Reset and Restart

If enabled, execution of the ICS1893 auto-negotiation process occurs at power-up and upon management

request. There are two primary ways to begin the Auto-Negotiation state machine:

• ICS1893 reset

• Auto-Negotiation Restart

7.2.4.1

Auto-Negotiation Reset

During a reset, the ICS1893 initializes its Auto-Negotiation sublayer modules to their default states. (That

is, the Auto-Negotiation Arbitration State Machine and the Auto-Negotiation Progress Monitor reset to their

idle states.) In addition, the Auto-Negotiation Progress Monitor status bits are all set to logic zero. This

action occurs for any type of reset (hardware reset, software reset, or power-on reset).

7.2.4.2

Auto-Negotiation Restart

As with a reset, during an Auto-Negotiation restart, the ICS1893 initializes the Auto-Negotiation Arbitration

State Machine and the Auto-Negotiation Progress Monitor modules to their default states. However, during

an Auto-Negotiation Restart, the Auto-Negotiation Progress Monitor status bits maintain their current state.

Only three events can alter the state of the Auto-Negotiation Progress Monitor status bits after a Restart:

(1) an STA read operation, (2) a reset, or (3) the Auto-Negotiation Arbitration State Machine progressing to

a higher state or value.

The Auto-Negotiation Progress Monitor Status bits change only if they are progressing to a state with a

value greater than their current state (that is, a state with a higher logical value than that of their current

state). For a detailed explanation of these bits and their operation, see Section 7.2.5, “Auto-Negotiation:

Progress Monitor”.

After the Auto-Negotiation Arbitration State Machine reaches its final state (which is Auto-Negotiation

Complete), only an STA read of the QuickPoll Detailed Status Register or an ICS1893 reset can alter these

status bits.

Any of the following situations initiates a restart of the ICS1893 Auto-Negotiation sublayer:

• A link failure

• In software mode:

– Writing a logic one to the Control Register’s Restart Auto-Negotiation bit (bit 0.9), which is a self-

clearing bit.

– Toggling the Control Register’s Auto-Negotiation Enable bit (bit 0.12) from a logic one to a logic zero,

and back to a logic one.

• In hardware mode:

– Toggling the ANSEL (Auto-Negotiation Select) pin from a logic one to a logic zero, and back to a

logic one.

7.2.5

Auto-Negotiation: Progress Monitor

Under typical circumstances, the Auto-Negotiation sublayer can establish a connection with the ICS1893’s

remote link partner. However, some situations can prevent the auto-negotiation process from properly

achieving this goal. For these situations, the ICS1893 has an Auto-Negotiation Progress Monitor to provide

detailed status information to its Station Management (STA) entity. With this status information, the STA

can diagnose the failure mechanism and – in some situations – establish the link by correcting the problem.

When enabled, the auto-negotiation process typically requires less than 500 ms to execute, independent of

the link partner's ability to perform the auto-negotiation process. Typically, an STA polls both the

Auto-Negotiation Complete bit (bit 1.5) and the Link Status bit (bit 1.2) to determine when a link is

successfully established, either through auto-negotiation or parallel detection. The STA can then poll the

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