ICS1893AFLF datasheet(49/136 Pages) IDT

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Chapter 7

Functional Blocks

ICS1893AF, Rev. D 10/26/04

October, 2004

ICS1893AF Data Sheet - Release

Note:

An ICS1893AF receives ‘valid data’ when its Twisted-Pair Receiver phase-locked loop can acquire lock

and extract the receive clock from the incoming data stream for a minimum of three consecutive bit

times.

When a link is invalid and the Link Monitor Function detects the presence of data, the ICS1893AF does

not transition the link to the valid state until after the reception of the present packet is complete.

Enabling or disabling the Smart Squelch Function affects the Link Monitor function.

A transition from the invalid state to the valid state does not automatically update the latching-low Link

Status bit.

7.5.6

10Base-T Operation: Smart Squelch

The Smart Squelch Function imposes more stringent requirements on the Link Monitor Function regarding

the definition of a valid link, thereby providing a level of insurance that spurious noise is not mistaken for a

valid link during cable installation.

An STA can control the execution of the ICS1893AF Smart Squelch Function using bit 18.0 (the Smart

Squelch Inhibit bit in the 10Base-T Operations Register). When bit 18.0 is logic:

• Zero (the default), an ICS1893AF enables its Smart Squelch Function. In this case, the Link Monitor

must confirm the presence of both data and a valid IDL at the end of the packet before declaring a link

valid.

• One, an ICS1893AF disables or inhibits its Smart Squelch Function. In this case, the Link Monitor does

not have to confirm the presence of an IDL to declare a link valid (that is, the reception of any data is

sufficient).

In 10Base-T mode, an ICS1893AF appends an IDL to the end of each packet during data transmission.

The receiving PHY (that is, the remote link partner) sees this IDL and removes it from the data stream.

7.5.7

10Base-T Operation: Carrier Detection

The ICS1893AF has a 10Base-T Carrier Detection Function that establishes the state of its Carrier Sense

signal (CRS), based upon the state of its Transmit and Receive state machines. These functions indicate

whether the ICS1893AF is (1) transmitting data, (2) receiving data, or (3) in a collision state (that is, the

ICS1893AF is both transmitting and receiving data on its twisted-pair medium, as defined in the ISO/IEC

8802-3 standard). When the ICS1893AF is configured for:

• Half-duplex operations, the ICS1893AF asserts its CRS signal when either transmitting or receiving data.

• Full-duplex operations (or when it is in Repeater mode), the ICS1893AF asserts its CRS signal only

when it is receiving data.

7.5.8

10Base-T Operation: Collision Detection

The ICS1893AF has a 10Base-T Collision Detection Function that establishes the state of its Collision

Detection signal (COL) based upon both (1) the state of its Receiver state machine and (2) the state of its

Transmit state machine. When the ICS1893AF is operating in:

• Half-duplex mode, the ICS1893AF asserts its COL signal to indicate it is receiving data while

transmission of data is also in progress.

• Full-duplex mode, the ICS1893AF always sets its COL signal to FALSE.

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