ICS1893AGLF datasheet(47/135 Pages) ICST

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Chapter 7 Functional Blocks

ICS1893AG, Rev. A 04/14/05

April, 2005

ICS1893AG Data Sheet - Preliminary

7.5.4 10Base-T Operation: Idle

An ICS1893AG transmits Normal Link Pulses (that is, 10Base-T Idles) on its MDI in the absence of data (that

is, when the MAC/repeater is not requiring it to transmit any data). During this time the link is Idle, and the

ICS1893AG periodically transmits link pulses at a rate of one link pulse every 16 ms in compliance with the

ISO/IEC 8802-3 standard. In 10Base-T mode, the ICS1893AG continues transmitting link pulses even while

receiving data. This situation does not generate a Collision Detect signal (COL) because link pulses indicate

an idle state for a link.

7.5.5 10Base-T Operation: Link Monitor

When an ICS1893AG is in 10Base-T mode, its Link Monitor Function observes the data received by the

10Base-T Twisted-Pair Receiver to determine the link status. The results of this continual monitoring are

stored in the Link Status bit. The Station Management entity (STA) can access the Link Status bit in either

the Status Register (bit 1.2) or the QuickPoll Detailed Status Register (bit 17.0).

When the Link Status bit is:

• Zero, either a valid link is not established or the link is momentarily dropped since either the last read of

the Link Status bit or the last reset of the ICS1893AG.

• One, a valid link is established.

The ICS1893AG Link Status bit is a latching low (LL) 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”.)

The criteria used by the Link Monitor Function to declare a link either valid (that is, ‘established’ or ‘up’) or

invalid (that is, ‘failed’ or ‘down’) depends upon these factors: the present state of the link, whether its

Smart Squelch function is enabled, and the incoming data.

When the 10Base-T link is:

• Invalid, and the Smart Squelch function is:

– Disabled (bit 18.0 is logic one), the Link Monitor Function must detect at least one of the following

events before transitioning its link from the invalid state to the valid state:

• More than seven, ISO/IEC-defined, Normal Link Pulses (NLPs)

• Any valid data

– Enabled (bit 18.0 is logic zero), the Link Monitor Function must detect at least one of the following

events before transitioning its link from the invalid state to the valid state:

• More than seven, ISO/IEC-defined, Normal Link Pulses (NLPs)

• Any valid data followed by a valid IDL

• Valid, and the Smart Squelch function is:

– Disabled (bit 18.0 is logic one), the Link Monitor Function continues to report its link as valid as long

as it continues to detect any of the following:

• ISO/IEC-defined, Normal Link Pulses (NLPs)

• Any valid data

– Enabled (bit 18.0 is logic zero), the Link Monitor Function continues to report its link as valid as long

as it continues to detect any of the following:

• ISO/IEC-defined, Normal Link Pulses (NLPs)

• Any valid data followed by a valid IDL

• Valid, the Link Monitor Function declares the link as invalid if it receives neither data nor NLPs (that is,

the link shows either no activity or inconsistent activity) for more than 81 to 83 ms. In this case the Link

Monitor Function sets the Link Status bit to logic zero.

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