ICS1893 datasheet(49/152 Pages) ICST

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Chapter 7

Functional Blocks

ICS1893 Rev C 6/6/00

June, 2000

ICS1893 - Release

7.4.4

100Base-TX Operation: Adaptive Equalizer

The ICS1893 has a TP-PMD sublayer that uses adaptive equalization circuitry to compensate for signal

amplitude and phase distortion incurred from the transmission medium. At a data rate of 100 Mbps, the

transmission medium (that is, the cable) introduces significant signal distortion because of high-frequency

attenuation and phase shift. The high-frequency loss occurs primarily because of the cable skin effect that

causes the conductor resistance to rise as the square of the frequency rises.

The ICS1893 has an adaptive equalizer that accurately compensates for these losses in shielded

twisted-pair (STP) and unshielded twisted-pair (UTP) cables. The DSP-based adaptive equalizer uses a

technique that compensates for a wide range of cable lengths. The optimizing parameter for the

equalization process is the overall bit error rate of the ICS1893. This technique closes the loop on the entire

data reception process and provides a very high overall reliability.

7.4.5

100Base-TX Operation: Twisted-Pair Transmitter

The ICS1893 uses the same Twisted-Pair Transmit pins (TP_TXP and TP_TXN) for both 10Base-T and

100Base-TX operations. Each twisted-pair transmitter module is a current-driven, differential driver that

can supply either of the following:

• A two-level 10Base-T (that is, Manchester-encoded) signal

• A three-level 100Base-TX (that is, MLT-3 encoded) signal

The ICS1893 interfaces with the medium through an isolation transformer (sometimes referred to as a

magnetic module). The ICS1893’s transmitter uses wave-shaping techniques to control the output signal

rise and fall times (thereby eliminating the need for external filters) and interfaces directly to the isolation

transformer.

Note:

In reference to the ICS1893, the term ‘Twisted-Pair Transmitter’refers to the set of Twisted-Pair

Transmit output pins (TP_TXP and TP_TXN).

For information on the 10Base-T Twisted-Pair Transmitter, see Section 7.5.11, “10Base-T Operation:

Twisted-Pair Transmitter”.

7.4.6

100Base-TX Operation: Twisted-Pair Receiver

The ICS1893 uses the same Twisted-Pair Receive pins (TP_RXP and TP_RXN) for both 10Base-T and

100Base-TX operations. The internal twisted-pair receiver modules interface with the medium through an

isolation transformer. The 100Base-TX receiver module accepts and processes a differential three-level

100Base-TX (that is, MLT-3 encoded) signal from the isolation transformer. (In contrast, the 10Base-T

receiver module accepts and processes a differential two-level, Manchester- encoded, 10Base-T signal

from the isolation transformer).

Note:

In reference to the ICS1893, the term ‘Twisted-Pair Receiver’refers to the set of Twisted-Pair Receive

output pins (TP_RXP and TP_RXN).

For information on the 10Base-T Twisted-Pair Receiver, see Section 7.5.12, “10Base-T Operation:

Twisted-Pair Receiver”.

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