ICS1893CF datasheet(34/126 Pages) ICST

34 / 126 page

ICS1893CF, Rev. F, 03/01/07

Mar. 2007

Chapter 6 Functional Blocks

ICS1893CF Data Sheet - Release

6.4.6 100Base-TX Operation: Twisted-Pair Receiver

The ICS1893CF 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:

1. In reference to the ICS1893CF, the term ‘Twisted-Pair Receiver’ refers to the set of Twisted-Pair

Receive output pins (TP_RXP and TP_RXN).

2. For information on the 10Base-T Twisted-Pair Receiver, see Section 6.5.12, “10Base-T Operation:

Twisted-Pair Receiver”.

6.4.7 100Base-TX Operation: Isolation Transformer

The ICS1893CF interfaces with a medium through isolation transformers. The PHY requires two isolation

transformers: one for its Twisted-Pair Transmitter and the other for its Twisted-Pair Receiver. These

isolation transformers provide both physical isolation as well as the means for coupling a signal between

the ICS1893CF and the medium for both 10Base-T and 100Base-TX operations.

Note: For information on isolation transformers (also referred to as magnetic modules), see Section 5.3,

“Twisted-Pair Interface”.

6.5 Functional Block: 10Base-T Operations

When configured for 10Base-T mode, the ICS1893CF MAC Interface is configured to provide 10M MII

(Media Independent Interface). The Twisted-Pair Interface is automatically configured to provide a

two-level, Manchester-encoded signal at the voltage levels specified in the ISO/IEC standard. (For more

information on the Twisted-Pair Interface, see Section 5.3, “Twisted-Pair Interface”.)

The 10Base-T and 100Base-TX operations differ as follows. 10Base-T operations are fundamentally

simpler than 100Base-TX operations. The data rate is slower, requiring less encoding than 100Base-TX

operations. In addition, the bandwidth requirements (and therefore the line attenuation issues) are not as

severe as with 100-MHz operations. Consequently, when an ICS1893CF is set for 10Base-T operations, it

requires fewer internal circuits in contrast to 100Base-TX operations. (For an overview of 10Base-T

operations, see Section 4.6, “10Base-T Operations”.).

6.5.1 10Base-T Operation: Manchester Encoder/Decoder

During data transmission the ICS1893CF acquires data from its MAC Interface in 4-bit nibbles. The

ICS1893CF converts this data into a Manchester-encoded signal for presentation to its MDI, as required by

the ISO/IEC specification.

In a Manchester-encoded signal, all logic:

• Ones are:

– Positive during the first half of the bit period

– Negative during the second half of the bit period

• Zeros are:

– Negative during the first half of the bit period

– Positive during the second half of the bit period

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