ICS1893CF Data Sheet - Release
Chapter 6 Functional Blocks
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
ICS1893CF, Rev. J, 08/11/09
August, 2009
Copyright © 2009, Integrated Device Technology, Inc.
All rights reserved.
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