ICS1893 datasheet(18/152 Pages) ICST

18 / 152 page

ICS1893 Rev C 6/6/00

June, 2000

Chapter 4

Overview of the ICS1893

ICS1893 Data Sheet - Release

4.1

100Base-TX Operation

During 100Base-TX data transmission, the ICS1893 accepts packets from a MAC/repeater and inserts

Start-of-Stream Delimiters (SSDs) and End-of-Stream Delimiters (ESDs) into the data stream. The

ICS1893 encapsulates each MAC/repeater frame, including the preamble, with an SSD and an ESD. As

per the ISO/IEC Standard, the ICS1893 replaces the first octet of each MAC preamble with an SSD and

appends an ESD to the end of each MAC/repeater frame.

When receiving data from the medium, the ICS1893 removes each SSD and replaces it with the

pre-defined preamble pattern before presenting the nibbles to its MAC/Repeater Interface. When the

ICS1893 encounters an ESD in the received data stream, signifying the end of the frame, it ends the

presentation of nibbles to its MAC/Repeater Interface. Therefore, the local MAC/repeater receives an

unaltered copy of the transmitted frame sent by the remote MAC/repeater.

During periods when MAC frames are being neither transmitted nor received, the ICS1893 signals and

detects the IDLE condition on the Link Segment. In the 100Base-TX mode, the ICS1893 transmit channel

sends a continuous stream of scrambled ones to signify the IDLE condition. Similarly, the ICS1893 receive

channel continually monitors its data stream and looks for a pattern of scrambled ones. The results of this

signaling and monitoring provide the ICS1893 with the means to establish the integrity of the Link Segment

between itself and its remote link partner and inform its Station Management Entity (STA) of the link status.

For 100M data transmission, the ICS1893 MAC/Repeater Interface can be configured to provide either a

100M Media Independent Interface (MII) or a 100M Symbol Interface. With the Symbol Interface

configuration, the data stream bypasses the ICS1893 Physical Coding sublayer (PCS). In addition:

The ICS1893 shifts the responsibility of performing the 4B/5B translation to the MAC/repeater. As a

result, the requirement is for a 5-bit data path between the MAC/repeater and the ICS1893.

The latency through the ICS1893 is reduced. (The ICS1893 provides this 100M Symbol Interface

primarily for repeater applications for which latency is a critical performance parameter.)

4.2

10Base-T Operation

During 10Base-T data transmission, the ICS1893 inserts only the IDL delimiter into the data stream. The

ICS1893 appends the IDL delimiter to the end of each MAC frame. However, since the 10Base-T preamble

already has a Start-of-Frame delimiter (SFD), it is not required that the ICS1893 insert an SSD-like

delimiter.

When receiving data from the medium (such as a twisted-pair cable), the ICS1893 uses the preamble to

synchronize its receive clock. When the ICS1893 receive clock establishes lock, it presents the preamble

nibbles to its MAC/Repeater Interface. The 10M MAC/Repeater Interface can be configured as either a

10M MII, a 10M Serial Interface, or a Link Pulse Interface.

In 10M operations, during periods when MAC frames are being neither transmitted nor received, the

ICS1893 signals and detects Normal Link Pulses. This action allows the integrity of the Link Segment with

the remote link partner to be established and then reported to the ICS1893’s STA.

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