ICS1893CF datasheet(30/126 Pages) ICST

30 / 126 page

ICS1893CF, Rev. F, 03/01/07

Mar. 2007

Chapter 6 Functional Blocks

ICS1893CF Data Sheet - Release

6.3.3 PCS/PMA Transmit Modules

Both the PCS and PMA sublayers have Transmit modules.

6.3.3.1 PCS Transmit Module

The ICS1893CF PCS Transmit module accepts nibbles from the MAC Interface and converts the nibbles

into 5-bit ‘code groups’ (referred to here as ‘symbols’). In addition, the PCS Transmit module performs a

parallel-to-serial conversion on the symbols, and subsequently passes the resulting serial bit stream to the

PMA sublayer.

The first 16 nibbles of each MAC Frame represent the Frame Preamble. The PCS replaces the first two

nibbles of the Frame Preamble with the Start-of-Stream Delimiter (SSD), that is, the symbols /J/K/. After

receipt of the last Frame nibble, detected when TX_EN = FALSE, the PCS appends to the end of the Frame

an End-of-Stream Delimiter (ESD), that is, the symbols /T/R/. (The ICS1893CF PCS does not alter any

other data included within the Frame.)

The PCS Transmit module also performs collision detection. In compliance with the ISO/IEC specification,

when the transmission and reception of data occur simultaneously and the ICS1893CF is in:

• Half-duplex mode, the ICS1893CF asserts the collision detection signal (COL).

• Full-duplex mode, COL is always FALSE.

6.3.3.2 PMA Transmit Module

The ICS1893CF PMA Transmit module accepts a serial bit stream from its PCS and converts the data into

NRZI format. Subsequently, the PMA passes the NRZI bit stream to the Twisted-Pair Physical Medium

Dependent (TP-PMD) sublayer.

The ICS1893CF PMA Transmit module uses a digital PLL to synthesize a transmit clock from the Clock

Reference Interface.

6.3.4 PCS/PMA Receive Modules

Both the PCS and PMA sublayers have Receive modules.

6.3.4.1 PCS Receive Module

The ICS1893CF PCS Receive module accepts both a serial bit stream and a clock signal from the PMA

sublayer. The PCS Receive module converts the bit stream from a serial format to a parallel format and

then processes the data to detect the presence of a carrier.

When a link is in the idle state, the PCS Receive module receives IDLE symbols. (All bits are logic one.)

Upon receiving two non-contiguous zeros in the bit stream, the PCS Receive module examines the

ensuing bits and attempts to locate the Start-of-Stream Delimiter (SSD), that is, the /J/K/ symbols.

Upon verification of a valid SSD, the PCS Receive module substitutes the first two standard nibbles of a

Frame Preamble for the detected SSD. In addition, the PCS Receive module uses the SSD to begin

framing the ensuing data into 5-bit code symbols. The final PCS Receive module performs 4B/5B decoding

on the symbols and then synchronously passes the resulting nibbles to the MAC Interface.

The Receive state machine continues to accept PMA data, convert it from serial to parallel format, frame it,

decode it, and pass it to the MAC Interface. During this time, the Receive state machine alternates between

Receive and Data States. It continues this process until detecting one of the following:

• An End-of-Stream Delimiter (ESD, that is, the /T/R/ symbols)

• An error

• A premature end (IDLEs)

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