AV1890Y-14 View Datasheet(PDF) - Integrated Circuit Systems

Part Name

Description

Manufacturer

AV1890Y-14

10Base-T/100Base-TX Integrated PHYceiver™

Integrated Circuit Systems 

ICS1890

100Base-TX Physical Coding Sublayer [PCS]

Carrier Detector & Framer

The carrier detector examines the serial bit stream looking for

the SSD, the “JK” symbol pair. In the idle state, IDLE symbols

(all logic ones) will be received. If the carrier detector detects a

logic zero in the bit stream, it examines the following bits

looking for the first two non-contiguous zeros, confirms that

the first 5-bits form the “J” symbol (11000) and asserts carrier

detect. At this point the serial data is framed and the second

symbol is checked to confirm the “K” symbol (10001). If

successful, the following framed data (symbols) are presented

to the 4B5B decoder. If the “JK” pair is not confirmed, the false

carrier detect is asserted and the idle state is re-entered.

Collision Detector Collision is asserted in half-duplex

mode when transmission and data reception occur

simultaneously. In full duplex mode, collision is never asserted.

Parallel/Serial Converter

This block converts data between 5-bit symbols and 1-bit

serial data.

4B/5B Encoder/Decoder

When the ICS1890 is operating in the 100Base-TX mode,

4B5B coding is used. This coding scheme maps a 4-bit nibble

to a 5-bit code group. Since this gives 32 possible symbols

and the data only requires 16 symbols, 16 symbols are designated

control or invalid. The control symbols used are “JK” as the

start-of-stream delimiter (SSD), “TR” as the end-of-stream

delimiter (ESD), “I” as the IDLE symbol and “H” to signal an

error. All other symbols are invalid and, if detected, will set the

receive error bit in the status register.

When transmitting, nibbles from the MII are converted to 5-

bit code groups. The first 16 nibbles obtained from the MII are

the MAC frame preamble. The ICS1890 replaces the first two

nibbles with the start-of-stream delimiter (the “JK” symbol

pair). Following the last nibble, the ICS1890 adds the end-of-

stream delimiter (the “TR” symbol pair).

When receiving, 5-bit code groups are converted to nibbles

and presented to the MII. If the ICS1890 detects one or more

invalid symbols, it sets the receive error bit in the status

register. When receiving a frame, the first two 5-bit code

groups received are the start-of-stream delimiter (the “JK”

symbol pair), the ICS1890 strips them and substitutes two

nibbles of the normal preamble pattern. The last two 5-bit code

groups are the end-of- stream delimiter (the “TR” symbol

group), these are stripped from the nibbles presented to the

MAC.

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