ICS1892 Datasheet, PDF (43/148 Pages) Integrated Circuit Systems – 10Base-T/100Base-TX Integrated PHYceiver

ICS1892
Chapter 7 Functional Blocks
7.3.4 PCS/PMA Receive Modules
Both the PCS and PMA sublayers have Receive modules.
7.3.4.1 PCS Receive Module
The ICS1892 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/Repeater 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/Repeater Interface. During this time, the Receive state machine
alternates between the Receive and Data States and continues this process until detection of one of the
following:
• An End-of-Stream Delimiter (ESD, that is, the /T/R/ symbols)
• An error
• A premature end (IDLEs)
Upon receipt of an ESD, the Receive state machine returns to the IDLE state without passing the ESD to
the MAC/Repeater Interface. Detection of an error forces the Receive state machine to assert the receive
error signal (RX_ER) and wait for the next symbol. If the ICS1892 Receive state machine detects a
premature end, it forces the assertion of the RX_ER signal, sets the Premature End bit (bit 17.5) to logic
one, and transitions to the IDLE State.
ICS1892, Rev. D, 2/26/01
© 2000-2001, Integrated Circuit Systems, Inc.
All rights reserved.
43
February 26, 2001