ML6691 データシートの表示（PDF） - Micro Linear Corporation

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ML6691

100BASE-T MII-to-PMD Transceiver

Micro Linear Corporation 

RECEIVE SECTION

The receive section is responsible for converting received

unaligned symbols into deciphered, aligned and decoded

nibble data on the MII lines, as shown in Figure 2. The

receive symbol input register samples the receive symbol

data from the PMD transceiver and passes the symbol data

onto the decipher process. The cipher lock is restored by

reloading the decipher register after detecting 13

consecutive IDLE symbols which must occur between

packets. The decipher function is then performed by an

exclusive-OR of the output of the decipher register and

the input symbols.

The decipher symbol data are then passed to the symbol

aligner. The symbols are broken into arbitrary five-bit

groups. The alignment is achieved by scanning the code-

bit stream for the JK pair following the idle symbols.

ML6691

The decoder translates the 4B/5B coded deciphered and

aligned symbols into hex nibbles. The decoder along with

the state machine also examines the symbol stream for

packet framing information. The JK is converted back to

55 and the TR into 00. The decoder also flags invalid

symbol codes and generates the receive error signal. The

state machine also generates the receive data valid signal.

A premature stream termination is caused by the detection

of two IDLE symbols prior to an TR. A linkfail signal will

also terminate the receive operation immediately.

Note, the “Bad SSD” state is not implemented in the

receive state machine of the ML6691.

RECEIVE SYMBOL DATA

(RSM[4:0])

SYMBOL INPUT

REGISTER

DECIPHER

RECEIVE SYMBOL

CLOCK

(RXC)

DECIPHER LOCK

SUBSECTION

LINK

FAIL RECEIVING

RECEIVE

STATE MACHINE

RECEIVE RECEIVE

ERROR DATA VALID

(RXER) (RXDV)

SYMBOL ALIGNER

DECODER

NIBBLE OUTPUT

REGISTER

RECEIVE NIBBLE DATA

(RXD[3:0])

RECEIVE NIBBLE CLOCK

(RXCLK)

Figure 2. Receive Section Block Diagram

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