Samsung KS8910, User Manual

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100BASE-TX DIGITAL BLOCKS KS8910 100/10 Mbps ETHERNET TRANSCEIVER
4-2
Preliminary Spec. ver
1.4
PHYSICAL MEDIUM ATTACHMENT SUBLAYER (PMA)
The PMA provides a medium-independent means for the PCS and other bit-oriented clients to support the use of a
range of physical media. The KS8910’s PMA performs the following functions:
• Mapping of transmit and receive code-bits between the PMA’s client and the underlying PMD
• Generating a control signal indicating the availability of the PMD to a PCS or other client and synchronizing
with Auto-Negotiation
• Scrambling and descrambling of the transmit code-bits and the receive code-bits, respectively.
• Conversion of the scrambled transmit code-bits from NRZ to NRZI and reverse for the receive code-bits.
PHYSICAL MEDIUM DEPENDENT SUBLAYER (PMD)
The KS8910’s PMD receives NRZI code-bits from the PMA, encodes them into MLT-3, and transmits them to the
adjacent PMD over the physical link. The PMD also decodes the incoming bits and delivers them to the PMA in
NRZI format. Furthermore, the PMD recovers the clock from the incoming data bits. The PMD block is an Analog
Block.
DESCRIPTION OF OPERATION
Transmit operation
Data for transmission is received in nibbles by the PCS over the MII. The PCS then converts each nibble into a 5-
bit code-group which is serialized and forwarded to the PMA. The PMA scrambles the serialized bit stream and
converts it from NRZ to NRZI before it is forwarded to the PMD.The PMD converts the NRZI formatted outgoing bit
stream into MLT-3.
The first half of the above described data flow is illustrated in the Figure 4-1.
Receive operation
The incoming bit stream transmitted by the remote PMD through the physical link is received in MLT-3 format. The
PMD converts it into an NRZI formatted bit stream and then recovers the clock as well as data. The data stream is
changed into NRZ format by the PMA which also descrambles it. The PCS then looks for a Start-of-Stream Delimit,
SSD, in the incoming data stream, locks to it and converts it into 5-bit code-groups in parallel format. Each code-
group is, thereupon, translated into it’s corresponding 4-bit group and transmitted nibblewise over the MII which is
partly shown in Figure 4-1.