LAN9211 datasheet(70/147 Pages) SMSC

70 / 147 page

High-Performance Small Form Factor Single-Chip Ethernet Controller with HP Auto-MDIX Support

Datasheet

Revision 2.9 (03-01-12)

SMSC LAN9211

DATASHEET

4.3.4

Descrambling

The descrambler performs an inverse function to the scrambler in the transmitter and also performs

the Serial In Parallel Out (SIPO) conversion of the data.

During reception of IDLE (/I/) symbols. the descrambler synchronizes its descrambler key to the

incoming stream. Once synchronization is achieved, the descrambler locks on this key and is able to

descramble incoming data.

Special logic in the descrambler ensures synchronization with the remote PHY by searching for IDLE

symbols within a window of 4000 bytes (40us). This window ensures that a maximum packet size of

1514 bytes, allowed by the IEEE 802.3 standard, can be received with no interference. If no IDLE-

symbols are detected within this time-period, receive operation is aborted and the descrambler re-starts

the synchronization process.

The descrambler can be bypassed by setting bit 0 of register 31.

4.3.5

Alignment

The de-scrambled signal is then aligned into 5-bit code-groups by recognizing the /J/K/ Start-of-Stream

Delimiter (SSD) pair at the start of a packet. Once the code-word alignment is determined, it is stored

and utilized until the next start of frame.

4.3.6

5B/4B Decoding

The 5-bit code-groups are translated into 4-bit data nibbles according to the 4B/5B table. The SSD,

/J/K/, is translated to “0101 0101” as the first 2 nibbles of the MAC preamble. Reception of the SSD

causes the PHY to assert the internal RX_DV signal, indicating that valid data is available on the

Internal RXD bus. Successive valid code-groups are translated to data nibbles. Reception of either the

End of Stream Delimiter (ESD) consisting of the /T/R/ symbols, or at least two /I/ symbols causes the

PHY to de-assert the internal carrier sense and RX_DV.

These symbols are not translated into data.

4.4

10Base-T Transmit

Data to be transmitted comes from the MAC layer controller. The 10Base-T transmitter receives 4-bit

nibbles from the MII at a rate of 2.5MHz and converts them to a 10Mbps serial data stream. The data

stream is then Manchester-encoded and sent to the analog transmitter, which drives a signal onto the

twisted pair via the external magnetics.

The 10M transmitter uses the following blocks:

MII (digital)

TX 10M (digital)

10M Transmitter (analog)

10M PLL (analog)

4.4.1

10M Transmit Data across the internal MII bus

The MAC controller drives the transmit data onto the internal TXD BUS. When the controller has driven

TX_EN high to indicate valid data, the data is latched by the MII block on the rising edge of TX_CLK.

The data is in the form of 4-bit wide 2.5MHz data.

4.4.2

Manchester Encoding

The 4-bit wide data is sent to the TX10M block. The nibbles are converted to a 10Mbps serial NRZI

data stream. The 10M PLL locks onto the external clock or internal oscillator and produces a 20MHz

LAN9211 数据表(PDF) 70 Page - SMSC Corporation

LAN9211 数据表(HTML) 70 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载