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LAN9252I/ML 数据表(PDF) 123 Page - Microchip Technology |
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LAN9252I/ML 数据表(HTML) 123 Page - Microchip Technology |
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123 / 329 page  2015 Microchip Technology Inc. DS00001909A-page 123 LAN9252 11.2.2.3 Scrambler and PISO Repeated data patterns (especially the IDLE code-group) can have power spectral densities with large narrow-band peaks. Scrambling the data helps eliminate these peaks and spread the signal power more uniformly over the entire channel bandwidth. This uniform spectral density is required by FCC regulations to prevent excessive EMI from being radiated by the physical wiring. The seed for the scrambler is generated from the PHY address, ensuring that each PHY will have its own scrambler sequence. For more information on PHY addressing, refer to Section 11.1.1, "PHY Addressing". The scrambler also performs the Parallel In Serial Out conversion (PISO) of the data. 11.2.2.4 NRZI and MLT-3 Encoding The scrambler block passes the 5-bit wide parallel data to the NRZI converter where it becomes a serial 125MHz NRZI data stream. The NRZI is then encoded to MLT-3. MLT-3 is a tri-level code where a change in the logic level represents a code bit “1” and the logic output remaining at the same level represents a code bit “0”. 11.2.2.5 100M Transmit Driver The MLT-3 data is then passed to the analog transmitter, which drives the differential MLT-3 signal on output pins TXPx and TXNx, to the twisted pair media across a 1:1 ratio isolation transformer. The transmitter drives into the 100 imped- ance of the CAT-5 cable. Cable termination and impedance matching require external components. 11.2.2.6 100M Phase Lock Loop (PLL) The 100M PLL locks onto the reference clock and generates the 125 MHz clock used to drive the 125 MHz logic and the 100BASE-TX Transmitter. 00110 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 11001 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 00000 /P/ INVALID INVALID 00001 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 00010 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 00011 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 00101 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 01000 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 01100 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID 10000 /V/ INVALID, MII Receive Error (RXER) if during MII Receive Data Valid (RXDV) INVALID TABLE 11-1: 4B/5B CODE TABLE (CONTINUED) Code Group Sym Receiver Interpretation Transmitter Interpretation |
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