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ML6691CQ Datasheet(PDF) 6 Page - Micro Linear Corporation |
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ML6691CQ Datasheet(HTML) 6 Page - Micro Linear Corporation |
6 / 10 page ML6691 6 FUNCTIONAL DESCRIPTION To describe the function of the ML6691, the device is separated into three sections, the Transmit Section, the Receive Section, and the Management section. Each section is discussed below. TRANSMIT SECTION The transmit section is responsible for converting transmit nibble data on the MII lines from the MAC into encoded and ciphered transmit symbols, as shown in Figure 1. The nibble input register samples the transmit nibble data on the MII lines and passes the nibble data onto the encoder. The encoder then converts the data to 4B/5B code (see Table 1) under the direction of the state machine. The state machine detects the leading edges of transmit enable and impresses the start of frame delimiter — the JK pair — ignoring the TXD<3:0> during these two symbol times. If, while transmit enable is asserted, the transmit error is asserted, the H symbol will be impressed except during the time the JK pair is emitted. Following the trailing edge of transmit enable, the end of frame delimiter — the TR pair — is generated, after which the IDLE symbol is generated to fill the space between frames. The encoded data is then enciphered by performing a XOR with the output of the cipher register. The cipher register is a linear feedback shift register which generates the cipher bit stream which is used to scramble the transmit symbol data. The Boolean algebra expression is listed below. TCFR11 = TCFR6 TCFR10 = TCFR5 TCFR9 = TCFR4 TCFR8 = TCFR3 TCFR7 = TCFR2 TCFR6 = NOT (TCFR11 OR TCFR10 OR TCFR9 OR TCFR8 OR TCFR7 OR TCFR6 OR TCFR5 OR TCFR4 OR TCFR3 OR TCFR2) OR TCFR1 TCFR5 = TCFR11 XOR TCFR9 TCFR4 = TCFR10 XOR TCFR8 TCFR3 = TCFR9 XOR TCFR7 TCFR2 = TCFR8 XOR TCFR6 TCFR1 = TCFR7 XOR TCFR5 The enciphered data are then passed to the symbol output register which drives the generated symbol data out to the PMD transceiver. Collision detect is implemented by noting the occurrence of reception during transmission. A linkfail indication at any time causes an immediate transition to the IDLE state and supersedes any other transmit operation. Figure 1. Transmit Section Block Diagram HEX/4B SYMBOL/5B HEX/4B SYMBOL/5B 0000 11110 J 11000 0001 01001 K 10001 0010 10100 T 01101 0011 10101 R 00111 0100 01010 H 00100 0101 01011 IDLE 11111 0110 01110 0111 01111 1000 10010 1001 10011 1010 10110 1011 10111 1100 11010 1101 11011 1110 11100 1111 11101 Table 1. 4B/5B Encoding Table TRANSMIT ERROR (TXER) LINK FAIL TRANSMIT STATE MACHINE ENCODER/ ENCIPHER SYMBOL OUTPUT REGISTER CARRIER AND COLLISION DETECT NIBBLE INPUT REGISTER CIPHER REGISTER TRANSMIT NIBBLE CLOCK (TXCLK) TRANSMIT ENABLE (TXEN) TRANSMIT SYMBOL CLOCK (TXC) TRANSMIT NIBBLE DATA (TXD[3:0]) TRANSMIT SYMBOL DATA (TSM[4:0]) RECEIVING TRANSMITTING COLLISION (COL) CARRIER SENSE (CRS) |
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