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Electronic Components Datasheet Search |
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DM9006 Datasheet(PDF) 68 Page - Davicom Semiconductor, Inc. |
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DM9006 Datasheet(HTML) 68 Page - Davicom Semiconductor, Inc. |
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68 / 76 page 
DM9006 2-port Switch with Processor Interface 68 Preliminary datasheet DM9006-13-DS-P01 September 1, 2009 9.3.2.8 Code Group Alignment The Code Group Alignment block receives un-aligned 5B data from the descrambler and converts it into 5B code group data. Code Group Alignment occurs after the J/K is detected and subsequent data is aligned on a fixed boundary. 9.3.2.9 4B5B Decoder The 4B5B Decoder functions as a look-up table that translates incoming 5B code groups into 4B (Nibble) data. When receiving a frame, the first 2 5-bit code groups receive the start-of-frame delimiter (J/K symbols). The J/K symbol pair is stripped and two nibbles of preamble pattern are substituted. The last two code groups are the end-of-frame delimiter (T/R Symbols). The T/R symbol pair is also stripped from the nibble, presented to the Reconciliation layer. 9.3.3 10Base-T Operation The 10Base-T transceiver is IEEE 802.3u compliant. When the DM9006 is operating in 10Base-T mode, the coding scheme is Manchester. Data processed for transmit is presented in nibble format, converted to a serial bit stream, then the Manchester encoded. When receiving, the bit stream, encoded by the Manchester, is decoded and converted into nibble format. 9.3.4 Collision Detection For half-duplex operation, a collision is detected when the transmit and receive channels are active simultaneously. Collision detection is disabled in full duplex operation. 9.3.5 Carrier Sense Carrier Sense (CRS) is asserted in half-duplex operation during transmission or reception of data. During full-duplex mode, CRS is asserted only during receive operations. 9.3.6 Auto-Negotiation The objective of Auto-negotiation is to provide a means to exchange information between linked devices and to automatically configure both devices to take maximum advantage of their abilities. It is important to note that Auto-negotiation does not test the characteristics of the linked segment. The Auto-Negotiation function provides a means for a device to advertise supported modes of operation to a remote link partner, acknowledge the receipt and understanding of common modes of operation, and to reject un-shared modes of operation. This allows devices on both ends of a segment to establish a link at the best common mode of operation. If more than one common mode exists between the two devices, a mechanism is provided to allow the devices to resolve to a single mode of operation using a predetermined priority resolution function. Auto-negotiation also provides a parallel detection function for devices that do not support the Auto-negotiation feature. During Parallel detection there is no exchange of information of configuration. Instead, the receive signal is examined. If it is discovered that the signal matches a technology, which the receiving device supports, a connection will be automatically established using that technology. This allows devices not to support Auto-negotiation but support a common mode of operation to establish a link. |
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