Driver copies to tx buffer initiates dma dma occurs

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• Driver copies to Tx buffer, initiates DMA. • DMA occurs to FIFO from Tx buffer. • After DMA , FIFO sends pkt on wire. After sending full pkt to wire NIC interrupts to Driver. • Driver updates pointers and stats.
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SUSHMA RAWAL 16 Transmit Logic • Adds preamble and start of frame delimiter to the beginning of the frame. • Calculates and adds CRC to the end of the frame • Handles the access protocol including automatic retransmission
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SUSHMA RAWAL 17 Transmit logic • Transmit data is sent from the FIFO, one byte at a time. • Preamble, SOF delimiter and CRC added to frame. • If the transmitter gets a FIFO empty status during transmission without also getting an End of Packet The transmitter remains stopped until the interrupt is cleared.
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SUSHMA RAWAL 18 Tx Errors • Tx FIFO Underrun: If FIFO is exhausted during transmission • Out of Window Collision • Tx Abort • Carrier Sense Lost • When packet txmitted to wire Tx OK or TxErr Interrupt can be generated.
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SUSHMA RAWAL 19 Receive • NIC gets packet in FIFO • Automatically DMAs to Rx Ring buffer with status bytes in front indic length and Rx status • After full pkt sent to Rx buffer NIC interrupts • Interrupt Routine copies from Rx buffer to socket buffer and informs network interface queue.
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SUSHMA RAWAL 20 Receive P C I I/ F Tx FIFO Rx FIFO Tx/Rx Logic INTERRUPT LOGIC & REG Pkt Disc
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SUSHMA RAWAL 21 Receiver Logic Functions • The receiver logic of the network interface performs the following: • Communicates the incoming data to the receiving FIFO. • Checks the destination address of the incoming frame. • Checks the CRC of the incoming frame. • Checks the length of the incoming frame.
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SUSHMA RAWAL 22 Data Transfer to Receiving FIFO • When receiver is enabled, the incoming data is transferred, to receiving FIFO. • Frame is
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Driver copies to Tx buffer initiates DMA DMA occurs to FIFO...

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