Direct memory read and cell transmission apparatus for ATM cell segmentation system

A direct memory and cell transmission apparatus for an ATM cell segmentation system having a function for receiving a data from a host memory and forming an ATM cell, comprising:

• a segmentation circuit for reading/writing an information from a local memory, interpreting the information, and extracting identifying information used for combining the information and the cell used for the DMA;
• and
• a DMA read and cell combining circuit for receiving the identifying information used for the DMA and information used for the cell combining operation from the segmentation circuit, performing a DMA reading operation, generating a cell using the data transmitted from the host memory and used for the cell combining operation and transferring to the segmentation circuit, said DMA read and cell combining circuit including,
• a DMA request transfer and PCI buffer read circuit for receiving a DMA request, transferring the request to the PCI circuit, and reading host data from a buffer in the PCI circuit when the host data is inputted from the host memory;
• a word alignment circuit for receiving word data from the DMA request transfer and PCI buffer read circuit, and an offset and size information of a predetermined byte, extracting a predetermined byte used for a cell configuration and aligning the word data;
• a cell FIFO unit for receiving the aligned word data from the word alignment circuit;
• a cell transmission circuit for receiving a cell transmission or DMA completion request instruction from the DMA request transfer and PCI buffer read circuit, reading the aligned word data received from the cell FIFO unit, and multiplexing a cell header, trailer and CRC value to form a cell.

A direct memory read and cell transmission apparatus for an ATM cell segmentation system having a PCI interface unit and a cell segmentation circuit, comprising,

• a read controller, coupled to said PCI interface unit and to said cell segmentation circuit, for requesting a PCI memory read using a start address and byte size from a host memory;
• an alignment unit for extracting predetermined bytes from word unit data transferred from said PCI interface unit, said alignment unit including,
• a shifting unit, coupled to said PCI interface unit, for receiving and shifting input data from said PCI interface unit;
• an alignment controller, coupled to said read controller and to said shifting unit, for receiving an enable signal, an offset signal and a byte size from said read controller, said alignment controller for computing information used to determine whether a new word is formed and for computing and controlling an amount of data shifted by said shifting unit;
• a word generator, coupled to said shifting unit and to said alignment controller, for outputting word data using an output signal from said shifting unit and in accordance with a control signal received from said alignment controller;
• a residue data generator, coupled to said shifting unit and to said alignment controller, for outputting a residue data of a next cycle using an output signal from said shifting unit;
• a storing unit, coupled to said alignment controller, said word generator and said residue data generator, for storing a residue data from the residue data generator in accordance with a control signal from said alignment controller;
• and
• a latching unit, coupled to said alignment controller and to said word generator, for latching word data received from the word generator and for providing an output in accordance with a control signal from said alignment controller;
• a cell FIFO unit coupled to said alignment unit for receiving the output from said latching unit and, in response to a write signal from said alignment unit, for storing aligned word data to said FIFO unit;
• and
• a cell transmitter coupled to said PCI interface unit, said cell segmentation circuit, said alignment unit, and said cell FIFO, said cell transmitter providing a read signal to said cell FIFO for outputting said stored data.