Virtual contiguous fifo having the provision of packet-driven automatic

Abstract

An endian domain conversion circuit for converting data packets transmitted between two bus interfaces. The novel system advantageously eliminates any requirement for a large bit switch within the circuit's write data path. Instead, endian conversion intelligence is placed into the read data path. Double words (dwords) are individually received from an incoming data packet and bytes are parallel stored into the same byte location of several different first-in-first-out (FIFO) memories. In one example, the dwords are 32-bits each and the number FIFO memories used is four. An entire input data packet is received in this manner, incrementing the write address of the FIFO memories for each dword. Depending on the type of endian domain conversion required, if at all, endian conversion control circuitry of the present invention controls the manner in which the four exemplary FIFO memories are read (via a read pointer) and the manner which their data is supplied over the output bus to generate the output data. In one embodiment, a byte stream is generated over the output bus. Alternatively, dwords are sent over the output bus in proper endian domain format. Data descriptors located in a data packet header define the endian input domain format, the expected endian output domain format, the data packet size and the start address in system memory of the input data packet. The novel system is well suited to process arbitrarily sized data packets as well as data packets starting at arbitrary byte boundaries.