System for controlling read and write streams in a circular fifo buffer

Abstract

A distributed digital imaging processing system having a number of processing units and circular FIFO buffers connected together using data transforming streams. Processing units read data from buffers using a transforming read streams. These read streams reorder the buffer data to form patches representing neighborhood pixels and may provide the same data multiple times. After processing a patch, a processing unit writes the resultant patch into a buffer using a transforming write stream which reorders the data into the storage format of the buffer. Several buffers can feed a single processor and one processor can feed several buffers. All the details of each data stream (buffer, current buffer location, patch size, access pattern) are stored in a table entry, along with a pointer to the data stream that it must follow in the buffer to avoid the hazards of reading and writing data out of order. In the case where a buffer has multiple read streams, requiring read streams to maintain a particular order reduces the work necessary to check for either a write or read hazard to comparing the location of a stream with it's leader. A single state machine computes from each table entry all addresses for all data transfers between the processors and buffers, and updates the table entry after each cycle. Since table entries define the streams which link processors to memory, communication paths between processors is completely under software control.