Method of sending data streams using a refetchable first-in-first-out memory which is read in a sequence that backs-up

Abstract

A stream of data words is sent from a memory thru a controller and an external data buffer to an I/O device by a method which includes the steps of: 1) transferring a segment of the stream of data from the memory into the controller while concurrently sending a subsegment of the segment from the controller thru the data buffer to the I/O device via a transmission burst in which the receipt of individual parts of the subsegment are not acknowledged by the I/O device; 2) receiving a signal in the controller from the I/O device at any time during the sending step, to terminate the transmission burst; 3) subsequently receiving a signal in the controller, from the I/O device, to restart the transmission burst beginning with a selectable part of the last subsegment that was sent; 4) removing from the controller, only the portion of the segment which precedes the selectable part of the subsegment; and, 5) repeating the above steps until the stream of data is received in its entirety by the I/O device. To perform the above steps, the controller includes a refetchable First-In-First-Out memory (RFIFO) into which the segments are written in a cyclic sequence and from which the subsegments are read in the same sequence except that read sequence backs up.