Image-capable interprocessor link communications protocol

Claim 1

In an image-capable communications system having first and second processor connected by an interprocessor link, said first and second processors including a communication module, a plurality of higher level service modules, and one or more lower level modules connectable to said communication module and to a physical communication channel, an image communication protocol method for transferring image data from one of said processors (sender) to the other (receiver), comprising the steps of: (a) prior to transferring image data, establishing a line of communication by executing a three-way handshake to exchange status information between the sender and receiver; (b) when transferring image data initiated by the sender processor, the sender communication module executing the steps of, (1.) receiving from a higher level service module a user specified buffer address, buffer size and time out period for completing the transfer of date, (2.) initiating a timer for a period equal to one-half the user specified time out period; (3.) if a ready indication is received from a lower level module prior to time out of the timer, transmitting the data in the specified buffer over the link; (4.) if the timer times out prior to receipt of a ready indication, or prior to completion of the transmission of the data in the specified buffer address, initiating a timer for the remainder of the user specified time out period, and sending a ready to send message to the receiver; if a clear to send message is received from the receiver, waiting for a ready indication, and restarting data transmission when the ready indication is received, (5.) if the entire user specified time out period expires prior to completing the transmission, returning a time out error signal to a higher level service module in the sender processor; (c) when transferring image data initiated by the receiver processor, the receiver communication module executing the steps of, (1.) receiving a user specified buffer address, buffer size and time out period for completing the transfer of data from higher level service module, (2.) initiating a timer for a period equal to one-half the user specified time out period, (3.) indicating readiness to receive data, and attempting to fill the user specified buffer with data from the sender, (4.) if the timer times out before the specified buffer is filled, starting a timer for the remaining user timeout period and sending a ready to receive command, after receiving a clear to receive command from the sender, restarting the attempt to fill the buffer, (5.) if the entire user specified time out period expires without obtaining a clear to receive command and completing the data transfer, returning a time out error to a higher level service module in the receiver processor.