Direct access to slave processing by unprotected application using context saving and restoration

Claim 1

A computer system providing a plurality of user applications concurrently running on a host processor direct access to a slave processor comprising: an input buffer including a separately addressable nonprotected buffer and protected buffer, such that it is the nonprotected buffer and not the protected buffer into which communications from any of the plurality of user applications are written; an output buffer; means for sending a context save request to the protected buffer of said input buffer when processing in the host processor switches from one of the plurality of user applications to another of the plurality of user applications; means, in said slave processor, for writing in said output buffer a save frame of data words representing partially completed requests sufficient to describe the internal dynamic state of the slave processor for the user application currently communicating with the slave processor upon recognizing the context save request in the protected buffer of said input buffer; and means, in said slave processor, for restoring the internal dynamic state of the slave processor by loading the save frame for a next user application to communicate with the slave processor into said input buffer and executing the data words in the save frame.