Input/output multiplexer security system

Abstract

An input/output processing system includes a plurality of active modules, a plurality of passive modules, at least one memory module and a system interface unit having a plurality of ports, each of which connect to a different one of the modules. The active modules include an input/output processing unit which processes interrupts and executes command signals and at least one multiplexer unit which directly controls transfers between the memory module and any one of a plurality of peripheral devices coupled to different ports of the multiplexer unit. The system interface unit operatively provides connections between different ones of the modules during the execution of commands included within user programs. The multiplexer unit includes sets of registers selectable under program control which store information which enables user programs for accessing the memory module. Additionally, other ones of these registers store control information used to control the processing of interrupts as well as other operations independently of user programs. The multiplexer unit includes apparatus which operatively couples these registers and is responsive to commands to ensure that only authorized acceses to these registers are made during system operation. The system also provides access rights to those registers to different types of system software such that only the system routines having the appropriate privileges are able to transfer information to those registers within the multiplexer unit.