Importance

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Abstract

An apparatus and method for loading a replacement computer program into a data encryption device having a central processing unit and a memory. The central processing unit is responsive to interrupt requests and operatively connected to a communications port. The memory has memory locations, and is partitioned into a data memory space and a program memory space, with the program memory space being read-only. The replacement computer program has a main entry point, and a load address which is the memory location at which the replacement computer program is to be loaded. When the occurence of an interrupt request, indicating a request to load the replacement computer porgram into the memory, is detected, the execution of a loaded computer program at a memory location is interrupted. Control is transferred to an interrupt routine. The replacement computer program is received through the communications port, and stored in the memory. The replacement computer program replaces the loaded computer program. Before storing the replacement computer program, the memory is partititoned so that the load address is in the data memory space, and after storing the replacement computer program, the memory is partititioned so that the load address is in the program memory space. Upon completion of the interrupt routine, control is transferred from the interrupt routine to the main entry point of the replacement computer program such that the interrupt routine does not return to the interrupted memory location.

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First Claim