Switching of programming routine supporting storage stacks

Abstract

A system in which a device or machine is controlled by instructions from a data processor is provided which minimizes main memory storage requirements. An interrupt service routine monitors the input to the processor received from the device in response to control instructions sent by the processor. The interrupt service routine monitors this response for exception conditions. When an exception condition indicating that the device is no longer capable of fully carrying out processor instructions is received by the interrupt service routine, it activates an exception handler routine. A primary memory storage stack normally supports the interrupt service routine. However, upon the activation of the exception handler routine, this primary storage stack is switched to support the exception handler routine, and a secondary stack of significantly lower storage capacity is placed in support of the interrupt service routine which should have lower purported storage requirements during the active period of the exception handler routine. This results in a substantial saving of main processor memory capacity which otherwise would have to be dedicated to the support of the two respective routines.