Tools and techniques for teaching microprocessor software development

Abstract

AbstractDebugging low level language software can be a difficult business—the bare microprocessor lacks the user interface; facilities, such as simulators, provided on another machine can be tedious to use on running or partially working programs. A resolution of this difficulty lies in the harmonious use of a mainframe‐based debugging system and a real microprocessor.This paper describes tools and techniques for the development of low level software for the Intel 8080 microprocessor employing both simulated and real microprocessors. The debugging system allows the user to set up a virtual microprocessor into which programs can be loaded and run and from which a flexible tracing of the executing program can be obtained. The debugging system is built into a general purpose multi‐access operating system and this approach makes it possible to provide the system cheaply to a large number of users. Additionally, users have access to all the general facilities (such as editors) provided by the operating system itself.The system has been implemented on a minicomputer with 60 VDU terminals all of which can be used for interaction with the 8080 simulator or for general interactions with the mainframe operating system. The system has also been implemented in a self‐simulating version to run on a real Intel 8080 microprocessor. Many of the VDUs on the minicomputer are controlled by Intel 8080 microprocessors and it is possible to load and run large Intel 8080 programs which were assembled (and tested) on the mainframe or run the self simulator based debugging system. In this way a range of complementary debugging environments is provided: the simulator on the mainframe with its access to backing store (and, hence, the ability to save trace information), the self simulator on the microprocessor (with its better performance for the single user), and the actual Intel 8080 itself. The user can easily move a partially tested program between environments and thus use the environment which best suits his current phase of testing.