LX-1 is an integrated circuit prototype of a microprocessor which is being used as a design vehicle to study the problems associated with the design and implementation of a similar computer constructed with large-scale integrated circuits. The organizational simplicity of LX-1 is emphasized and the supporting microprogramming and simulation facilities are discussed and examples are given.

A set of programs has been developed to aid in the design, testing, and documenting of logic circuits. The user can input logic descriptions by freehand sketching logic diagrams, or he can enter gate connectivity descriptions via a keyboard. Both input forms are then transformed into an internal data structure which can serve as input to logic simulation and test generation programs. Good documentation is encouraged by permitting easy editing and updating of drawings with a TX-2 graphics console which consists of a conventional oscilloscope and an input tablet. A Lincolnwriter is available for typed input and output.

Two procedures are presented for detecting and diagnosing arbitrary single-gate failures in combinational logic circuits. A gate is defined as any multiple-input single-output combinational circuit, and a failure is any detectable transformation of the correct gate function. The testing procedures do not require the construction of a fault table and will locate, to within an equivalence class, the faulty gate and describe its failure.

This paper is an introduction which presents only the first layer of the makeup of graphics. While this layer is explained sufficiently and clearly, as in many tutorial papers, value judgements are studiously avoided. The primary purpose, therefore, of this review will be to place in perspective some of the alternatives presented.