The design and construction of a microprocessor- based educational computer

Abstract

Since digital computers came into widespread use in the early 1960's there has been the need to educate Engineers and Scientists in the areas of logic, machine organisation and programming. The computer described is aimed primarily at the teaching of machine organisation while offering useful facilities in the other areas. In the past, machines demonstrating computer architecture have been special purpose machines, they are now rather dated and have proved to be very expensive. The new machine uses a microprocessor to simulate the operation of an educational computer in which the content of all registers and states of gates are simultaneously displayed. The computer has an order code and architecture which is typical of modern small computers and has four modes of operation, viz:- 'Manual' in which individual parts of the machine can be manipulated manually by push buttons. 'One bit' in which the machine will obey an instruction one-step at a time and return to manual mode on completion of the instruction. 'One Instruction' when the machine will carry out the sequence of steps forming an instruction at a selected speed and will return to manual mode on completion of the instruction. 'Continuous' in which the machine obeys sequential instructions taken from the store until it is stopped manually or reaches a 'halt' instruction when it returns to manual mode. While such a computer could be a specially built machine as in the past, use of a microprocessor reduces the display to a series of lamps and push buttons interfaced to the processor and the apparent operation of the computer is determined by the program held in Read-only memory. Thus changes in the architecture of the order code of the educational computer can be achieved by re-writing part or all of the program and it is therefore anticipated that the machine described will be capable of enhancement both easily and cheaply.