Digital circuit for addition and subtraction e.g. for cash till - has arrays of flip=flip stages providing inputs to processing circuit, with numbers input from right to left so that digits with value one are keyed in first

摘要

The digital electronic control circuit has an arithmetic stage that can be switched between addition and subtraction modes. The circuit receives inputs in the form of a series of four bit binary numbers and these are handled in input loading stages. The input stages are in the form of the arrays of flip-flops (16, 18) that combine with a further array. The flip-flops receive serially-entered numbers and outputs connect with the processor. ADVANTAGE - Avoids need for shift register.