Circuit arrangement for comparing two binary numbers

摘要

1,111,626. Digital control systems. WERKZEUGMASCHINENFABRIK MAGDEBURG VEB. 4 March, 1966, No. 9721/66. Heading G4H. A circuit for determining the sign of the difference between two binary numbers representing a desired value and an actual value, and for indicating coincidence of the values comprises a plurality of binary stages 1, Fig. 1, a pulse generator 7 connected to the lowest order stage so as to periodically change the result of the comparison therein by an amount equal to the order of that stage, the output 6 from the highest stage being connected to a circuit adapted to distinguish between signals indicating that the sign of the difference is positive or negative, and a fluctuation between these conditions at the frequency of the pulse generator indicating that the desired and actual values are equal. The indicating device may be a lamp 8 which is unlit when the desired value is less than the actual value, flashes when they are equal, and burns continuously when the desired value is greater than the actual value. The binary stage chain by itself is arranged to produce no output when the difference is positive or zero. The input from pulse generator 7 makes the difference negative by one unit so that when the difference between the input numbers is actually zero there appears a periodic negative indication which causes the lamp to flash. The three signal conditions are separated by a circuit 10, shown in Fig. 2. The " 1 " output at 6, indicating that the desired value is greater than the actual, is passed by AND gate 12 to output 14 if there is no output from filter 16. The " 0 " signal is inverted at 11 and passes through AND gate 13 to output 15. The fluctuating signal passes through filter 16 where it is rectified and inverted to close both gates 12 and 13 so that no output is produced. The actual position may be controlled automatically by the comparator signal or by an operator guided by the indicator lamp 8.