Programmable frequency and duty cycle tone signal generator

Claim 1

Apparatus for generating an output signal having a controllable duty cycle and frequency comprising: first and second control means adapted for selectively generating respective first and second different multibit control words each representing the desired duration of a respective half-cycle of said output signal; oscillator means for generating a clock signal comprising a sequence of clock pulses; first and second presettable down counting means each having a clock input receiving said clock signal, a preset input receiving a respective one of said first and second control words from said first and second control means, an enable input and a load input, each of said first and second counting means further including a control output developing a control signal in response to the associated counting means assuming a zero count, the control output of each of said counting means being connected to its respective load input; bi-stable means having a set input, a reset input and an output; and circuit means coupling the load input and control output of said first counting means to the set input of said bi-stable means and the load input and control output of said second counting means to the reset input of said bi-stable means, said circuit means further coupling the output of said bi-stable means in non-inverted form to the enable input of one of said counting means and in inverted form to the enable input of the other of said counting means, whereby said output signal is developed in the form of a continuous succession of logically high and low signal states at the output of said bi-stable means.