A Programmed Variable-Rate Counter for Generating the Sine Function

The sine curve is approximated by a set of straight line segments whose slopes are chosen to be integral multiples of a binary fraction. A programmed counter counts up or down at a rate proportional to the slope, thus generating an approximate sine function. Using (360/256)≈1.4 degree intervals and four integral slopes, ±0(1/128), ±1(1/128), ±2(1/128), ±3(1/128), the maximum difference between the true and the generated value is 0.014 and occurs at 36.6 degrees. The extension of this method to higher accuracy and to other functions is indicated.