18-bit Sine/Cosine Function

SINCOS_X calculates the sine and cosine of an angle in radians. It has a fully pipelined architecture and uses fixed-point mathematics throughout. Input values are accepted as 18-bit signed values in the range -π to π. Output values are 17-bit signed values in the range -1 to 1. For input values outside the specified range, sin_out defaults to 0 and cos_out defaults to -1.

Input and output values are specified in [18 15] format with 1 sign bit, 2 integer bits and 15 fraction bits. Output values are in [17 15] format with 1 sign bit, 1 integer bit and 15 fraction bits. Internally, the function uses a quarter-wave SIN function core implemented as a 2nd order polynomial with dynamic coefficients. Values are sampled on the rising clock-edge of clk when en is high. The function has a 5 clock-cycle latency.

• Key Design Features
• Synthesizable, technology independent VHDL Core
• Combined functions y = sin(x), y = cos(x)
• Input range -π ≤ x ≤ π
• Output range -1 ≤ y ≤ 1
• Based on a quadratic polynomial with dynamic coefficients
• Input values as 18-bit signed fractions in radians
• Output values as 17-bit signed fractions
• Accurate to within 0.00017
• High-speed fully pipelined architecture
• Tiny implementation
• Only 5 clock-cycles latency

• Fixed-point mathematics
• Quadrature signal generation in digital communications
• Cheaper alternative to using a 65k x 16-bit LUT (128kbytes)
• Cheaper alternative to CORDIC