Patent ID: 7159002

Claim:
A method of performing a sequence of infinite impulse response digital filters, comprising the steps of: in a first instance of the filter, executing a series of operations comprising: sequentially multiplying a current input data value, and first and second previous input data values, with corresponding ones of a first set of filter coefficients, using a multiplier; sequentially multiplying first and second previous intermediate data values with corresponding ones of the first set of filter coefficients, using the multiplier; and sequentially accumulating products from each multiplying operation into an accumulator; in a second instance of the filter, executing a series of operations comprising: in a same clock cycle as a next to last one of the sequential accumulating operations, multiplying the second previous intermediate data value with a corresponding one of a second set of filter coefficients, using the multiplier; in a next clock cycle, then loading the contents of the accumulator into a shadow store and multiplying the contents of the accumulator with a corresponding one of the second set of filter coefficients, using the multiplier; then clearing the accumulator; sequentially multiplying the first previous intermediate data value with a corresponding one of a second set of filter coefficients, and multiplying first and second previous output data values with corresponding ones of the second set of filter coefficients; and then sequentially accumulating products from each multiplying operation in the second instance of the filter in the accumulator; and storing the contents of the shadow store in memory.