Abstract: A coefficient data transfer processing method for a digital signal processor which has a coefficient address pointer independent of a program counter, whereby a processing program and coefficient data are transferred and supplied from a microcomputer determination, whether an instruction is a read instruction of the coefficient data to execute a read cycle steal or with is made; a value of a program counter with is made; when it is the read instruction, new coefficient data is transferred from the microcomputer to a transfer buffer at an instruction read stage and instruction decode stage in a processing unit; and the coefficient data stored in the transfer buffer is written into a coefficient data memory by the read cycle steal at an execute stage in the same processing unit.

Abstract: A digital signal processor (DSP) computes logarithmic values for data values of the input signal by using an approximation formula expanded into power series. To reduce the number of computing steps, the processor includes a shift circuit for shifting an input data value into a predetermined range of numeric values, a high-order coefficient memory for storing coefficient values of high order coefficients other than a zero-order coefficient of the approximation formula for data values within the predetermined range of numeric values, a zero-order coefficient memory for storing a coefficient value of the zero-order coefficient shifted according to the number of digits shifted by the shift circuit, and an address specifying circuit for specifying a reading address of the zero-order memory corresponding to the number of digit shifted by the shifted circuit. Also, a DSP computes an inverse logarithmic value of a data value of the input signal by using an approximation formula expanded into power series.