JPS648455A - Address forming circuit - Google Patents

Abstract

PURPOSE:To prevent processing time from being increased even if the degree of a finite impulse response (FIR) filter is not the second power by detecting that the contents of an address pointer indicate an area other than a memory area by a comparator for comparing the contents of a pointer obtained before the specification of operation and an independently prepared value. CONSTITUTION:An address forming circuit is constituted of an address pointer 11, an operation specifying circuit 12 corresponding to the pointer 11, an arithmetic circuit 13 for executing operation for the pointer 11 on the basis of the specification of the circuit 12, a register 14, a comparator 15 for comparing the contents of the pointer 11 with that of the register 14, a register 16, and a selecting circuit 17 for selecting either one of the result of the circuit 13 and the contents of the register 16 based on the specification of the circuit 12 and the comparing result of the comparator 15 and outputting the selected contents to the pointer 11. In this case, the circuit 17 is provided with a function for selecting the contents of the register 16 only when both the contents of the pointer 11 and the register 14 coincide with each other and increment is specified in the circuit 12 and outputting the selected contents to the pointer 11.