JPS5776650A - Loop counter control system - Google Patents

Abstract

PURPOSE:To vary the number of times of internal looping according to the number of times of external looping of double loop regarding autocorrelation arithmetic, by adding the readout output of a read-only memory and the contents of a loop counter by an adding circuit and by setting the sum in the loop counter. CONSTITUTION:For arithmetic shown by expression (1), a frequency i=c+n-d of internal looping should be varied with a frequency n=a-b of external looping. With an instruction LS (loop start), the readout output a-b+M of a ROM is set in a loop counter LPC and also set as a frequency of looping in a stack ST. With every instruction LE (loop end), the LPC is increased in contents to return to the starting LS or LSM (loop start modify) of a loop and when the contents of the LPC have a maximum value M, the contents of the ST are set in the LPC. When the control returns to the LSM, the readout output c-d+b of the ROM and the contents of the LPC are added by an adding circuit ADD, whose sum output is set in the LPC through a selector SEL2.