PURPOSE: To reduce overhead due to the switching of processing in a data souce and to improve processing performance by providing the control of a data input request signal with hysteresis characteristics.

CONSTITUTION: The value of a temporary storage residual counter 401 is compared with the upper limit value 403 and lower limit value 406 of a temporary storage residual by an upper limit comparator 402 and a lower limit comparator 405 and whether the residual exceeds the upper limit 403 or the lower limit 403 is judged. When the residual exceeds the upper limit value 403 at first from the state less than the lower limit value 406, a data input request generating part 404 inverts the polarity of a data input request signal 307 and temporarily stops data supply from a data souce. When the data souce is temporarily stopped after inverting the polarity of the signal 307, the data souce stopped state is held until the lower limit value is exceeded at first. Thereby even when the temporary storage residual is changed around the upper limit value 403 and the lower limit value 406 or finely changed between both the limit values, the polarity of the signal 307 is not frequently changed.