Queue control apparatus including memory to save data received when

Abstract

An overflow control unit stores, in a FIFO buffer, data generated by a processor. The overflow control unit sets a predetermined flag, upon detecting that a FIFO buffer is full or nearly full. The overflow control unit stores, in a saving buffer, data sent from the processor, while the flag is set. Thereafter, the overflow control unit notifies the processor, by an interrupt, of an effect that an available capacity of the FIFO buffer rises above a predetermined threshold. Upon receiving an interrupt, the processor transfers to the FIFO buffer data saved in the saving buffer. Upon a completion of transferring to the FIFO buffer all data saved in the saving buffer, the processor resets the flag. This allows the overflow control unit to again store in the FIFO buffer, data sent from the processor. The overflow control unit also monitors the volume of data stored in the saving buffer, and notifies the processor, by an interrupt, of an effect that the saving buffer is full. Upon receiving an interrupt, the processor expands an available capacity of the saving buffer.