PURPOSE: To automate data writing and control by controlling a data selector with the output of a flip-flop and timing pulses obtained by counting a clock and replacing data with serial data, and reading the status of FIFO in the flip-flop at the timing of a read of data from the FIFO.

CONSTITUTION: A decoder 5 decodes the output 110 of a counter 4 and the data selector 3 is switched at specific timing when the flip-flop 6 is in a set state. The data selector is operated as mentioned above to select and output serial data 109 obtained by converting output data 107 of the FIFO 1 by a p/s converting circuit instead of serial data 103 only at the specific timing. Further, the decoder 5 resets the counter 4 with a signal 113 and also supplies a clock 112 to the p/s converting circuit 2 when the output 110 of the counter 4 reaches a specific value.