A method of frame synchronization serial data transmission. A transmitting circuit
in a data communication apparatus converts frame data into serial data and transmit
the same, and following the serial data, the transmitting circuit transmits frame
synchronization data varying several times in the interval from an edge of a clock
signal to an edge of the next clock signal; a receiving circuit receives the frame
data and detects twice or more variations in the same interval to find out the
end of the frame data, by receiving the serial data from a signal lines, serial
data is transmitted while carrying out frame synchronization.