A bidirectional shift register includes multi-stages of shift register
unit circuits that transmit a start pulse in a direction indicated by a
logical level of a transmission direction control signal. Each of the
shift register unit circuits has a first transfer gate that transmits the
start pulse in synchronization with one of a clock signal and an inverted
clock signal, which is obtained by inverting the clock signal, a second
transfer gate that transmits the start pulse in synchronization with the
other signal of the clock signal and the inverted clock signal, a first
logical circuit that inverts an input signal and outputs the inverted
signal, and first and second clocked inverters that are exclusively valid
according to the logical level of the transmission direction control
signal. An output terminal of the first logical circuit is connected to
input terminals of the first and second clocked inverters, and output
terminals of the first and second clocked inverters are connected to an
input terminal of the first logical circuit through the first and second
transfer gates.