A shift register stores printing data in synchronism with a transfer clock. A
latch
circuit temporarily latches data having a predetermined number of bits to the shift
register in response to a data latch signal. A shift register stores block data
in synchronism with a transfer clock. A latch circuit temporarily latches data
having the predetermined number of bits to the shift register in response to a
block data latch signal. Each AND gate receives a block selection signal from a
printing block selection unit, a printing data selection signal corresponding to
a printing dot from a printing data supply unit, and an energization time selection
signal. An output from the AND gate turns on/off a switching transistor. As a result,
a heater is heated to discharge ink droplets.
