THERMAL HEAD-DRIVING CIRCUIT

PURPOSE:To eliminate the need for changing a hardware construction when the number of heat generating resistors is changed due to a change in design or the like, by providing a means for supplying selection data as to whether individual ones of MXN heat generating resistors are to be driven, M times with N bits as a unit, and a means capable of variably setting the value of M according to a program. CONSTITUTION:A thermal head unit 4 comprises a heat generating resistor part 1 consisting of, for example, 320 heat generating resistors, a driver 2 and a data register 3, and a value of '40' is preliminarily set on a programmable counter 7 by a data signal 10. A count signal 17 from the counter 7 counts the number of times of rise in a write signal 11. The count signal is brought to a high level at the time of the first rise in the write signal 11, and is brought to a low level on counting to the set value '40' according to a program. Then, a data request circuit 16 from a data-requesting circuit 8 is brought to a low level, thereby inhibiting transfer of data. When the 40th data transfer is finished and 320 bits of printing data are stored into the register 3, a printing driving signal 18 is inputted to drive the driver 2.