A printing control unit for a thermal printer that prints by applying heat energy to a recording medium and is able to operate in multiple print modes, includes a line buffer unit, a shift register unit, and a configuration registration unit. The line buffer unit accumulates current dot printing data supplied from a host. The shift register unit gets and passes the current dot printing data and previous dot history data from the line buffer unit to a logic circuit unit. The configuration registration unit stores configuration data for setting data logic of the logic circuit unit.