In a method and an arrangement for controlling printing by a thermotransfer printing apparatus with relative movement between a thermotransfer print head and a print medium, a microprocessor that provides pixel energy data to a pixel energy memory by making an energy value calculation and by coding, and a print data controller prepares the pixel energy data by decoding during the printing in a number (corresponding to the pixel energy value) of binary pixel data each with the same binary value. The print data controller includes at least one pixel energy data preparation unit, a DMA controller, an address generator, a printer controller and a phase counter. The DMA controller allows an access to the pixel energy data stored in the pixel energy memory as code in order to provide the pixel energy data in print columns to the at least one pixel energy data preparation unit. The address generator generates addresses for selection of the buffered code during each phase of a number of phases. The phase counter supplies a phase count value to a phase data preparation unit in which the code value A and phase count value B are compared in order to generated binary pixel data, which are serially supplied from the output D to at least one shift register of the thermotransfer print head.