Digital data processing device

Abstract

A digital data processing device in which a color memory has a temporal data storage register at input/output interface thereof so that the data write-in or data read-out operations executed by a micro-processing unit (MPU) is always performed through the temporal storage register. When data read-out or write-in operation is made to a character memory at a certain address, the same operation is simultaneously carried out for the color memory at the corresponding address. Assuming that MPU reads out a certain display address of a display screen, a corresponding character code is fetched by MPU from the character memory, while the corresponding color code is transferred to the temporal storage register from the color memory. When MPU performs the write-in operation for another address of the display screen, the character code held by MPU until then is written in the character memory at a designated address, while the color data i.e. the contents currently held by the temporal storage register are written in the color memory at the address which corresponds to the designated address of the character memory. In this manner, the color data is simultaneously transferred through the software-based processing for transferring only the character code in appearance, whereby the transfer of the contents to be displayed on the display screen can be carried out with an enhanced efficiency.