To obtain a higher update rate of drawing a display image data after subjected to a rotation processing by carrying out in parallel a transfer processing of the display image data and the rotation processing of the display image data.

An image display system has a liquid crystal controller 200 including: a host IF 240 that writes the display image data transferred from a display data generating device 300 into a RAM 210; and a rotation processing unit 250 that rotates the display image data on the RAM 210. The liquid crystal controller 200 controls the host IF 240 such that the display image data transferred from the display data generating device 300 is written in the RAM 210 at timing of starting the rotation processing of the display image data by the rotation processing unit 250. Thereby, the rotation processing and the transfer processing of the display image data can be carried out parallel.

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