In displaying image data received from a camera module on a display device such as a view finder, image data having a size suited for display from an image size conversion circuit is displayed via line memories included in a signal-for-display generation circuit. Vertical synchronization in an image data storage including these line memories is established by initializing a reading address in accordance with a frame head pixel indication and a reading completion indication of one line in the line memories. It is possible to reduce power consumption of an image display system for displaying an image of a imaging subject.