To inspect memory while avoiding bank competitions.

In an image display system, a display device has two display modes: a back monitor mode which displays a photographic image and a navigation mode which displays a navigation image that is a non-photographic image other than a photographic image. An image writing part 61 periodically writes a photographic image in a writing bank in the back monitor mode and the navigation mode. In addition, an image reading part 62 periodically reads a photographic image from a reading bank which is different from the writing bank in the back monitor mode only. On the other hand, a memory inspection part 63 inspects a bank to be inspected which is different from the writing bank in the navigation mode only. Since the memory inspection part 63 can select the bank to be inspected without taking the reading bank into consideration, therefore, the memory inspection part 63 can inspect a frame memory 45 while avoiding bank competitions.