Abstract: An image-sensor emulating device establishing a link with a host system via the internal bus of the host system. The image-sensor emulating device emulates the functions of image-sensors by programmably generating the relevant image-sensor and timing signals. Alternatively, the timing signals can also be generated from the timing signals outputted by an outside image-sensor. Therefore, the emulating device can generate predetermined image-sensor signals and timing signals such that the debugging process is simplified and the developing efficiency is improved. Moreover, the emulating device according to the present invention can also generate a timing signal serving as a reference timing signal for emulating an image-sensor. The reference timing signal can be used to compare with the actual timing signals of an image-sensor.