Patent ID: 6870541

Claim:
A random access memory (RAM) incorporated display driver for displaying display data stored in the incorporated RAM on a display screen, comprising: a RAM configured to store the display data to be displayed on the display screen; a latch shift register configured to receive the display data read out from said RAM and if said display screen is intended to be scrolled in a horizontal direction, shift said read out display data depending on the scrolling direction and if said display screen is intended to be scrolled in a vertical direction, hold said read out display data; an access control circuit configured to read out the display data from said RAM, send the read out display data to said latch shift register, and if said display screen is intended to be scrolled in a horizontal direction, write back the display data shifted by said latch shift register into an original region in said RAM and if said display screen is intended to be scrolled in a vertical direction, write back the display data held by said latch shift register into a region in said RAM moved by the amount of the scroll from the original region of said RAM, and supply the written back display data in said RAM to said display screen according to a screen control signal supplied by a CPU configured outside of the display driver; and a selecting circuit configured to select a region in a horizontal direction capable of being scrolled in the display screen, wherein said access control circuit supplies display data in a region selected by said selecting circuit to said latch shift register.