MEMORY ACCESS SYSTEM FOR MULTI-WINDOW CONTROL

摘要

PURPOSE:To update a picture at a high speed and to reduce the cost by constituting a window memory necessitating a large capacity, of a memory of a low speed, and constituting only a frame buffer storing a display data of a one-line portion, of a memory of a high speed. CONSTITUTION:Between a window memory 5 and a display 9, a frame buffer 7 of a one-line portion or above is provided. That is, the frame buffer 7 is brought to a random access by designating an address from a controller 6, and brought to an access serially from a CRT controller 8. It is constituted of a dual port memory to which a simultaneous access from both of them can be executed. The CRTC 8 starts serial read-out from the frame buffer 7 by taking advantage of a horizontal synchronizing signal generated by a horizontal line generating device 11. In this case, it will suffice that the window memory can execute an access at a low speed, and it will suffice that only the frame buffer 7 of a small quantity can execute an access at a high speed. In such a way, a picture plane can be updated at a high speed, and the cost can be reduced.