Abstract: A display subsystem supports both normal mode and portrait mode displays. In normal mode, the scan starts at the upper left comer of the display. In portrait mode, the scan starts at the lower left comer of the display. The display subsystem includes a dual mapped display memory having a normal mode display area and a portrait mode display area. The portrait mode display area is defined by X-ofst(Virtual) and Y-ofst. X-ofst(Virtual) is a power of two that is greater than the real X-ofst supported by the display in portrait mode. Address requests from the CPU or software use high order bits to specify whether the address is in the normal or portrait mode display area. In addition, address requests to the portrait mode display area use the address space defined by X-ofst(Virtual) and Y-ofst. When the address request specifies the portrait mode display area, the address of the request is translated to account for the different mode of the display.

Abstract: An application specific integrated circuit (ASIC) has a clock controller that dynamically selects an appropriate clock frequency for a resource. The ASIC includes a central processing unit (CPU), on-chip memory, a memory controller controlling external memory devices, a system bus, and various peripheral controllers. Devices that can be accessed by other devices, such as the on-chip memory, the memory controller, and the system bus are “resources.” The devices that access the resources are “controllers.” The ASIC generates a master clock and the clock controller derives clocks for driving the resources and controllers from the master clock. A multiplexer (MUX) in the clock controller selects the clock that is passed to a resource. Each controller has a request line to the clock controller for signaling when the controller is accessing a resource.