Abstract: A signal generator generates a plurality of grey level signals which are inputted into a one bit-per-pixel raster scan video display device (such as a simple matrix liquid crystal display). Each grey level signal causes a particular proportion of pixels to be illuminated, in order to produce a particular grey level. Uniform high quality grey levels are produced by introducing into each grey level signal a variable frame phase shift for successive rows of each frame. The specific phase shifts introduced between successive rows and frames result in the illuminated pixels being distributed evenly in each frame. The pattern of illuminated pixels changes smoothly with time to produce the required uniform high quality grey level.

Abstract: A data processing apparatus and method are described in which a CPU is operable in either a main processing mode (User32) or an exception processing mode (e.g. FIQ32). The CPU has a plurality of main data registers (R0 to R15) and a processing status register (CPSR) for use in the main processing mode. Upon entering the exception processing mode at least one exception data register (R8fiq to R14fiq) is substituted for use in place of a respective corresponding one of the main data registers and the data held within the processing status register is stored within a saved processing status register (SPSRfiq). When the exception processing mode is left, the main data registers are returned for use in place of the exception data registers and the data stored within the saved processing status register is restored to the processing status register. A plurality of exception processing modes are described each having their own associated exception data registers.