Errors building Clocked Video Output

Hi Andrew,

it will be better not to write the gui directly into the framebuffer memory, as framebuffer memory will be read continuously at output pixel clock rate for clocked video output. and writing the GUI(using Nios) to the framebuffer memory may cause clash of memory read/write operations and there might be data corruption as NIos will not be able to write the GUI fast enough as it is required by the clocked video output IP. so it will b better to write GUI to other memory buffer using nios and using SGDMA to transfer this to framebuffer memory in streaming format.