32-bit VGA Controllers - Accessing Shared Memory

If the same physical memory device is used for both processing code and video data storage, connection to the memory should be made through an appropriately configured bus arbitration component:

• On an OpenBus System Document – an Arbiter component.

• On a Schematic document – a Wishbone Dual Master or Wishbone Multi-Master component.

To avoid screen glitches caused by the video pipeline being starved of data, the arbitration component must be set to give higher priority to requests from the 32-bit VGA Controller.

For an example OpenBus System design that uses an Arbiter component to share access to a single physical memory device between a 32-bit processor and a memory-based VGA32_TFT Controller, see Catering for Memory-Based Peripherals.