Bus arbitration scheme for facilitating operation of a printing apparatus

In a printing apparatus of the type having a video processor adapted to transfer image data from an input device to a raster output scanning device, said video processor having an image data bus across which image data can be transmitted, said video processor comprising:

• a memory section, coupled with the image data bus, for storing image data transmitted thereto;
• a first buffering device, selectively coupled with the image data bus, for buffering image data transmitted from the input device to said memory section, said first buffering device being adapted to generate a request signal when seeking access to the image data bus;
• a second buffering device, selectively coupled with the image data bus, for buffering image data transmitted from said memory section to the raster output scanning device, said second buffering device being adapted to generate a request signal when seeking access to the image data bus, wherein the raster output scanning device is controlled by the output of said second buffering means;
• an arbiter, coupled with said first and second buffering devices, for arbitrating which of said first and second buffering devices are enabled to access the image data bus to transfer image data with said memory section when said arbitrator receives request signals from said first and second buffering devices concurrently;
• a charge retentive member;
• means for charging said charge retentive member, said raster output scanning device being adapted to selectively discharge a surface of said charge retentive member to form an intelligible pattern of charged and discharged areas on said charge retentive member;
• means for developing the intelligible pattern on said charge retentive member to form a developed pattern thereon;
• and
• means for transferring the developed pattern from said charge retentive member to a substrate.

A method for use in a printing apparatus of the type having a video processor adapted to transfer image data from an input device to an output device, said video processor having an image data bus across which image data can be transmitted, said video processor including a memory section disposed on the image data bus, the method comprising the steps of:

• transmitting image data generated by the input device to first means for buffering image data during a first preselected time interval, the first buffering means being operatively coupled to the input device and decoupled from the memory section;
• buffering the image data in the first buffering means during the first preselected time period;
• transmitting a first image data bus request signal from the first buffering means to means for arbitrating bus request signals after the first preselected time period has elapsed;
• transmitting image data buffered in second means for buffering image data from the second buffering means to the output device during a second preselected time interval, the second buffering means being operatively coupled to the output device and decoupled from both the memory section and the first buffering means;
• transmitting a second image data bus request signal from the second means for buffering to the means for arbitrating after the second preselected time period has elapsed;
• using the arbitrating means to determine which of the first and second buffering means can access the image data bus to transfer image data with the memory section when the first and second bus request signals are received concurrently at the arbitrating means.