Patent ID: 6119207
Filing Date: 2000-09-12
Classification: G06F,G09G

Abstract:
Apparatus for requesting data transfer from a memory to a display FIFO and between said memory and at least one other device n, and for issuing prioritized requests including low priority requests and high priority requests for data for loading into said display FIFO, comprising:a counter for tracking a FIFO data level of said FIFO;a comparator, responsive to said counter, for comparing said FIFO data level against a low priority threshold value;said comparator, responsive to said counter, for comparing said FIFO data level against a predetermined high priority threshold value lower than said low priority threshold value, said high priority threshold value representing a FIFO underrun threshold;said comparator activating said high priority request for data when said FIFO data level falls below or is equal to said high priority threshold value and deactivating an issued high priority request for data when said FIFO data level is greater than said high priority threshold value;said comparator activating said low priority request for data when said FIFO data level falls below or is equal to said high priority threshold value and deactivating an issued low priority request for data when said FIFO data level is greater than said low priority threshold value such that said low priority request is deactivated during a hysteresis time from the time said FIFO data level falls from said low priority threshold value to said high priority threshold value; anda low priority threshold value calculator for calculating said low priority threshold value such that said hysteresis time is substantially equal to a time S.sub.n required to service said at least one other device n from said memory.