| 摘要 |
PURPOSE:To detect an abnormality of an operation in its early state by execut ing vector development to the inside of an area from the outside of an image memory area by prescribed data, and comparing a point which crosses a bound ary point at that time, with an intersection which has been set in advance. CONSTITUTION:When a command for instructing a function check of a graphic drawing circuit 6 and check pattern data are sent from a CPU1, the graphic drawing circuit 6 executes an operation by a drawing start address and a drawing end address, and executes vector development between both the addresses. Comparing circuits 13, 14 compare an output of the graphic drawing circuit 6 and an output a registers 11, 12. The outputs of the comparing circuits 11, 12 are provided to an AND circuit 21 through AND circuits 17, 18 and an AND circuit 20, and an error signal for displaying a fact that an error exists in the operation of the graphic drawing circuit 6 is outputted.
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