| 摘要 |
PURPOSE:To simplify the constitution of a memory control circuit and to reduce the area of a substrate and the manhour in packaging by switching a memory to a patch ROM only by writing the patch information of the patch ROM in a register without changing hardware. CONSTITUTION:The information of a space or the like requiring address replacement is obtained from a patch ROM control circuit 3 and written in the patch information register 2. Whether or not a decoding signal outputted from an address decoder 1 is replaced by the patch ROM is decided based upon the patch information. When the replacement by the patch ROM is available, a memory address is converted into a patch address by an address control circuit 5. Thus the switching from the memory to the patch ROM can be executed without changing the hardware, the constitution can be simplified and the manhour in packaging can be reduced.
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