| 摘要 |
PROBLEM TO BE SOLVED: To provide a byte read access method for selecting and reading a high-order byte or a low-order byte by a CPU for data written from the CPU of 16 bits not provided with byte read enable signal output to a controller. SOLUTION: At the read of the data of the controller 2 by read signals RD from the CPU 1, an interface circuit 4 provided with double address areas for mapping the controller 2 is provided between the CPU 1 and the controller 2, word access is performed by the address of one of the double address areas and byte access is performed by the address of the other one of the double address areas. Also, by the state of the 0 address of the address and an (n)-th optional address not used by the controller 1 among the addresses, byte enable signals BHE are prepared and the high-order byte or the low-order byte is selected and read.
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