| 摘要 |
PROBLEM TO BE SOLVED: To fast fetch an instruction even in a low speed program ROM by reducing the number of real accessing times. SOLUTION: This device consists of a program ROM 37, a memory controller 36 and a CPU 30 of a fixed instruction length, preliminarily analyzes a program code, generates conversion table 38 between compression code and program code from an appearance frequency, replaces n pieces (256) of upper program codes with the compression code of the number of bits which is less than actual instruction length in the order of a high appearance frequency, compresses it in the unit of burst transfer, stores it in the ROM 37 from a burst start address in a burst unit, makes the controller 36 extend the compression code into the program code based on tables 38 and 33 when it is read and supplies it to the CPU 30. The conversion table is provided on the ROM 37 and is written to RAMs 32 and 33 when initialization is performed. Each conversion table is allocated to each area of the program.
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