| 摘要 |
PURPOSE:To detect a program error reading data not subjected to initial set by applying set/reset of a check flag and memory write independently of memory read/write and resetting the check flag in the unit of address. CONSTITUTION:The address of a data area of a program is designated by a bus AB before program execution, a flag-on signal SET is given to the check flag memory 2 to set a corresponding address. When the data is set by the execution of the program an address and a memory write signal MR are outputted from a CPU, the data is written on the memory 1 and the flag of the corresponding address of the memory 2 is reset via an OR gate 3 at the same time. When the data of the address not set is read, since the signal MR is outputted while the output OUT of the memory 2 is set, generation of exception EXP is informed to the CPU via an AND gate 4.
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