| 摘要 |
PURPOSE:To initialize a memory without hindrance, by providing a diagnostic mode and normal mode. CONSTITUTION:Under normal operations, 2-byte write data A are inputted in a data selecting section 22. When the write data A are inputted, the 4-byte data of a main storage device 1 are written in the main storage device 1 together with the lower 2 bytes of a read data buffer 23 read out from the main storage device 1. 4-byte data, which are completed when a next write data B sent from a CPU 3 are combined with the lower 2 bytes, are inputted in an error detecting/correcting section 21 through the read data buffer 23 and error detection/correction is performed on the 4-byte data. According to the error detection/correction, an ECC code implementing/correcting section 24 implements an ECC code and writes the ECC code in the main storage device 1, and thus, the data are completed. When the CPU 3 designates a diagnostic mode, an ECC code selecting section 25 selects a register 26 for diagnosing ECC code and a diagnosing ECC code is used for the writing process.
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