| 摘要 |
PURPOSE:To detect easily a fault of a block address decoder incorporated in a memory board during its test by adding a block address to be supplied to the block address decoder to part of test data when writing the test data in a memory. CONSTITUTION:In an initial write cycle, addresses of blocks A-D of the memory board are (000), (001), (010), and (011). When the block address (000) is applied to the memory board 3, the block A is selected to write test write data in its memory chip. In a read cycle, the host three digit bits are replaced for the block address (000) by a data selector 5. Therefore, when normal write data including the block address of the block A is read out of the memory board 3, a comparator 6 generates a coincidence output. If, however, the decoder malfunctions to select a wrong block, the block address in read data is different from the address (000) of the block A and the comparator 6 geneates a dissidence signal indicating an error. |
