| 摘要 |
PURPOSE:To decide a fault of an address bus line, by writing different information in a certain address, and an address whose contents variation of 1 bit becomes equal to said address, and comparing a read-out data and a write data by said certain address. CONSTITUTION:To an address 0 of 3 bits, etc. of an RAM, and addresses 1, 2 and 4 whose contents variation of 1 bit becomes equal to 0, data 1111, 0000, etc. are written respectively. Subsequently, when reading out the address 0, if the second bit, etc. of the address line are opened, an address 3 is designated substantially, and a read-out data becomes 0000. Accordingly, each bit contents of a register Reg 2 is which a write data 1111 is stored and those of a register Reg 1 in which the read-out data 0000 has been stored are compared by an exclusive OR circuit EX, and if conetents of the register Reg 2 have a fault in one of the address bit buses, information 0000 is stored. When the address is grounded, it is executed in the same way, and an address concurrence caused by a fault of an address bus is also decided. |
