| 摘要 |
PURPOSE:To detect an external bus error easily in real time by an extremely simple circuit by adding a circuit which compares the data delivered to an external bus with the data supplied from said bus in a data output mode. CONSTITUTION:An external bus error detecting part 1-0 consists of an output buffer 2, input buffer 3 and a comparator 4. The comparator 4 receives supply of a signal d0 and an output signal of the same logical value as a signal D0 sent from the buffer 3. The logic values of these signals are compared with each other, and a comparison result signal P0 of the logical value ''1'' is delivered when no coincidence is obtained from said comparison. The signal D0 has the same logical value as the signal d0 when an external bus is normal. When the logical value of the signal D0 is different from that of the signal d0, it is known that an external bus error occurs. Then the signal P0 of the logical value ''1'' shows that the external bus error is detected. |
