PURPOSE: To easily test the stack fault of a bus by providing plural common input/output(CIO) bus driver which is connected between a microprocessor and the respective buses to be a test object.
CONSTITUTION: A counter 14 which is reset by a reset signal 12 inputted from a microprocessor is provided with four-bit outputs BO-B3, a bus test data selecting signal 34 is generated by supplying the AND 16 outputs 18 of output bits BO-B3 and a select gate 38 gives a test data signal 40 to a CIO bus driver 32. The bus signal is detected by responding to the given test data signal 40, a CIO input 46 is supplied to an all-zero detection OR gate 48 and an all-one detection AND gate 50 and an error signal 62 is generated by responding to the detected bus signal which indicates a bus fault. Thus, error detection with high reliability is efficiently executed.
KENISU KURUUDO HINTSU
JIYATSUKU KURISU RANDORUFU
MAAKU ROOREN RUUDOKUISUTO
TOOMASU MIRUTON UOOKAA
| JPH01135559U | 1989-09-18 |