| 摘要 |
PURPOSE:To attain a folding test including a circuit which switches the connection of a bus from a waiting host system by providing a register circuit for folding test and a control circuit for return test timing supplied from the waiting host system. CONSTITUTION:A return test timing control circuit 2 detects a folding test request 1b fed from a waiting host system through a matching circuit 201. While the gate to a switching circuit 31 is closed temporarily with the gate to a switching circuit 32 opened with the timing produced specially after a matching circuit 202 confirms that no access is given to an input/output controller IOC4 from the host processor of an operation system. Here the access fed to the IOC4 from the the operation system is kept waiting. Thus no access is supplied to the IOC4 although the gate is opened to the circuit 32. Then the IO writing/reading are possible to a writing/reading register circuit REG1 for folding test. |
