| 摘要 |
PURPOSE:To use an external storage device from a substitute bus without using an instruction word by turning off a logical connection control system of a control device and the external storage device, in case a fault which makes normal operation of a microprogram impossible is generated. CONSTITUTION:A system is constituted of magnetic tape devices NTU33, 34, and magnetic tape control devices NTC1, NTC2, a control signal from a channel is received by connection controlling circuit 1, 11 of each NTC, and by a program of storing circuits 3, 13, a data is transmitted and received through data controlling circuits 2, 12. Also, various faults are detected by fault detecting circuits 4, 14, and the latch of a logical connecting state of the NTCs 1, 2 and the NTUs 33, 34 is controlled by switching controlling circuits 8, 18. In such a state, in case a fault which makes a normal operation of a program impossible is generated, the latch of the logical connecting state of the NTC1, the NTC2 and the NTUs 33, 34 is turned off, the faulty bus is switched to a substitute bus without using an instruction word, and the storing circuit 13 or 3 is made available. |
