CONTROL SYSTEM FOR INPUT AND OUTPUT INSTRUCTION

摘要

PURPOSE:To prevent deterioration of efficiency of a fast central processor by sending CC=2 back to the next input/output instruction even at a time point when the connection is not confirmed yet with an input/output device on an I/O interface on the same channel by the input/output instruction delivered precedently. CONSTITUTION:At the time of a central processing unit 10 delivers an input/ output start (SIOF) instruction to an input/output device 14 via a channel 13, the channel 13 starts an input/output action by an SIOF instruction that is delivered to an input/output device 15 via the channel 13 immediately before the SIOF instruction is delivered to the device 14. Thus it is displayed that a channel state register 23 is set under a channel communication mode as long as the SEL-OUT signal is equal to '1' even though the initial start sequence is presently carried out on an I/O interface and the OPL-IN signal is still kept at '0.' Thus a centralized control part 20 can give a report immediately to the unit 10 via a condition code setting signal 31. Then the unit 10 sets a condition code (=2) and can proceed to the next instruction processing.