Systems Reference Library - All about the IBM 1130 Computing ...

Page of GA26-5918-8Revised July 14, 1971By TNL: GN26-02691. An XIO initialize read causes a command rejectinterrupt if given before the adapter has completedexecution of a previous XIO from the1800. The DSW will indicate command rejectand 1800 command stored; 360 command storedwill also be on if data transfer is in progress.2 An XIO initialize read causes a command rejectinterrupt if given after the adapter has previouslyaccepted any System/360 command, other thanwrite. The DSW will indicate command rejectand 360 command stored.Initialize Write (1800)The primary function of an XIO initialize write istransmission of data from the 1800 to the System/060. XIO initialize write is the complementary commandto a System/360 read command. The adapterresponse to an XIO initialize write depends on thestatus of the adapter according to the followingrules.IDLE ADAPTER: An idle adapter accepts an XIOinitialize write by saving the control word (area,function, and modifier), loading the adapter wordcount, and generating attention status to notify theSystem/360 of the pending operation. The adapterthen waits until it receives the complementarySystem/360 command (read).WAITING SYSTEM/360 READ: An adapter holding apreviously accepted System/360 read commandaccepts an XIO initialize write by initiating datatransfer, thus satisfying both commands. The datatransfer operation continues until either of twoevents occurs: (1) the System/360 byte count forthe read or 1800 word count for the XIO initializewrite is decreased to 0, or (2) an error condition isdetected. Termination of the operation is signaledto the 1800 by a transfer end interrupt. If the System/360terminated the data transfer, the haltindicator will also be on in the DSW. Terminationof the operation is signaled to the System/360 bychannel end and device end.BUSY ADAPTER: An XIO initialize write may berejected because of either of the following adapterbusy conditions:1. An XIO initialize write causes a command rejectinterrupt if given before the adapter has completedexecution of a previous XIO from the 1800.The DSW will indicate command reject and 1800command stored; 360 command stored will alsobe on if data transfer is in progress.2. An XIO initialize write causes a command rejectinterrupt if given after the adapter has previouslyaccepted any System/360 command, other thanread. The DSW will indicate command rejectand 360 command stored.Control (1800)XIO control is used to cause an unconditional reset ofthe adapter. This reset causes immediate terminationof adapter operations, and the adapter is notavailable to either system for the duration of thereset. If the System/360 is using the adapter whenan XIO control is given, an interface control checkmay occur in the System/360.If the 1800 system is reset by any means, theSystem/360 adapter goes off-Line. The STOP buttonin the System/360 must be pressed to establish aWAIT condition before the System/360 adapter canget back on-line.ADAPTER STATUSSystem/360 Status ByteThe System/360 adapter presents the followingstatus information to be included in the System/360status byte:Status ConditionStatus Byte Bit PositionAttention 0Busy 3Channel end 4Device end 5Definitions of the remaining status indicators in thestatus byte are given in IBM System/360 Principlesof Operation, Order No. GA22-6821. Figure 117summarizes the status information presented to theSystem/360 during initial selection.ATTENTION: Attention being on indicates that theadapter has accepted an XIO initialize read or XIOinitialize write, but has not yet received the requiredcomplementary command from the System/360.BUSY: Busy being on indicates that the adapter hasbeen selected by the System/360 and that one of thefollowing is also true: (1) an operation is pending,(2) a transfer is in progress, or (3) ending statushas not yet been accepted by the System/360. Busyis off when the adapter is idle.CHANNEL END: The adapter presents channel endto the System/360 during initial selection for controland no-operation commands, or with device end220