IBM System/7 Functional Characteristics - All about the IBM 1130 ...

Read ISW0 5 8 11 16 20 26 31Op code0 0 0 0 11 1 1 1RXXXI iFun0 1 011Zeros0 0 0 0 01111Mod0 0 1 1IIIDAMA• * * * * *XXXXXX11111 111110 8-F 4 0 3 0 0-3 XThis command stores the disk storage module ISW into the index register (R), or theaccumulator if R=000.Interrupt Status Word (ISW): Bits in the ISW are set by conditions that occur after aread, write, or seek command is completed, but while the disk storage module is still busy.Since these errors cannot be indicated to the program by the condition code, interruptionsresult from setting on any ISW bit except bit 12, the busy bit. After the interruption isaccepted, executing any command addressed to this module (except read DSW or readISWEX) resets the ISW.Descriptions of significant bits in the disk storage module ISW and their meanings follow.An asterisk (*) next to the bit number indicates that the summary status indicator is alsoset when the resulting interruption request is presented to the processor.Significant Bits Meaning0* Attention. One of the following conditions has occurred:1. The disk storage module was prepared for interruption requestsand the disk file drive became ready after a file start sequence.2. The disk file drive was ready and the disk storage module has justbeen prepared for interruption requests.2* Overrun. One of the following conditions has occurred:1. DPC file—A data service interruption request was not servicedwithin 40 microseconds. The any-error bit (bit 3) and the device-endbit (bit 13) are also set in the interrupt status word by this errorcondition.2. CS file—The channel has failed to respond in time to a requestfor service from the module. Overrun is an exception not an errorcondition; however, an overrun condition will result in the operationbeing terminated and an interruption being presented. Any-error bit(bit 3), channel-end bit (bit 11), and device-end bit (bit 13) will beon in the ISW.3* Any error. One or more of the ISW error bits 2, 4 through 7, and/orbit 15 are set on.4* Drive became not ready. A disk file operation was in progress and thedrive became not ready due to a failure in the disk storage module.Additional information can be obtained by reading the ISWEX. Theany-error bit (bit 3) and the device-end bit (bit 13) are also set inthe interrupt status word by this error condition.IBM 5022 Disk Storage Module 15-21