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

Significant Bits Meaning5* No record found. One of the following error conditions has occurred:1. None of the sector IDs on the selected track compared equallywith the sector ID specified by the command after at least one completerevolution of the disk.2. A specified sector ID was found, but the ID check character generateddid not compare equally with the check character read fromthe sector ID field on the disk.The any-error bit (bit 3) and the device-end bit (bit 13) are also setin the interrupt status word by this error condition.6* Incorrect length record. This error bit is set in a cycle steal operationwhen the subchannel detects a track index pulse and the word countis not 0. Bits 3, 11, and 13 are also set in the ISW.7* End of sector. The data field check character has been either reador written, thus signifying the end of the sector. This is not an errorcondition, so the any-error bit (bit 3) is not set along with this statusindicator bit. This indicator does, however, set the device-end bit(bit 13).Note: This indicator is not set during a format track operation.8* Storage data check. This error bit is set on during output cycle stealoperations only. It indicates that the storage location accessed duringthe current operation contains bad parity and, therefore, the contentsare not transferred to disk. The parity in main storage is notcorrected. Bits 3, 11, and 13 are also set on in the ISW.9* Program check. This error bit is set when the main storage addresspresented by the device for a cycle steal access is greater than thestorage configured on the system. Bits 3, 11, and 13 are also set onin the ISW.11 Channel end. This bit is set on as the result of termination of asubchannel busy condition. The condition lasts from after the startof a successful start I/O command to the point where the endcondition occurs, due either to a normal end condition or to anerror end condition. It is always accompanied by the device-end bitin the ISW.12 Device busy. The disk storage module is performing an operation.This is the only ISW bit that does not cause an interruption requestand is not reset by the read ISW command.13 Device end. The disk storage module has terminated the currentoperation. The termination may or may not be caused by a detectederror condition. This should be the only bit set in the ISW for anerror-free data-service interruption request during a read or writeoperation.14* Interface data check. A parity error was detected on a cycle stealinterface data transfer. Bits 3, 11, and 13 are also set on in the ISW.15* Read interrupt status word extension (ISWEX). A hardware failureor unsafe condition occurred in the disk file drive. The failure orunsafe condition can be further investigated by executing a readISWEX command addressed to the failing disk storage module.