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

Read ISWEX0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA00001 XXX 0 10000001011 *** ** *XXXXXXi 111 i i II 1111 Ill 1 I 111 11111•••,;■11.,...............■■ •••■■•■••,..■■•••■■••„,••••••••■••••,,,•■••••■•••••,,•■• ••••••■•■•• ,...N.0.."...0 8-F 4 0 B 0 0-3 XThis command stores the interrupt status word extension (ISWEX) from the disk storagemodule into the index register (R), or the accumulator if R=000. No interruption resultsfrom execution of this command.Bits 5 through 15 can represent one of two sets of conditions in the disk file drive whenread by the read ISWEX command. A plug connection is made to the normal or diagnosticposition inside the disk storage module to determine which set of conditions is read.The read ISWEX command is used in conjunction with the write diagnostic control command,described previously, when the status bits are connected to the diagnostic position.Interrupt Status Word Extension (ISWEX): Bits in the ISWEX are set by conditions thatoccur after a read or write command is completed, but while the disk storage module isstill busy. Setting any one of bits 0 through 4 also sets bit 15 in the disk storage moduleISW.Some conditions that set ISWEX bits are dynamic conditions. That is, the indicator isturned on only for the duration of the condition. However, during execution of a readISWEX command, the indicators will not change even though the condition may changeduring the command execution. Significant bits in the ISWEX and their meanings are:Significant Bits Meaning0 File data unsafe. The disk storage module detected one of the followingunsafe conditions and made the file not ready:1. Write unsafea. Write was selected and no write transitions were detected.b. Write was selected and both heads were selected.c. Write was not selected and the write current source was turnedon.2. Erase unsafea. Write was selected and the erase current source was not turnedon:b. Write was not selected and the erase current source was turnedon.3. Read/write selection unsafea. Read was selected and either write or erase were selected.b. Access mechanism was moving when either write or erase wasselected.1 Missing address mark. The index mark was passed twice and aspecified address mark was not found. In this case, ISW bit 5(no record found) will also be set. If the next sequential ID readfrom the disk does not compare with the expected ID during amultisector cycle steal operation, missing address mark is set.2 Equipment check. The disk storage module has detected a failure withinthe module. Additional information will normally be contained in bits5 to 15 of this status word.IBM 5022 Disk Storage Module 15-23