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

This command places the disk storage drive, specifiedby the area code, in CE mode if modifier bit 15is on, or removes the disk storage drive from CEmode if modifier bit 15 is off.Initialize WriteData Table Address (TA)15 0 4 15Control: A–Models,1Aloo,: emeCI ofInder1 . . ISpecifies the diskstorage drive15 0 4 6 13 151 . 0 . 00 = Seek forward1 = Seek backward•Word Count (n)DataData..-9;pecifies the diskTA storage driveTA+1TA+2Data JTA+nSpecifies sectorto be written117887 I117885AThis command causes the carriage to move (seek)the number of cylinders specified by bits 7 through 15of the IOCC address word. The number of cylindersspecified may be from 1 through 202.Modifier bit 13 specifies the direction of theseek. If modifier bit 13 is on, the carriage movesbackward (toward the outer edge of the disk). Ifmodifier bit 13 is off, the carriage moves forward(toward the center of the disk). At the end of theseek operation, an operation complete interrupt isgiven.If two seek operations are given without a 22. 5-ms delay between them, an error may occur on thenext read/write operation.This command causes data in a table starting at thecore storage location specified by the IOCC addressword to be written in the sector indicated by modifierbits 13 through 15. The first word of the table containsthe word count (n), which defines the number ofdata words to be written. Up to 321 words (one corn-.plete sector) may be specified. A separate commandmust be given for each sector or portion of a sectorto be written.The word count and data words are transferredby means of data channel (cycle steal) operations.When the number of data words specified has beenwritten, an operation complete interrupt is given.This command is treated as a no-op if given while thedisk storage drive is busy or not ready.Control: B–Models15 0 4 5 15Cyl ,inger Address 1 11 ,0 0Specifies the diskstorage drive117886 IThis command causes the carriage to move (seek) tothe cylinder address specified by the IOCC addressword. An operation complete interrupt is given whenthe seek operation is completed. The cylinderaddress may range from 0 through 202. A cylinderaddress greater than 202 will cause a seek error andan operation complete interrupt.WRITE CHECKING: To achieve the maximum levelof performance, the program should provide forrepetition of XIO initialize writes that indicate anydata transfer errors. These errors are often due totemporary conditions that are not present in subsequentretries.An XIO initialize write that does not write correctly,because of temporary or intermittent conditions,can be detected immediately by performing aread check operation. Thus, "soft" write errors canbe corrected while the data is still available.In IBM programming systems, use of read checkis optional. The programmer should weigh the timeconsumed by error recovery procedures against thetime consumed in read checking.166