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

Control information contained in the R-register is used to identify a sector and has thefollowing format for the read initialize, read-sector-ID, read verify, and write initializecommands.0 2 1011 15F C T S1The F-bits (bits 0 and 1) are flag bits that indicate the condition of the disk track. Bit0=1 indicates a defective track; bit 1 = 1 indicates an alternate track.The C-bits (bits 2 through 9) contain the cylinder number.The T-bit (bit 10) is an extension of the sector number, indicating a sector located ineither an upper or lower track. T=0 indicates an upper track; T=1 indicates a lower track.The S-bits (bits 11 to 15) contain the sector number to be used in the specified track.Note: The read/write head (upper or lower) to be used must be selected by a prior seekcommand or load-next-sector-ID command.Seek0 5 8 11 16 20 26 31Op code R Fun Zeros Mod DA MA00001 XX OO100000 0011 ******XXXXXXiill ti 11 1111 111 11111 111110 8-F 2 0 3 0 0-3 XThe read/write heads of the disk drive move the number of cylinders and in the directionspecified by the control information word contained in the index register (R), or theaccumulator if R=000. The control information word has the following format:0 1 2 3 8 15NumberR H Dof cylinders• * * * * XXXXXXXXI I I I 1111111S•111.,,,■‘...../..,,OME./...■•••••,,•■•••••••••11.‘,■/X 0 X XFor models 1 and 2 of the disk storage module, the R-bit selects the disk (upper or lower)for use by a subsequent read or write command addressed to the module. R=0 selectsthe upper disk; R=1 selects the lower disk. For models 3 and 4, the R-bit always equals 1.The head bit (H) selects the read/write head to be subsequently used on the selecteddisk. H=0 selects the upper head; H=1 selects the lower head.The direction bit (D) specifies the direction in which the heads are to be moved. D=1specifies the forward direction (toward the center); D=0 specifies the reverse direction(away froth the center).Bits 8 to 15 specify the number of cylinders to be crossed.Upon completion of the seek operation, or if a seek error condition occurs, a deviceendinterruption request is presented to the processor module.Note: The disk and/or read/write head are selected for a subsequent read or write commandonly through the seek command or the load-next-sector-ID command.IBM 5022 Disk Storage Module 15-11