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

Modifier bits perform the five functionsdescribed next.TAPE UNIT SELECT (Bit 10): This modifier bitselects the tape unit: 0 = tape unit 0, and 1 = tapeunit 1.DENSITY (Bits 11 and 12): These modifier bitsspecify the density as follows:00 = 800 bits per inch.01 = 200 bits per inch.10 = 556 bits per inch.FORMAT (Bit 13): This modifier bit specifies theformat for seven-track operation: 0 = unpackedformat, and 1 = packed format. This bit is ignoredfor nine-track operations.READ MODE (Bit 14): This modifier bit specifies thetype of read operation: 0 = normal read, and 1 =read while correcting. Read while correcting shouldalways be used unless error correction is to be eliminated.This modifier bit is ignored for seven-trackoperation. It is also ignored during the first time atape block is read (error not yet detected) for ninetrackoperation. See "Error Correction (Nine-Track)"for details.PARITY MODE (Bit 15): This modifier bit specifiesthe parity mode for seven-track operation: 0 = oddparity, and 1 = even parity. This bit is ignored fornine-track operations.Sense Devicellllllllllll •15 0 40 = Tape unit 01 = Tape unit 1This command may be used to:0 1 , 1.1.00 = Sense DSW1 = Sense word count1 = Program stop0 = No indicator reset1 = Indicator reset1. Place a tape unit in selected mode.2. Sense the tape unit device status word (DSW).3. Reset program resettable DSW indicators.815I15586C4. Sense the word count.5. Perform an operation stop to clear the datachannel.The modifier bits indicate the function, asdescribed next.TAPE UNIT SELECT (Bit 10): This modifier bitselects the tape unit: 0 = tape unit 0, and 1 = tapeunit 1.DSW Select (Bit 11): This modifier bit selects theword to be sensed: 0 = device status word, and 1 =channel word count.PROGRAM STOP (Bit 12): This modifier bit is usedto select program stop operation: 0 = no programstop operation, and 1 = program stop operation.RESET (Bit 15): This modifier bit controls the resetof the program resettable indicators in the devicestatus word: 0 = no indicator reset, and 1 = indicatorreset.The following paragraphs describe the variousfunctions that may be performed with an XIO sensedevice.TAPE UNIT SELECTION: Before a tape unit may beused, it must be placed in selected mode to preparethe unit for program operation. Tape unit 0 is automaticallyselected when P-C console RESET ispressed. Tape unit selection is changed by the XIOsense device.Once a unit is selected, it remains selected untilchanged by another XIO sense device.If an attempt is made to select a tape unit whilethe other is selected and busy, the busy tape unitremains selected. Bit position 1 of the DSW willshow that the selection remained unchanged.SENSE DSW: If modifier bit 11 is off, an attempt ismade to select the tape unit specified by modifier bit10, and the DSW of the selected tape unit is read intothe accumulator. The DSW is shown in Figure 91.Modifier bit 15 controls reset of the programresettable DSW indicators. If modifier bit 15 is on,the indicators are reset. If modifier bit 15 is off,the indicators are not reset.The indicators identified by DSW bits 12, 13,14, and 15 require a minimum of 5 pis from selectionof the tape unit before their status can be accuratelyplaced in the DSW. Therefore, if the status of theseindicators is desired, the XIO sense device that readsthe DSW must be given at least 5 pcs after the XIOsense device that selects the tape unit.174