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

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

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Page of GA34-0003-6, -7As Updated August 20,1976By TNL GN34-0340When a program check interruption occurs on one of <strong>the</strong> four priority interruptionlevels, <strong>the</strong> address of <strong>the</strong> instruction being executed when <strong>the</strong> program check was detectedis saved automatically in <strong>the</strong> first word of <strong>the</strong> appropriate level table. The program checkmay be due to an invalid instruction, or an invalid address generated by an instruction. Ifan invalid instruction is detected, <strong>the</strong> first word of <strong>the</strong> appropriate level table (OIA) contains<strong>the</strong> instruction address. If an invalid address is detected, <strong>the</strong> OIA normally contains<strong>the</strong> address of <strong>the</strong> instruction that generated <strong>the</strong> invalid address. (There is one exception tothis. If a higher level priority interruption occurs during a branch to an invalid address, and<strong>the</strong> interrupt is accepted immediately following <strong>the</strong> branch instruction, <strong>the</strong>n <strong>the</strong> invalidaddress is not used or checked until control is returned to <strong>the</strong> lower priority level. Under<strong>the</strong>se circumstances, <strong>the</strong> OIA contains <strong>the</strong> address of <strong>the</strong> PLEX instruction that releasedcontrol from <strong>the</strong> higher priority level.) The contents of storage location 9, which contains<strong>the</strong> starting addreE of <strong>the</strong> program check servicing routine, are <strong>the</strong>n automatically loadedinto <strong>the</strong> IAR and <strong>the</strong> servicing routine is given control. (Refer to "Reserved Storage Locations"in this chapter.)Power/Thermal WarningA power/<strong>the</strong>rmal warning interruption occurs when <strong>the</strong> system senses a condition caused byvoltage or temperature changes that border on <strong>the</strong> operating limits of <strong>the</strong> system. (Referto "Power Failure and Thermal Warning" in Chapter 1.) Power/<strong>the</strong>rmal warning classinterruptions are controlled by <strong>the</strong> summary mask. If <strong>the</strong> summary mask is on, <strong>the</strong> classinterruption is inhibited.Power/<strong>the</strong>rmal warning interruptions are also affected by <strong>the</strong> settings of <strong>the</strong> consoleswitches as shown in Figure 3-5.When a voltage or temperature condition causes a power/<strong>the</strong>rmal warning interruption,<strong>the</strong> IAR contents (address of <strong>the</strong> next instruction in <strong>the</strong> interrupted program) are savedautomatically in storage location hex C. The contents of storage location hex A, whichcontains <strong>the</strong> starting address of <strong>the</strong> power/<strong>the</strong>rmal warning servicing routine, are <strong>the</strong>nautomatically loaded into <strong>the</strong> IAR and <strong>the</strong> servicing routine is given control. (Refer to"Reserved Storage Locations" in this chapter.)<strong>System</strong>/7 Interruptions 3-11

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