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USE CONTROLS, DATA ENTRY, AND DATA DISPLAY
Mainframes

Fire Controlman Volume 03-Digital Data Systems
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Figure  8-27.—Example  portion  of  a  fault  isolation  table. or an NDRO that can be executed at any time by the technician or operator. The BIT is designed to test the computer hardware (CPU, IOCs, and any optional circuits)   and   return   pass/fail   results   to   the operator/technician.  Pass/fail  results  are  displayed  on the control, data entry, and data display man/machine interface. The BIT itself can consist of several levels of tests and subtests controlled from the computer’s front panel.  Some  internal  diagnostics  are  designed  to  test  all or selected sections of the computer. Errors can be displayed on the front panel using the data display man/machine   interface. The  computer’s  technical manuals or a ready reference index located on the front panel will enable you to decipher the error code. A fault isolation table (FIT) lists the error code and the location of  the  recommended  module(s)  that  will  correct  the problem. Figure 8-27 shows an example. On the pcb’s in some minicomputers, LEDs are also used to aid in fault isolation and identification. EXECUTE BOOTSTRAP. —Minicomputers are normally designed to boot or initially load the operating system program using a hardwired module (NDRO) located in the CPU. The NDRO is tailored at the factory and will select a particular peripheral device (disk, tape, and  so  forth)  based  on  the  position  of  the  bootstrap switch  located  on  the  computer’s  controlling  panel. Figure 8-26 shows a maintenance control panel with a bootstrap switch with two positions (1 or 2). The bootstrap  program  allows  a  more  comprehensive program to be loaded from the selected peripheral into main  memory  and  be  executed.  NDROs  are  also designed to perform a BIT, fault analysis program, or load a failure analysis program. To execute bootstrap, depress the run or load switch. INITIATE  OPERATIONAL  PROGRAMS.  — After the computer is booted, the operational program 8-22 is loaded, initialized, and started. The operational program is tailored to meet the command’s operational requirements or application. EXECUTE   AUTO   RESTART   OPERA- TIONS. —Auto restart operations are used when power is restored after a power loss. EXECUTE DIAGNOSTICS. —Execution of external diagnostics can be loaded into the computer and controlled using an external control device. They can also be loaded into the computer from a peripheral (disk  or  magnetic  tape  unit)  but  initiated  and  controlled by the computer. These diagnostics are very thorough and also offer the option of testing all or specific sections of a computer. They are more comprehensive than the BITs. Figure 8-28 shows the test results of an external diagnostic test as they amid be displayed on a controlling   monitor. Figure  8-28.—Examples  of  test  results  from  an  external






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