NCR PC4i Service Manual

Also see for PC4I: Technical reference Service manual Owner's manual

Contents

NCR PC4i Service Manual Manual pdf 124 page image

LEVEL 1 DIAGNOSTICS ERROR RETURNSERROR CODESThis section describes the error reports from theNCR Personal Computer SERVICE DIAGNOSTICS program.The reports from the diagnostics are in coded form.This reduces the large overhead of program coderequired for text. Codes are exemplified in theaccompanying text.RELATIONSHIP BETWEEN MAJOR CODES, DETAILCODES AND REPAIR PROCEDURESError codes are broken down into MAJOR and DETAILcodes. In addition, ADDR(ess), EXP(ected) DATA, andOBS(erved) DATA information is also displayed whereappropriate. The MAJOR codes are, in general, adescription of the type of test being performed whenan error was encountered. This code is a BCD valuethat is displayed on the CRT and also presented tothe printer data port. Each MAJOR code may haveseveral DETAIL codes associated with it. The DETAILcodes are specific descriptions of the error and aredisplayed as hex values on the CRT only. Data that isto be returned from a particular register or memorydevice is displayed in the EXP DATA and OBS DATAfields. If the OBS(erved) DATA does not match theEXP(ected) DATA then an error has been detected. TheADDR(ess) field is for memory related failures.After every MAJOR CODE the "Repair Procedure" that isrecommended to troubleshoot the faulty condition ispresented. Additional "Repair Procedures" may followspecific DEVICE codes. On the Main Processor Board(MPB), each semiconductor component is identified bya "U" number. The repair proc e d u r e s spec i f ycomponents on the MPB by the appropriate "U" number.Figure 5-6 shows the location of components on theMPB by "U" numbers. Equipment recommended forperforming repairs includes: Multimeter, DigitalLogic Probe.5-8