LEVEL 1 DIAGNOSTICS ERROR RETURNSRepair Procedure 02The RAM PATTERN TEST writes data patterns into memoryand then reads the patterns back to verify that allthe data bits in memory are functioning properly.This test will detect the presence of stuck data bitsin a RAM or an intermittent bus driver. Comparing theexpected data with the observed data will show thedefective bit positions. If the segment addresschanges randomly with repeated execution of the RAMPATTERN TEST, then the problem is also associatedwith the addressing hardware and the RAM ADDRESS TESTshould be used to provide further information. Apattern failure that reports a constant segmentaddress can be checked using Repair Procedure.Intermittent failures that are reported as notDuplicated will require re-use of the RAM PATTERNTEST to determine if there is an actual problem.Intermittent failures reported as Duplicated couldbe the result of the RAM IC or the data bus to theRAM IC. Figures 5-13 and 5-14, respectively, show thelocation of RAM memory hardware on the Main ProcessorBoard.5-18
