Tektronix 494AP service manual O a

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Microcomputer System Test

.The microcomputersystemtest is chosenby setting switch #8 ctosedand switch #7 ogenin S1O6O.fni displayis inoperativewhilethis test is beingperformed. The microcomputerreports th€ t€st resultsvia the LEDS on the GplB board ratherthan on the GRT. lf a prob- lem is encountered,the test stops and the problemis indicat€d by one of the LEDSon itre GptB Ooard. tf no problemis found,the systemtesttakestwo minutes.

,The system test _doesnot begin normal operation afterthe test is complete.

.. . A.ddrelsgsare specifiedas hexadecimalnumbersin this description.

l. The microcomputerfirst veriftesthe check sum of the systemROM portion of U30S0on the Memory board. The checksum test usesno memoryexceptfor U3050. The correct ROM must be instailed,the clock on the Processor board must be present, and the microcomputersystembus mustbe operatingcorrectty.

tf the conect check sum is not obtained,the routine haltsand lights DS1047on the GplB board. lf the test stops but does not tight DS1O47,and everythingetse seemsto be in order,the AddressBus Test (desiribeo laterin this section)shouldbe performed.

2.Tl'rgmicroeomputernext checks part of the pro_ cessorinterfaceto the instrumentUus'pln,U1010,on the Processorboard. lf the test fails,the routinestops and lights DS1050 on th€ GptB board. tf the test succeeds,the processorassumesthat the instrument bus interfaceis working, and displays PROCESSOR SYSTEMTEST,PLEASEWAT.on the trt.

3.The microcomputernext checksRAM. The RAM test containsthree parts. The first part performsa quick test of all non-batterybacked-upRAM (U10.10and U3020 on th€ Memory Board). The microcomputer loads the bit paftern 01010101into a RAM tocation, reads the location,and compareswhat is returnedto what was stored. The microcomputerthen repeatsthis test with the pattern10101010.This step does not rely on the RAMbeinggoodto execute.

. lf a readingerror occurs,the microcomputerstops the test and pulsesLEDDSlO4gon the GplB boardtire numberof times correspondingto the RAM that failed the test (referto Table6-11).

The secondpart of the test is a MovingInversions

test of all RAM (volatile and non-volatile)This. test assumesthat a few byes of the RAM are good. lf a RAM faits this test, DS1O4gon the Memory board is pulsedas describedearlier.

Maintenance- 4g4Ll4g4ApServiceVot.1

Tabfe 6-11

u 1 0 1 0 u3020 ul030

The third part of the test is similar to the first part. However,the memorycontentsare allowedto residein memoryfor thirty secondsbefore beingread back. The resultsare reportedvia DS104g.

4.The microcomputernext performsa check sum test of all ROMs.The checksum storedin eachROMis comparedto the checksum formed by the successive 16-bitspirat sum of each byte in tne nOU, startingat the third location in the ROM. The ROMnumberco-dedinto each ROMwill causean error if a ROMis installed in the wrong location.

The Tektronix part number is also coded into each ROM. lf the part numbersuffix and its complement, which are stored in th€ fifth and sixth bytes of the ROM header, do not read as complements,the microcom- puter assumesthat no ROM is installedand does not attemptthe checksumtest.

lf a bad or misplacedROM is found,the microcom_ puter pulses DS1049on the GplB board N+1 times, whereN is the numberof the ROM in error(e,g.,a bad ROM #3 will cause four pulses; refer to TableGi2). MissingROMsare reportedas describedin part6.

Table6-12

TEST

ROM ROM	DSl049
Saakct	Board

0u3060 A54Memory 1

1u3060 A54Memory 2

2u 1 0 1 0 456GPIB 3

3u 1 0 1 0 456GPIB 4

4u1020 A56GPIB 5

5u1020 A56GPIB 6

6ul025 A56GPIB 7

7	u1025	456 GPIB	I
I	ul035	456 GPIB	9
9	ul035	A56GPIB	1 0
1 0	u3015	456 GPIB	1 1
1 1	u3015	456 GPIB	1 2
1 2	u3020	A56GPIB	1 3
1 3	u3020	A56 GPIB	1 4
1 4	u3030	456 GPIB	1 5
1 5	u3030	456 GPIB	1 6
1 6	u3050	A54 Memory	1 7
1 7	u30s0	A54 Memory

6-51

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