HP 3562A, Service Manual

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MOD E L 3S62A SERV I C E
The D FA functional test performs a zoom measurement o n data created by the system
CPU and stored in gl obal RAM. The test simulates measuring a 1 6 kHz squ are wave with
a zoom window 1 0 kHz wide, centered at 1 6.5 kHz. The results are processed by the FFT
and FPP boards to create a power spectrum . The power spectrum is checked for proper
ampl itude of the fundamental and noise floor.
This test exercises a l l circu itry in the DFA except the trigger circu itry in the measurement
state machine block and the trigger LED control block on the A6 board. Prior to erform ing
this measu rement, the interru pts used to indicate the end of measurement are tested . If
either of the two interrupt tests fail, the zoom measurement is not performed. This rotects
against fai l u re of the program to ru n to completion. When the interrupts are inoperab le,
the DFA can not signal the CPU that the measurement is com plete and the program waits
indefinately.
If the D FA fu nction passes, the fol lowing messages are displayed :
DFA Filtered Chan I nterrupt
DFA U nfi ltered Chan I nterru pt
DFA Functional Test Passes
Passes
Passes
The fi ltered and unfi ltered interrupt tests refer to the types of interru pts used to perform
the measurement. Data is transferred from global RAM into the digital fi lter control ler,
where it may or may not be fi ltered, depending on the type of measu rement requ i red.
There is an interrupt indicati ng end of measurement for each of the the two cases.
If either of the interrupt tests fail, test the local bus (fi rst) and then the DMA bus with
the diagnostic tests of the same name. The descriptions of these tests appear later in this
section.
If the DFA functional test fai ls, begin troubleshooting by running the local bus test; it
has to fu nction correctly before anyth ing else can be tested.
If tile DFA fu nction test passes, the AS, A6 assem bl ies are probably functioning correctly
with two exceptions: neither the trigger circu itry in the measu rement state machine block
nor the circu itry in the trigger L E D control block on the A6 board are exercised by this test.
If the trigger is fai l ing and the prob lem has been isolated to the AS, A6 assembl ies, start
trou bleshooting the Trigger Control PAL (A6 U409) and the Start/Stop Contro l PAL
(A6 U309). Other possible problem areas incl ude the AM9S1 3 cou nter (A6 U1 09) and the
trigger interrupt flag (A6 U303).
If the 'TR I G G E R I NG' or 'MEAS U R I NG' L E Ds are not fu nctioning correctly, start
troubleshooting the Trigger L E D Control Subblock.
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