HP 3562A Service Manual page 556

S E RV I C E
A. FFT Diagnostics
The diagnostic tests for the FFT board allow you to test groups of circu its to further isolate
a problem. A su bset of the F FT d i agnostic tests run when the instru m e nt power is tu rned
ON, d u r i n g S E L F T E ST, or d u ring T E ST ALL. D i s p l ay the FFT- d i agnostic test menu u s i ng
the fol lowing sequence of keystrokes:
PRESET
SPCl FCTN
The menu now contains the fol lowing entries of F FT d i agnostics tests:
FFT FU NCTN
F FT STATUS
F FT I NTRPT
F FT RAM
FFT ROM
F FT C L I N T FC
Deta i l s of each test fol lows:
F FT F U N C T I O N T E ST
This test performs a l l the tests fou nd in the rest of the menu (status, i nterrupt, RAM, ROM,
and gl obal i nterface tests). It also exerc ises the F FT functions by perform i n g a forward
and a reverse FFT, and Han n i ng, u n iform, flattop, and user-def ined w i n dows on a known
bl ock of data. The resu lting checksum is com pared to a know n va l u e by the C P U.
If the FFT f u n ction test fai l s but the ana lyzer appears to work correctly when analyz ing
a fixed sine signal and all the rest of the d iagnostic tests for this board pass, investigate
the pseudorandom n u m ber generation b lock. I t is reset prior to doing the math for the
spec ial functions of this test so that the resu ltant checksum is repeatable. If the PRN
generator is not reset or does not operate co rrectly, the checks u m generated won't always
agree with the stored checksu m .
The FFT function test is the most extens ive diagnostic test available to test the FFT board.
It is executed as a su bset of the tests performed whe never the S E L F T E ST and T E ST A L L
tests are r u n.
FFT STAT US T E ST
T h i s test qu ickly checks the operation of the system bus operation between the C P U and
the FFT boards. The CPU add resses the FFT board and loads a com mand to it which causes
the FFT m i c roprocessor to return the C P U command data. T h i s tests the system i nterface
c i rcu its ( i n both di rections), the i nternal data bus, the F FT m i croprocessor system, the
transceiver between the TMS320 m icroprocessor and the i nternal data bus, and both i nter­
rupt c i rcu its. I f this test passes you know that the C P U can ta lk to the FFT m i croprocessor
and the FFT m icrop rocessor can i nterpret commands and respond (ta lk) to the system C P U .
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R E S E T
S E RV I C T E ST T E ST PROC
MO D E L 3562A
T E ST FFT