HP 3562A, Service Manual

Page: 556 / 570

S E RV I C E
MOD E L 3562A
8-1 06
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 FFT diagnostic tests run when the instrument power is tu rned
ON, during S E L F TE ST, or d u ring T E ST ALL. Display the FFT-diagnostic test menu using
the fol lowing sequence of keystrokes:
PRESET
RESET
SPCl FCTN
S E RV I C TEST TEST PROC
The menu now contains the fol lowing entries of FFT diagnostics tests:
FFT FU NCTN
FFT STATUS
FFT I NTRPT
FFT RAM
FFT ROM
FFT C L I NTFC
Details of each test fol lows:
FFT FUNCTION TEST
TEST FFT
This test performs a l l the tests fou nd in the rest of the menu (status, interrupt, RAM, ROM,
and global interface tests). It also exercises the FFT functions by perform ing a forward
and a reverse FFT, and Hanni ng, u n iform, flattop, and user-defined windows on a known
block of data. The resu lting checksum is com pared to a known value by the C PU.
If the FFT function test fails but the analyzer appears to work correctly when analyz ing
a fixed sine signal and all the rest of the diagnostic tests for this board pass, investigate
the pseudorandom number generation block. I t is reset prior to doing the math for the
special functions of this test so that the resu ltant checksum is repeatable. If the PRN
generator is not reset or does not operate correctly, the checksum generated won't always
agree with the stored checksum.
The FFT function test is the most extensive diagnostic test available to test the FFT board.
It is executed as a su bset of the tests performed whenever the S E L F TEST and TEST ALL
tests are ru n.
FFT STATUS TEST
This test qu ickly checks the operation of the system bus operation between the CPU and
the FFT boards. The CPU add resses the FFT board and loads a command to it which causes
the FFT microprocessor to return the CPU command data. This tests the system interface
circu its (in both di rections), the internal data bus, the FFT microprocessor system, the
transceiver between the TMS320 m icroprocessor and the internal data bus, and both inter­
rupt circu its. If this test passes you know that the CPU can talk to the FFT microprocessor
and the FFT m icroprocessor can interpret commands and respond (talk) to the system CPU.