HP 3562A, Service Manual

Page: 510 / 570

SERV I C E MOD E L 3562A
8-60
If this test fails and the local bus test passes, the fai l u re is probably in the Global Bus
DMA Control or Local Data/DMA Bus I nterface. The test message displayed on the screen
identifies which of the two should be investigated along with information describing wlhich
bit has fai led.
F I LTER BUS
The fi lter bus test should be used, after the operation of the local data bus is verified,
to test the transfer of data between the digital fi lter blocks and global RAM.
The fi lter bus test transfers one word from global RAM, through the d igital filter bus, into
the digital fi lter control ler IC, and then transfers it back to global RAM. Refer to the block
diagrams in Section VI to visu alize the data path. This seq uence is performed once for
each of the two channels. The test checks for either incorrect words or fai l u re to write
anything at a l l .
Failure to write anything, denoted by the message "DFA Chan
x
Write," i ndicates a problem
with measu rement control circu its on A6 or the d igital filter contro l IC correspond ing to
the channel that fai led (the meas u rement fai led to set up). Writing wrong data causes
the message "DFA Fi lter Bus
x"
to be displayed and ind icates a problem with the interface
IC associated with the fai l i ng channel.
If the fi lter bus test passes, the fol lowing circu its and processes are probably fu nction ing
correctly:
Paral lel I nput Control
G lobal Bus DMA Control
G l obal Data Bus I nterface
Address Output Registers
Unfi ltered channel output of the CHAN 1 and CHAN 2 Fi lter Controls
DFA PATT 1
NOTf
The message "DFA Filter Bus
1"
corresponds to the Chan 1 Digital
Filter Data Bus and "DFA Filter Bus 2" corresponds to the Chan 2
Digital Filter Data Bus.
The digital fi lter pattern test #1 is used for two pu rposes: with the loop mode off, it is
a diagnostic self-test of the digital fi lter blocks with no in puts; with the loop mode on,
it is a signatu re test for the d igital filter data busses and the global data bus interface
block. It is intended to be used as fol lows:
1 . Run the diagnostic (loop mode off).
2. If Transient Test #1 fails, perform the test with loop mode on and use the signatu res
to isolate problems in the output path (from the fi lter control ler IC through the global
data bus interface).