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10
10
.
5
.
Test
2 Switch decoding
test
Due
to the capacitors
in
the
circuit
which
read-out the function switch, the
sig
natu-
res
on
point
3
of
D1916
and
D1919
|(P24|
).
are unstable.
Therefor
e
the
microcomputer
reads the signatures
on
|P24l
and
sends
them
to
lP25.l
This
gives a stable
signature
which
can be
measured by
the
signature analyser.
Settings signature analyser
SWITCH DECODING
Setting
Edge
Testpoint
Signalname
start
Ti
(neg)
TPM
P17
(D1904pin34)
stop
(pos)
TPM
P17
(D1904pin34)
clock
(pos)
TP15
ALE
(D1911
pin 11)
ground
—
TP1
Logic
0
NOTE:
1.
The
testrom
placed
in
the
D
1909
socket.
(Both
ROMs
removed).
2:
Short
circuit
TP10 and TP1
1.
3.
Reading on
display
£
S
4.
Reference
logic
0
=
0000
logic
1
=
C66C
POSITION
i
SIGNATURE
Vr=
-1
3AU8
1
7FUF
Hz
45AU
TRIGGER LEVEL
!
8876
S
!
968A
'c
1
251C
-w-
1
139P
0
1
ASK
A<v.
I
5AU2
A=:
!
677C
Vz= AND"*/-
.
1
HUH
Vr= AND
AUTO/mAn!
538F
V=:
AND
DOWN
1
3AF7
V=
AND UP
1
IC2P
Vzr.
AND
ABUS
(LEAD
IN
ABUS}
j
7520
LOGIC 0
=
0000
LOGIC
1
=
C66C
r
\
"
?"•
L
f'
li
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