Philips pm2521 - Page 182

10
10 . 5.
Test 2
Switch
decoding
test
Due to
the capacitors
in the circuit which
read-out the
function switch, the signatu-
res
on point
3 of D1916
and
D1919 |(P24|
).
are
unstable.
Therefore 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