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Model 8901B
Service
P I 0 A13 CONTROLLER ASSEMBLY
--1
-----
r
I
I
I
1
7
TO OTHER SECTIONS
,
SELECTBUFFERS
PI0 A3 AUOlO
OE.EMPWASIS
A N 0 OUTPUT ASSEMULY
--1
- -
I---
I
I
INSTRUMENT BUS
P I O U 9 CPU
ENABLEOECODER
I
I
SELECT DECODER
I
P I
ILI
&
G
TO RF & AUDIO SECTIONS
!
TO
AUOlO SECTION
I
I10 10
'
r31H1
" .
G
OG.
lG,
F O I L 1
P I I L I
ull
26
TO
AUOIOSECTION
I
z
e-2'LI
OEMUX
3 G '
TO OIGITAL SECTION
c*3'L'
r 4 ILI
TO
REMOTE INTERFACE
11011
'
. l
'
110 12
5G
'
1 1 0 13
' G
I
TOKEYBOARO
AND DISPLAY
'
c J I H 1
. 2
; ;
r=7ILl
'
/
SO
IHI
I
A
I1
IHI
1/001
'
/
SO
IHI
I
I1
IHI
1/001
I
$2 /HI
$3
IHI
i
I
I10 02
1\
rZ'L)
*.
'
s 3 ' 0
110
03
$2 /HI
I
$3
IHI
i
I
I10 02
1\
rZIL)
110
03
'
s 3 ' 0
I
l . J
$=
I
-i4
I
u
I
I
I-4
ILI
I
I
HIGWPASS
FILTER CONTROL
R E G
OATA BUFFERS
I
I
NO HPF
ILI
50
HZ
HPF
ILI
300
HZ
HPF (L)
0.E PRE-OISPON ILI
I
0-E PRE.OISPOFF ILI
Figure
80-7.
Example Showing Instrument Bus Hookup
Instrument Bus
Figure 8D-7 shows a typical hookup on the Instrument Bus. The Instrument Bus lines are broken
down into three groups: enable (e), select
(s),
and data (d). The enable code
(e0
to e3) comes from 1/0
lines 10 through 13 of the
CPU
(A13U9).
Three of the enable lines (eo, e l , and e2) are decoded by the Enable Decoder (A13Ull) to activate one of
eight unique enable lines (e=O to e=7). The fourth line (e3) enables the decoder itself. The enable lines
run to various instrument sections. Typically, each line is dedicated to a specific section or operational
function; for example, enable line e=l controls audio-related functions in the Audio Section.
The select
(SO
to s3) and data (do to d3) lines come from 1/0 ports 00 to 07. The eight lines run in
parallel to all sections of the instrument where they are decoded on the assemblies. (In the RF Section
Service Sheet BD5
m - 4 9
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