Service Model 8901B
hexadecimal value
for
d.
Exceptions
to
this are Special F’unctions
0.5sd
and
0.6sd,
which control the
display itself.
The hexadecimal characters
A,
B, C, D,
E,
and
F
are displayed on entry
as
A, b, C, d,
E,
and F, and
they are entered from the keyboard
as
Shift
0,
Shift 1, Shift 2, etc.,
or
from the HP-IB
as
XO, X1, X2,
etc. Table 8B-1 summarizes the hexadecimal entry and readback for Direct Control Special Functions.
Table
8B-1.
Hexadecimal Information for Direct Control Special finctions
Hexadecimal
Character
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
Decimal
Equivalent
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Binary
Equivalent
0000
0001
001
0
001 1
01
00
01 01
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Keystroke
Entw
0
1
2
3
4
5
6
7
8
9
S
(Shift)
0
S
(Shift)
1
S
(Shift)
2
S
(Shift)
3
S
(Shift)
4
S
(Shift)
5
HP-IB Code
Entry
0
1
2
3
4
5
6
7
8
9
xo
x1
x2
x3
x4
x5
Display
On Entry
0
1
2
3
4
5
6
7
8
9
A
b
C
d
E
F
Direct Control Special Function Applications.
Direct Control Special Functions are most often used
to provide manual control
of
various switches
or
digital-to-analog devices in the hardware. The following
examples illustrate how to use Direct Control Special Functions:
Example
1
In the path of the demodulated audio signal
is
a set
of
selectable, active high-pass filters which
are
located on the A3 Audio De-emphasis and Output Assembly.
A
simplified diagram
of
the filters
is
shown
in
Figure 8B-1. The filters and through path are selected by analog switches U12A, U12B,
and U12C. Table 8B-2, which is associated with the troubleshooting
of
the filters, lists the Direct
Control Special Functions normally used to control the switches.
Table
8B-2.
Audio High-Pass Filter and
FM
Pre-Display De-Emphasis
Direct Control Special &netions
Direct Control Special Function
Pre-Display On Pre-Display
off
Check
Thru Path
0.141 0.149
50
Hz
HPF 0.142 0.14A
300
Hz
HPF
0.1
4c
To insert the
50
Hz
High-Pass Filter, key in 0.142 SPCL or -142 SPCL. The display will show
00001C.0010, indicating that the Controller received
d
=2
from
the keyboard (or HP-IB), issued
it
to the Instrument
Bus,
and read
it
back.
If
the circuitry on the assembly
is
working properly,
switch U12A will close and the audio signal will pass through the
50
Hz High-Pass Filter.
8B-2
Special
Functions
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