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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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