Service Model 8903B
Keystroke
Entry
0
1
2
3
4
5
6
7
9
8
S
(Shift)
0
S
(Shift)
1
S
(Shift)
2
S
(Shift)
3
S
(Shift)
4
S
(Shift)
5
Table 8-1. Hexadecimal Information for Direct Control Special Functions
HP-IB Code
Entry
0
1
2
3
4
5
6
7
9
xo
x1
x2
x3
x4
x5
a
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
Display
On Entry
0
1
2
3
4
5
6
7
8
9
E
H
L
P
(blank)
-
Direct Control Special Function Applications.
Direct Control Special Functions are used in troubleshooting
to
provide manual control of various switches or digital-to-analog devices in the hardware where other special
functions
or
front-panel keys prove ineffective. Some examples will illustrate how to use Direct Control Special
Functions.
Example
1
In the measurement path of the input signal
is
a Programmable Gain Amplifier located on the A2 Input
Amplifier Assembly. A simplified diagram of the circuit
is
shown in Figure 8-4. Amplifier gain is selected
by analog switches U11(1), U11(2), U11(3), and Ull(4). Table
8-2
shows the Direct Control Special
Functions that can be used
to
control the switches. (Special hnction 1.N is normally used to set the
amplifier gain in troubleshooting. This example was chosen
to
illustrate the concept of Direct Control
Special Functions because
of
its
simplicity.)
To
set the gain
to
8
dB,
key in
0.722
SPCL
or
.722
SPCL. The displays will show 0010 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 circuitry on the assembly
is
working properly, only switch Ull(3) should be closed, and thus
the signal is amplified by
8
dB.
Table 8-2. Programmable Gain Amplifier Switching Direct Control Special Functions
I
Direct Control
SDecial Function
0.720
0.724
0.722
0.721
Switch Gain
u1
l(4)
u1
l(1)
U1 l(3)
Notice that the display no longer shows a measurement result.
No
annunciators are lighted (except
REMOTE and ADDRESSED if the Special Function is entered via
HP-IB)
and only the SPCL key is
lighted. If any key other than a number key, the
S
(Shift) key,
or
the LCL key is pressed, the instrument
8-8
rev.20JUN87
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