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R & S E K 8 9 5 / R & S E K 8 9 6
User Manual
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Control Unit
1.3.4 Control Unit (R&S EK 896)
1.3.4.1 Design
The control unit consists of a mounting plate, a
keyboard (A2.2), a display (A2.3), a toggle
switch, a recessed jack>type socket as well as a
miniature loudspeaker.
The keyboard circuitry contains jumpers for
selecting the direction of rotation for the HF
control, interfaces to the carrier board, the
display, the jack>type socket and the
loudspeaker / switch as well as to the jack>type
socket in the power supply.
1.3.4.2 Functioning
(See Fig. 1.7)
The internal processes within the key decoder
are derived from a 4>MHz quartz oscillator.
The key decoder continuously monitors the key
matrix and the tuning knob. For this purpose, a
sampling signal is sent out in turns via the
sampling lines. If a key is activated, the
sampling pulse returns via the respective line
to the key decoder. The tuning knob consists of
an angular>momentum generator (24 steps /
revolution) and two Hall probes (= pulse re>
ceivers). As a result of the rotation of the
angular>momentum generator, pulses are pro>
duced in the Hall probes, which are evaluated
by the key decoder. In the case that to a spe>
cific key a secondary function is assigned, it is
activated by additionally actuating the SHIFT
key.
As soon as the key decoder receives a sampling
pulse or pulses from the Hall probes, the re>
spective message is sent via interrupt line IRQF
to the CPU in the processor. As a reaction, the
CPU inquires via the data bus the 8>bit data
item from the key decoder. The data item
contains the information which key or softkey
was activated or by how many increments the
tuning knob was turned clockwise or counter>
clockwise.
The information is processed within the CPU. If
the operator activates for example the BFO
key, the LED BFO will light up and the display
will change. Instead of the modulation mode,
type and time of control as well as the softkey
assignment, the display BFO_ kHz and the
cursor appear in the BFO field. For this change
on the display, the CPU sends 8>bit data items
via the data bus to the LCD drivers and a buffer
(A). Which driver becomes effective upon
which data item, is selected by the CPU via the
8>out>of>3 converter.
Also via the 8>out>of>3 converter the CPU
selects which 8>bit data item is taken over into
the buffer (B). The data item contains
information which of the receivers is switched
to local control. Thus the control unit permits
local control of up to three receivers RX1 to
RX3.
Receiver RX1 is locally controlled:
f The 3.0>VDC voltage from the IF / AF
processor (RX1) is fed via switch S1 and
jumper X11 to the HF control.
f The 3.75>VDC voltage from the IF / AF
processor (RX1) is fed via switch S1 and
jumper X12 to the HF control.
f The MGC voltage (0 to 120 dBo
V) set with
the aid of the HF control is fed via switch S1
to the IF / AF processor (RX1). The direction
of rotation of the HF control is selected by
means of jumpers X11 and X12.
f The signal AF1 from the IF / AF processor
(RX1) is routed via switch S1 to the AF
control.
The AF control is followed by an amplifier.
Provided that switch S2 is closed, the amplified
AF signal is forwarded to a loudspeaker. Simul>
taneously, the amplifier output is connected to
a jack>type socket as well as via the interface
AF OUT and a cable to another jack>type socket
in the power supply. To the jack>type sockets
headphones can be connected.
The 5>VDC voltage from the power supply
drives a green LED. Illumination of this LED will
indicate that the power supply is functioning
properly.
6164.0717.02_01
> 1.12 >
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