PCB, the A16 CPU Interface PCB, and the optional
A13 10 MHz DDS PCB.
The CPU is indirectly linked via the A16 CPU Inter-
face PCB to the A3 Reference Loop PCB, the A4
Coarse Loop PCB, the A5 Fine Loop PCB, and the
A6 Square Wave Generator PCB. The A16 PCB
contains circuitry to perform parallel-to-serial and
serial-to-parallel data conversion. It also contains
circuitry for many of the rear panel signals, a 13-bit
resolution DVM, and decoder circuitry for the front
panel rotary data knob optical encoder.
Front Panel
This circuit subsystem consists of the the A1 Front
Panel PCB, the A2 Front Panel Control PCB, and
the Liquid Crystal Display (LCD). This subsystem
interfaces the front panel LCD, LEDs, and keys to
the CPU via the dedicated data and address bus.
The front panel rotary data knob is indirectly linked
to the CPU via the A16 CPU Interface PCB.
The A1 Front Panel PCB contains the keyboard
matrix of conductive rubber switches. The A2 Front
Panel Control PCB has circuits to control the LCD
dot-matrix display, turn the front panel LEDs on
and off, and convert keyboard switch matrix signals
to parallel keycode. It also contains the standby/
operate line switch logic circuit and the optical en-
coder for the rotary data knob.
Frequency
Synthesis
The frequency synthesis subsystem consists of the
A3 Reference Loop PCB, the A4 Coarse Loop PCB,
the A5 Fine Loop PCB, the A7 YIG Loop PCB, and
the A11 FM PCB. It provides the reference frequen-
cies and phase lock circuits for precise control of the
YIG-tuned oscillator frequencies, as follows:
q
The A3 Reference Loop PCB supplies the sta-
ble 10 MHz, 100 MHz, and 500 MHz reference
frequency signals for the rest of the frequency
synthesis system.
q
The A4 Coarse Loop PCB generates coarse
tuning frequencies of 202.5 to 990 MHz for use
by the YIG Loop.
q
The A5 Fine Loop PCB provides fine tuning
frequencies of 30 to 40 MHz for use by the YIG
Loop.
2-4
690XXB/691XXB MM
FUNCTIONAL
690XXB/691XXB
DESCRIPTION
MAJOR SUBSYSTEMS
Summary of Contents for 680 C Series
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