Tektronix 410, Service Manual

Page: 66 / 275

Circuit Description
Theory of Operation
3Ć2
Attenuators
— Circuitry in the attenuator selects the input coupling, the
termination, and the attenuation factor. The processor system controls the
attenuators. For example, if 50
W
input termination is selected and the input is
overloaded, the processor system switches the input to the 1 M
W
position.
The preamplifier in the A05 Attenuator amplifies the input signals.
Probe Coding Interface
— Probe coding interface signals pass through
the A06 Front Panel to the processor system which in turn controls the
A05 Attenuator and the A04 Acquisition boards.
Jumper
— Signals from the attenuators pass through the A08 Jumper board
to the acquisition system.
Acquisition System
— The acquisition system converts the input signals
to digital signals and controls the acquisition process under direction of the
processor system. The acquisition system includes the trigger, acquisition
timing, and acquisition mode generation and control circuitry.
D1 Bus
— The acquisition system passes the digital values representing the
acquired waveform through the D1 bus to the A09 DSP board (TriStar). This
happens after a waveform acquisition is complete if the digital signal proces-
sor (DSP) requests the waveform.
Processor System
— The processor system consists of a 68020 micro-
processor that controls the entire instrument. It includes the firmware program
for the oscilloscope. The firmware can be reprogrammed by using the GPIB
and an external software package. The processor system also includes a
GPIB interface.
DSP
— The digital signal processor processes each waveform as directed by
software downloaded from the system processor. Waveforms and any text to
be displayed are passed on to the A02 Display board.
Display
— Text and waveforms are processed by different parts of the
A02 Display circuitry. The display sends the text and waveform information to
the A26 Monitor assembly as a video signal. The display circuitry also gener-
ates and sends vertical (VSYNC) and horizontal (HSYNC) sync signals to the
A26 Monitor assembly. A VGA-compatible video output is available at the rear
of the instrument.
Monitor Assembly
All information (waveforms, text, graticules, and pictographs) is displayed by
the A20 CRT Driver. The driver generates the high voltages necessary to
drive the CRT. It also contains the video amplifier, horizontal oscillator, and
the vertical and horizontal yoke driver circuitry. The monitor gets its supply
voltages from the A25 Low Voltage Power Supply through the A01 Backplane
and the A07 Auxiliary Power boards.