Tektronix TG8000 Service Manual

Mainframe theory of operation
Mainframe the
ory of operation
This section
describes the basic operation of the major circuit blocks or modules
in the TG8000.
To see diagr
ams that show the relationship between the major circuit blocks and
how the modules interconnect, refer to the Diagrams section. (See page 2-9.)
Main board
The Main board consists of the following seven blocks.
Processor core
The processor core consists of the CPU and all of its support circuits such as flash
memory,
DDR memory, clocks, buffers, reset circuit, configuration memory,
and decoder PLD.
The CPU
controls the front panel, LCD display, USB port, network interface, GPI
interface, and installed modules. The CPU also controls execution of remote
commands and downloading and uploading of signal files through the Ethernet
interface.
The flash memory holds the firmware data and signal data used to generate outputs
from some modules. During Genlock or GPS referenced operation, the CPU reads
data from the input module, and controls the frequency of the secondary clocks.
Ovenized oscillator
The ovenized oscillator provides the stable timebase for generating signals. This
is a fixed20MHzandisnotadjustable.
Video / Audio clocks
The synthesizer creates the video and audio clocks from the oven output. The
video clocks are a 54 MHz master clock signal and HD rate clocks of 74.25 MHz
and a 74.25/1.001 MHz. The audio clock is 12.288 MHz. The CPU can control
the ratio between the oven and these clocks. By controlling this ratio, the system
can lock to external signals for Genlock or GPS reference. The ratio is also
adjusted to achieve c alibration, with the resulting value stored in flash memory.
The 54 MHz and the 12.288 MHz are delivered to each slot. For the HD rate
clocks, the CPU controls four multiplexe rs that independently allow each slot to
get either the 74.25 MHz or 74.25/1.001 MHz clock. The diagnostics monitor that
each clock is correctly locked to the oven or master 54 MHz clock.
Frame pulse generator
The frame pulse generator uses the 54 MHz clock to generate the three frame
pulses at 2.997 Hz, 6.25 Hz, and 3.00 Hz that are used to synchronize the signal
formats generated by the installed modules.
TG8000 Multiformat Test Signal Generator Service Manual 2–7

Tektronix TG8000 Specifications

General

Brand	Tektronix
Model	TG8000
Category	Portable Generator
Language	English