Tektronix WFM5250, Service Manual

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Theory of Operation
Recursion and Picture
Processing Engine
The output of the rasterizing engine feeds the picture and recursive processing
engine in the second large FPGA. This engine adds the previous frame to the
present frame to reduce
fl icker and improve brightness. It also converts the picture
and waveform signals from various input frames rates to a 60 Hz frame rate in
order to work with the DVI-I monitor. The picture and waveform data are then
combined with the graphics and audio bar information from the control processor.
The result is presented on the LCD display, and sent through the DVI connector
to the external monitor.
CPU Board
CPU Board Control
Processor
The control processor is in charge of all the operational modes in the instrument.
It communicates with the FPGAs on the FPGA board through a parallel peripheral
bus; it communicates with the front panel, and controls most other internal
devices, though either the SPI or the I
2
C bus.
The control processor interfaces to the Ethernet through a dual rate connection.
This allows the network connection to run at 10 or 100 MBps.
Front Panel
The front panel contains a small processor that communicates with the control
processor through SPI signaling. Reprogramming can be done through the SPI if
the front panel processor
fl ash code must be updated.
Audio (Option AUD)
The audio software option enables display of the levels and phase of embedded
audio, and drives the headphones output.
SDI Audio Processing The display FPGA extracts embedded audio data from the selected SDI data
stream and sends it to the headphones output D/A converter on the CPU board.
The FPGA also calculates the peak values for the selected meter ballistics
(response characteristics).
The audio data has two paths to the display. On one path, peak values are read
by the control processor, which then plots the bar and surround displays. On the
second path, raw data samples are sent to the waveform processing engine, which
interpolates and plots it to generate the Lissajous, or “phase,” display.
HDMI Audio Processing
HDMI audio is extracted from the HDMI stream by the HDMI input IC. It is then
output via an I2S interface to the FPGA board, where it enters the DSP FPGA.
Once on the FPGA board, the audio is processed in a manner similar to the SDI
audio.
6 WFM5250 Waveform Monitor Service Manual