Tektronix WFM5250, Service Manual

Page: 21 / 57

Theory of Operation
Video I/O Board
Serial Digital Input
Processing
The serial digital circuitry receives the SDI input streams from the Video I/O
board after they have been equalized. The SDI input streams are passed to the
DSP FPGAs where they undergo measurement and raster processing. The signal
information is then passed to the DSY FPGA for picture processing, recursion,
and display combining. The result is shown on the LCD display, and also provided
to the external DVI-I connector.
HDMI Input Processing Both HDMI inputs (HDMI 2A and HDMI 2B) are routed to the input IC, where
one of the two inputs is decoded. The decoded video is then routed to both the
HDMI output IC and the DSP FPGA on the FPGA board. On the FPGA board,
the DSY and DSP FPGAs process the data in a similar manner to the SDI data.
REF I/O Board
Reference Input The reference input is a passive loopthrough, which is AC coupled and buffered.
The reference signal is applied to a sync separator whose output is supplied to the
DSP FPGA, where the timing information is derived. The reference signal is also
digitized for display as a waveform.
LTC LTC inputs come from the remote connector. The LTC signal is applied to an A/D
converter and then input to the waveform processing FPGA, which decodes the
time code information.
NOTE.
The FPGAs decode VITC signals digitally.
FPGA Board
Digital Waveform
Processing Engine
The data streams from the video inputs are applied to the waveform processing
FPGA. This block deformats, up-samples, interpolates, and otherwise processes
the data to generate the signals needed to create the displays.
Rasterizing Engine The rasterizer engine resides in the same DSP FPGA as the waveform processing
engine. This block builds up the variable intensity images in the fast static RAM.
For each pixel of the display, the rasterizer engine increments the intensity of that
pixel every time the waveform hits its coordinates. As a result, the waveform
areas that are hit more frequently are brighter. For any given frame, the intensity
map is built up in one memory chip and read out of the other. The functions
swap on the next
fi eld.
WFM5250 Waveform Monitor Service Manual 5