Tektronix WFM700 Series, Service Manual

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Theory of Operation
1- 6
WFM700 Series Waveform Monitors Service Manual
The CPU board receives commands from the Front Panel (buttons, knobs, and
touch screen) via RS232 connections, then transmits instructions to the other
modules via the PCI bus and Serial bus. The CPU also defines the operation of
the video channels (but is not in the video signal path). All text and graticule
information for the LCD panel is generated by the CPU board and sent to the
LCD via the VGA Mux on the Main Interface board.
External Connectors
H
REMOTE. 9 pin subminiature D-type connector used as a Ground Closure
interface for remote control.
H
USB. This connector is not used and was removed for CPU board versions
671-4528-04 (SN B019999 and below) and 671-5751-03 (SN B024089 and
above).
H
ETHERNET. (10/100 Base T). 10/100 Mbit/sec Ethernet interface. Used for
downloading firmware upgrades.
Real Time Display board receives the parallel digital video signal from the Input
module and processes the video data to display the information in various forms
on the raster display. The different forms of display consist of sweeps (overlay or
parade), x y (vectors, lighting, diamond, ect.), and picture monitor. The RTD
board handles either standard definition (SD) or high definition (HD) data. Only
one channel is processed at a time.
The RTD is divided into two logical sections. The first section, the DSP engine,
performs signal processing and routing operations to create standard waveform
monitor displays. The second section, the rasterizer engine, performs attack and
decay operations to simulate an analog CRT phosphor screen. The rasterizer also
has the ability to partition multiple displays into separate windows.
The RTD accepts a 10 or 20-bit data stream (SD or HD) from either of two input
slots. A polyphase interpolator increases the data rate and fills gaps in the data.
The higher data rate allows the rasterizer to plot more pixels per second to
improve the display quality. The Measurement Processing block produces
various waveform displays such as Parade, Vector, and Diamond and also
performs gain, offsetting, and filtering operations. It outputs pairs of numbers
used by the Rasterizer and its companion memory to build a display map.
Memory values are incremented or decremented depending on these number
pairs, varying pixel display brightness according to frequency of occurrence,
similar to a phosphor screen. A Picture Mode Processing block allows a raster
picture display of the input signal, suitably adjusted to the 640x480 VGA display
format. The Rasterizer output is applied to the color LCD display after it is
combined with any text and graticules from the VGA controller.
CPU Board
Real Time Display (RTD)
Board