Theory of Operation
WFM700 Series Waveform Monitors Service Manual 1-7
The Audio board receives serial audio data in AES/EBU format from the
selected Input module, or from the AES I/O connectors if they are configured as
inputs. When configured as outputs, the AES I/O connectors supply AES/EBU
serial audio de-embedded from the selected video input. The selection of
extracted embedded audio groups takes place within the Input module.
AES/EBU signals from the selected source are processed to extract channel
status, validity, and parity bits. The audio data is examined for clip and mute
conditions, and word length (active bits) and peak values are determined. Audio
data is up-sampled to 192 kb/sec for further processing.
DSP processors compute audio level according to the configured level meter
ballistic. The CPU periodically polls the Audio Module to get the current audio
levels, and then draws the corresponding bars via the VGA controller. Other data
concerning audio (clip, mute, channel status etc) is communicated in a similar
fashion from the Audio Module to the CPU for display, data logging, or alarm
A DSP processor creates a Lissajous image that is periodically transferred
directly to the VGA controller via the PCI bus.
HAES 1-2 I/O / AES 3-4 I/O / AES 5-6 I/O / AES 7-8 I/O. Four AES/EBU
format, AES-3id compatible inputs or outputs. As outputs, they supply serial
audio de-embedded from the selected video input. As inputs, they can be
selected for complete processing and display in place of embedded audio.
The power supply module accepts line input voltages within the range of
100 VAC to 240 VAC. Anytime line input voltage is supplied to the power
supply module, a +5 V housekeeping supply is activated, providing power to the
front panel ON/STBY switch and to the Environmental Controller (EC) on the
Main Interface board. The EC continuously polls the front panel ON/STBY
switch. Pressing the front panel ON/STBY button instructs the EC to activate a
relay in the power supply module, activating the Main Power supply. The Main
Power supply provides +5 V, +3.3 V, +12 V and --12 V to the circuits and other
modules via the Main Interface board. The EC monitors all power supply
voltages and shuts down the Main Power supply if a problem is detected.
Figure 1--1 on page 1--8 is a block diagram of the signal flow of the instrument.
Figure 1--2 on page 1--9 is a block diagram of the control flow.
Audio Module (Option DG)
Power Supply Module