Tektronix, Inc. P6240, Руководство пользователя

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TLS 216 User Manual
3–23
Choosing a Group Display Mode
The TLS 216 Logic Scope displays the waveform groups you define in your
choice of three display modes: Analog, BusForm, and Timing Diagram. To
understand which mode to use for your application, you must first consider how
each mode affects the waveform data that a group displays on screen.
This article describes the three group display modes, how to identify the display
mode for any group, and how to select a new mode for a group. Also, this article
covers how to define group thresholds and set the display height for BusForm
and Timing Diagram groups.
To Understand Group Modes
To understand group display modes, consider how each mode displays
waveforms.
Analog displays each waveform in the group as the analog of its input signal. All
waveforms in the group have superimposed ground references. (See Figure 3-8.)
Unlike for the following modes, the logic scope scales Analog groups vertically
on screen when you use the Vertical SCALE knob. Also, the group reference
indicator for the group (left side of screen) points to the ground reference level
for the group in Analog mode if vertical offset is set to zero. Use Analog mode
to measure the actual response of a group of waveforms.
Analog mode is the only group display mode that can be switched between a
display of all the channels in a group and display of a single channel in a group.
BusForm displays each waveform in the group as one or more of three digital
logic levels defined as HIGH, LOW, or indefinite (between HIGH and LOW).
The level of each waveform displayed depends on how the instantaneous level of
its input signal compares with two threshold levels that you define. (See
Figure 3-8.) Use BusForm mode to measure the idealized response of waveforms
with respect to defined thresholds.
As with Analog mode, all waveforms in the group have superimposed ground
references. (The group reference indicator points to the midlevel for the group
instead of the ground level.) However, in BusForm mode the logic scope does
not display waveform height in volts/division but as a number of divisions
between the HIGH and LOW levels (group height) that you specify. (However,
see NOTE about clipping on page 3–28.) (See Figure 3-8.)
Timing Diagram displays each waveform in the group as one or more of three
digital logic levels like BusForm. However, unlike BusForm, the logic scope
vertically offsets the ground reference of each waveform, so that the waveforms
are separated vertically on screen. (The group reference indicator points to the