To view analog signals, start the same way you start with other designs. Invoke Signalscan and select the File>Open Simulation File menu option. Signalscan supports opening and viewing of any number of digital and analog files simultaneously.

In the Design Browser window, select nodes by clicking on them. Select the Overlay Analog checkbox to view these nodes as a group of overlaid signals in the Waveform Window. Click on the AddToWave button to display these nodes in the Waveform Window.

In the Names Pane of the Waveform Window, you can select a node and use the middle mouse button to drag it into or out of a group or between groups. You can change the height of the wave display for an analog node or group of overlaid nodes. You can zoom and pan in an overlay group independent of other overlay groups or other stacked nodes. You can view nodes in an overlay group as stacked nodes, you can view analog nodes in digital form, you can perform various mathematical operations on nodes, and you can perform various measurements on a selected portion of a node.

Overlay Groups

Signalscan allows signals to be overlaid in the Waveform Window. A set of overlaid signals is called an overlay group . The Waveform Window can display both overlay groups and stacked signals at the same time, just as it can display both analog and digital signals at the same time. A single named group in the Names Pane of the Waveform Window can contain both stacked signals and one or more overlay groups. Any number of overlay groups can be created and displayed simultaneously.

Create an Overlay Group

To create an overlay group, either:

· In the Design Browser, first add signals to a group, and then select the Overlay Analog checkbox before you select the AddToWave button. The selected signals are added to the group overlaid on each other but not overlaid on any other signals or overlay group in that named group.

The Overlay Analog checkbox is selected by default if you use the -analog option when you invoke Signalscan. Deselect the Overlay Analog checkbox to load the signals in stacked mode. This preference can be saved to a configuration file (.do file).

· In the Names Pane of the Waveform Window, select one or more signals, and select the Edit>Overlay menu option. (Use the Shift or Ctrl keys along with the left mouse button to select multiple nodes. You can select nodes from different groups.) The selected nodes are displayed in an overlay group created at the insertion marker (yellow line) in the Names Pane.

Change Overlay Group Contents

You can move nodes into and out of overlay groups in the Names Pane of the Waveform Window. Select one or more nodes with your left mouse button, and use your middle or right mouse button to move them. If the insert position is completely inside an overlay group, the selected signals are added to the overlay group.

To add signals to the beginning of an overlay group, add them below the first signal and then move the top signal to a lower position in the group.

Convert Overlaid Signals to Stacked

To separate signals that are in an overlay group, select any node in the overlay group, and select the Edit>Stack menu option. All the signals in that overlay group are separated vertically in the group.

Printing Overlay Signals

Signals in an overlay group are printed either using different line patterns or different colors. See "Printing the Waveform Window".

Waveform Height Bracket

Analog waveforms have a bracket to the right of the variable name. Overlay groups have one height bracket for the entire group. To change the height of an analog waveform, move your cursor over the top or bottom of the bracket associated with the analog variable name or overlay group. The cursor changes to a double-headed vertical arrow. While the cursor is a double-headed arrow, hold down your left mouse button and drag the bracket up or down to the desired height. When you release the mouse button, the waveforms and the grid underlying the waveforms (if the grid is displayed — see "Grids") compress or expand to fit the new height. The minimum height of an overlay group is the height required to show the names of all the nodes in the group.

Analog Zoom and Pan

Analog signals and overlay groups have their own Y axis. Each can be panned independently of the Waveform Pane vertical scroll bar and can have a different Y zoom factor from other analog signals and overlay groups in the window. The X axis, however, is common to all nodes in the Waveform Pane. Zooming and scrolling the X axis for any signal scrolls all other signals in the Waveform Pane.

Vertical Zoom

You must select a signal in the Names Pane before you select ZoomInY , ZoomOutY , or ZoomOutYFull . If no signal is selected, these buttons and menu options are not enabled.

ZoomInY and ZoomOutY zoom by a factor of 2.

ZoomOutYFull is a convenient way to set the display of an overlay group to the minimum and maximum value of the overlay group. The minimum is the lowest value of all the variables in the overlay group, and the maximum is the highest value of all the variables in the overlay group.

You can access the Y zoom options from buttons or from the View>Zoom menu.

Horizontal Zoom

The time axis (X axis) is the same for all signals. When you select one of the X zoom options, everything displayed in the Waveform Pane zooms equally.

ZoomInX and ZoomOutX zoom by a factor of 2.

To zoom to a specific horizontal area, place Cursor1 (left mouse button) and Cursor2 (middle mouse button) around that area and then select View>Zoom>Between Cursors ( Ctrl+z ) or simply click your right mouse button.

You can access the X zoom options from buttons, from the View>Zoom menu, or by using keyboard shortcuts. Use Ctrl+i to zoom in, Ctrl+o to zoom out, Ctrl+f to zoom out full, and Ctrl+z to zoom between cursors.

Area Zoom

DAI Signalscan allows you to zoom to a specific rectangular area of an analog waveform or overlay group.

To define a rectangular area to zoom in on, hold down the Shift key while you press and drag your left mouse button. When you lift the mouse button, everything in the Waveform Pane is zoomed in X to the X values defined by your rectangle. Only the selected node or overlay group is zoomed in Y.

Panning

Panning is similar to zooming in that when you pan horizontally, all nodes in the Waveform Pane pan together in X, but each node or overlay group can be separately panned in Y.

To pan all nodes horizontally, use the left and right arrows on your keyboard or use the scroll bar at the bottom of the Waveform Pane.

To pan all nodes together vertically, use the up and down arrows on your keyboard or use the scroll bar on the right side of the Waveform Pane.

To pan a single node or overlay group vertically, first select a variable in the Names Pane. To vertically pan an overlay group, you only need to select one variable in the overlay group. Then hold down the Shift key while you press the up and down arrows on your keyboard.

Analog Views

Grids

Select the View>Grid menu option to enable or disable displaying a labeled grid behind your waveforms. The grid width is automatically determined by Signalscan. Signalscan tries to use round numbers to label the grid. The option to display the grid or not can be saved into a configuration file (.do file).

Data Points

By default, the analog waveforms are displayed as lines. Use the View>Analog Display Mode menu to display the analog waveforms as Points , Lines , or Points and Lines . All analog waveforms in the Waveform Pane are displayed in the selected mode. This display mode can be saved in a .do file.

Saving Analog Configurations

Group content (including expressions), overlay analog setting, grid setting, display mode, and zoom settings can be saved into a configuration file (.do file). The current view can be reproduced by reading the configuration file ( File>Execute Do-File ).

Analog-to-Digital Conversion

You can convert any analog variable to a single-bit digital value by specifying threshold values. Similarly, you can convert a set of analog variables to a digital bus. Use the Create Bus dialog for both of these operations, as described below.

Using the Create Bus Dialog

Use your middle mouse button to put the insertion marker where you want the new signal or bus to be. Select one or more analog variables in the Names Pane of the Waveform Window. Select the Edit>Create>Bus menu option or enter Ctrl+w . The Make Bus From Selected Variable(s) dialog box displays as shown in Figure 8-1.

Figure 8-1. Analog-to-Digital: Create Bus Dialog

This dialog box is the same as the one shown in Figure 4-2 except that this one has space to enter one or two threshold values. These threshold fields appear only if you have selected one or more analog variables. Notice the units (V ) associated with the threshold values. The other features of the Make Bus dialog work the same as for digital signals (see "Using Buses").

You can specify one or two threshold values. If you specify only one threshold value, then any of the original analog values that are less than the specified threshold value are converted to 0 in the digital result, and any values greater than or equal to the specified threshold are converted to 1.

If you specify two threshold values, then any of the original analog values that are less than the smaller of the two specified threshold values are converted to 0, any of the original values that are greater than or equal to the larger of the two threshold values are converted to 1, and any other values are converted to x (any of the original values that are less than the larger threshold value and greater than or equal to the smaller threshold value).

If you perform analog-to-digital conversions and then save your configuration in a Do-File, you will see these conversions defined by atod functions in the .do file. If you want to script analog-to-digital conversions directly in a Do-File, use the atod (analog to digital) function as described below.

Expressions

To display the value of an expression as a variable in the Waveform Window:

1. Use your middle mouse button in the Names Pane to put the insertion marker where you want the new variable to be.
2. Select the Edit > Create > Expression menu option. The Create Expression dialog displays as shown in Figure 8-2.

Figure 8-2. Create Expression Dialog

3. Optionally, enter a name for the new variable that will be created in the Enter Expression Name field. If you do not enter a name, the expression itself (whatever you enter in the Enter Expression field) is used for the expression name in the Names Pane of the Waveform Window.
4. Enter an expression in the Enter Expression field using any combination of the operations listed in Table 8-1:

Table 8-1. Analog Expression Operations
+ x	– x	x + y	x – y
x * y	x / y	x % y	x ** y
x < y	x <= y	x > y	x >= y	x == y	x != y
abs(x)	acos(x)	asin(x)	atan(x)	atan2(y,x)	atod(x,y[ units ][,z[ units ]])
cos(x)	cosh(x)	exp(x)	hypot(x,y)	log(x)	log10(x)
sin(x)	sinh(x)	sqrt(x)	tan(x)	tanh(x)

5. Click the OK button on the Create Expression dialog. The new variable is displayed at the insertion marker.

If all variables used in an expression are not currently viewed in the Waveform Window, the resulting expression will not have a smooth drawing.

Except for >, >=, <, <=, ==, and !=, expressions are evaluated only at the data points of the expression operands. If you are operating on a signal whose value changes infrequently, or if you zoom in far enough, the result after you apply certain expressions may not be the smooth curve you expected.

Variables — Escaping Special Characters

If a variable name used in an expression contains special characters, escape the special characters by entering a backslash in front of the variable name, and then put a space character after the variable name to stop the escape and correctly interpret any remaining parts of the expression. For example:

abs(\N1(v) )

This escape mechanism is the same as the Verilog escape mechanism.

Constants — Units

If you use a constant value in your expression, you may append an abbreviation for units, such as s , ns , V , or mV .

The power (** ) and square root (sqrt ) operations result in the removal of units from the operands.

Expressions in a Do-File

To use an expression in a Do-File, enclose the expression in double quotation marks and use it in place of a variable name. For example:

add group A "atod(X1.XI26.PL2,0.6V,2.7V)"

Expression Example

Analog to Digital (atod) Function

You can convert any analog variable to a single-bit digital value by using the atod (analog to digital) function.

When you are using the Signalscan GUI, it is much easier to use the Edit>Create>Bus dialog (see "Using the Create Bus Dialog") to convert analog to digital. You might want to use the atod function in a Do-File (see "Expressions in a Do-File" above).

The syntax of the atod function is:

atod( variablename , threshold1 [ units ][, threshold2 [ units ]])

If you use the atod function and the analog value you are converting has units associated with it, then you must specify units for the threshold value(s). The threshold value units must be compatible with the analog value units.

Figure 8-3 shows an example of using the atod function in the Create Expression dialog.

Figure 8-3. Analog-to-Digital: Create Expression Dialog

Measurements

Signalscan can perform several measurements on your analog signals. See the selections at the bottom of the View menu.

Value

Select one or more variables in the Names Pane of the Waveform Window. Position Cursor1 and Cursor2. Select the View > Value at Cursors menu option. For each selected variable, the values at Cursor1 and Cursor2 and the difference between those values are displayed. If you move the cursors, these values are updated accordingly.

Figure 8-4. Value at Cursors

Slope

Select one or more variables in the Names Pane of the Waveform Window. Position Cursor1 and Cursor2. Select the View > Slope For Values at Cursors menu option. For each selected variable, the slope between the two points defined by Cursor1 and Cursor2 is shown. If you move the cursors, the slope is recalculated accordingly.

Figure 8-5. Slope For Values at Cursors

Minimum, Maximum, and Peak-to-Peak

Select one or more variables in the Names Pane of the Waveform Window. Position Cursor1 and Cursor2. Select the View>Min/Max/Peak-to-Peak Between Cursors menu option. For each selected variable, the minimum, maximum, and peak-to-peak values are shown for the area between Cursor1 and Cursor2. If you move the cursors, these values are recalculated accordingly.

Figure 8-6. Min/Max/Peak-to-Peak Between Cursors

Rise/Fall Time

Select one or more variables in the Names Pane of the Waveform Window. Position Cursor1 over a rising or falling edge of the variable. Select the View > Rise/Fall Time at Cursor1 menu option. The rise or fall time is calculated for each selected signal at Cursor1, using user-specified values and thresholds. For the rise or fall time to have a value, the signal's value at Cursor1 needs to fall between the specified thresholds. Specify thresholds by editing the Low Threshold and High Threshold fields and then selecting the Apply button.

Figure 8-7. Rise/Fall Time at Cursor1

Average and RMS

Select the View > Average Values Between Cursors or the View > RMS Value Between Cursors menu option. The values between Cursor1 and Cursor2 are used to determine the average and RMS values. If you move the cursors, these values are recalculated accordingly.

Figure 8-8. Average Values Between Cursors

Figure 8-9. RMS Value Between Cursors

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DAI Signalscan User's Guide

CHAPTER 8 Analog Features

Overview