Viva delta marker

Hi Shawn,

Using 1/deriv(wave1) in the outputs setup list works well, thanks for the suggestion.

In the case of a single marker, there is an expression property however I have not found any examples of how to use it. I tried setting the marker expression to 1/deriv(wave1) but it returns the following error.

ERROR (VIVA-6443):Illegal marker evaluation return type. Legal types: Bool, Int, Long, Double, Complex, String

This expression, abs(i("/Q0/B" ?result "dc")), returns the same error.

Do you know of any examples that show how to use the marker expression?

Regards,

Brad

Dear Brad RFeng,

Brad RFeng said:

Using 1/deriv(wave1) in the outputs setup list works well,

Thank you for letting me know - one step in the right direction for you anyway I hope!

Brad RFeng said:

In the case of a single marker, there is an expression property however I have not found any examples of how to use it. I tried setting the marker expression to 1/deriv(wave1) but it returns the following error.

ERROR (VIVA-6443):Illegal marker evaluation return type. Legal types: Bool, Int, Long, Double, Complex, String

This expression, abs(i("/Q0/B" ?result "dc")), returns the same error.

I believe the Expression defined in the GUI shown in Figure 1 needs to be a scalar. Your example 1/deriv(wave1) is a waveform and hence I wold expect an error message. In your second attempt, the expression also appears to be a waveform as the "dc" refers to a DC analysis and not a DC operating point (dcOp).

You might try something like the following scalar expression:

1/value(deriv(wave1) %X)

to annotate the inverted slope at the x coordinate of the marker (%X). I assume it will recognize the "%X" as the x coordinate.

You can verify this produces a scalar in the Calculator by entering a constant value for "%X" within the x range of your simulation and evaluate the expression. If that succeeds, copy that expression (with the constant value) to the marker Expression entry box in the GUI of Figure 1 and verify the Calculator result is also shown adjacent the marker in the ViVA window.

Shawn

Figure 1

There is no support for accessing the marker point (e.g. using %X, %Y) in the expression - all you can do is have a fixed expression that is then displayed using %E. I'm sure I've asked for this and have an enhancement request for it, but I can't find it right now (probably the wrong search terms - and I'm in a hotel on a slow internet connection so my capacity to search is a bit limited).

Similarly I have also asked in the past to be able to show the slope or tangent from a point marker (you can only show the slope on delta markers) - CCR 1061138.

There's no support for adding expressions of %S in the delta markers either.

Some of the challenge here is that potentially needing to evaluate an expression dynamically as you drag the marker could be expensive - imagine it doing some complex FFT type calculation - but it would be very helpful if this was possible. You should contact customer support and request the capability to have expressions that reference the marker location in the arguments.

The expression must return a scalar (as Shawn said) but that's not going to help you if you can't make it dynamic (well, you can just manually update the expression whenever you move it, I guess).

Andrew

Dear Andrew,

Andrew Beckett said:

There is no support for accessing the marker point (e.g. using %X, %Y) in the expression - all you can do is have a fixed expression that is then displayed using %E.

...

Andrew Beckett said:

(well, you can just manually update the expression whenever you move it, I guess).

Thank you for both reading my comments and taking the time to provide your insight and the information regarding the CCR for the tangent/slope for a point marker.  I was also thinking that a manual update of the expression might be possible in case the "%X" was not recognized as part of a valid expression.

I am sure Brad RFeng will find them helpful...at least I did anyway!

Shawn

Dear Andrew,

Andrew Beckett said:

There is no support for accessing the marker point (e.g. using %X, %Y) in the expression - all you can do is have a fixed expression that is then displayed using %E.

...

Andrew Beckett said:

(well, you can just manually update the expression whenever you move it, I guess).

Thank you for both reading my comments and taking the time to provide your insight and the information regarding the CCR for the tangent/slope for a point marker.  I was also thinking that a manual update of the expression might be possible in case the "%X" was not recognized as part of a valid expression.

I am sure Brad RFeng will find them helpful...at least I did anyway!

Shawn

Can a marker's x or y value be accessed in a design variable or global variable, something like myVar = VAR("M1")? 

Btw - using a marker's value in an expression has been possible in another simulation tool for a long time. I've created multiple plots on a display page that all update practically instantaneously when I drag a marker on the master plot. I have not tried doing that with an FFT but I suppose there is a limit on the response time.

Brad   

Brad,

In AWD (so a long time ago) you used to be able to get the value of a marker (I think this was just vertical markers) using the special variables M1, M2, M3 (these were just SKILL variables not design variables accessed via VAR()). This was deprecated in ViVA because it wasn't scalable, but the alternative (using %X, %Y in expressions) was not implemented. I found the CCR on this - 176826.

I've always wanted this behaviour (yes, other tools have such ability) and if used with care, interactive performance should be fine. That wasn't really the reason for it not being implemented - I suggest you request a duplicate of CCR 176826 be filed on your behalf.

Andrew