Inconsistent evaluation/plotting of phase-correction expressions in ADE Assembler vs. Calculator (IC23.1-64b.43)

Hello,

I am observing inconsistent behavior between the Virtuoso Calculator and ADE Assembler result evaluation when trying to unwrap the phase from an STB analysis so that it starts at +180° and can be used conveniently for phase-margin and gain-margin calculations.

Goal

From an STB analysis I obtain loop gain phase:

phase0 = phase(getData("loopGain" ?result "stb"))

Because the phase may start at −180° (or 180° ± n·360°), I compute a correction term so the low-frequency phase starts at +180° and downstream calculations (e.g., cross() for phase margin) are straightforward.

Solution 0 (works numerically, but cannot be plotted from Results)

phase0 = phase(getData("loopGain" ?result "stb"))
phase_correction = (360 * round(((180 - value(phase0 firstVal(phase0))) / 360)))
phase = (phase0 + phase_correction)

Observed behavior

• ADE Assembler recognizes phase as a waveform (wave icon shown in Outputs/Results).

• Downstream expressions using this phase (e.g., cross() for phase margin) evaluate correctly.

• However, double-clicking the waveform to plot fails with:

*Error* ("round" 0 t nil ("*Error* round: argument #1 should be a number (type template = "n")" srrWave:0x49863400))

ERROR (ADE-1057): Could not evaluate expression
        Name:'phase_correction'
        Expression:'(360 * round(((180 - value(phase0 firstVal(phase0))) / 360)))'
     because of the following error(s)
        ("round" 0 t nil ("*Error* round: argument #1 should be a number (type template = "n")" srrWave:0x49863400))
     Ensure that the definition of the expression is correct.

*Error* ("round" 0 t nil ("*Error* round: argument #1 should be a number (type template = "n")" srrWave:0x498634c0))

ERROR (ADE-1057): Could not evaluate expression
        Name:'phase_correction'
        Expression:'(360 * round(((180 - value(phase0 firstVal(phase0))) / 360)))'
     because of the following error(s)
        ("round" 0 t nil ("*Error* round: argument #1 should be a number (type template = "n")" srrWave:0x498634c0))
     Ensure that the definition of the expression is correct.

*Error* ("plus" 0 t nil ("*Error* plus: can't handle (srrWave:0x49863420 + unbound)"))

ERROR (ADE-1057): Could not evaluate expression
        Name:'phase'
        Expression:'(phase0 + phase_correction)'
     because of the following error(s)
        ("plus" 0 t nil ("*Error* plus: can't handle (srrWave:0x49863420 + unbound)"))
     Ensure that the definition of the expression is correct.

So the expression behaves as:

• Valid for numerical post-processing

• Invalid for plotting

Solution 1 (Calculator plots OK, but ADE output gives eval error)

As a workaround I modified the correction:

phase_correction1 = (360 * round(((180 - ymax(value(phase0 firstVal(phase0)))) / 360)))
phase1 = (phase0 + phase_correction1)

Observed behavior

• In the Virtuoso Calculator, plotting phase1 works correctly.

• When defined as an ADE Assembler output, it results in eval err after simulation.

So this case behaves as:

• Valid in Calculator

• Invalid in ADE output evaluation

Confusion / Question

These two cases appear inconsistent:

This makes it difficult to determine:

• what data types (number vs. wave) are actually expected by round(), value(), ymax(), etc.

• why ADE can use a waveform expression for further calculations but cannot plot it

• what the recommended method is to unwrap STB phase to start at +180° in a way that is:

  • numerically robust

  • plottable

  • ADE-compatible

Questions

1. Is this inconsistent behavior between Calculator, ADE evaluation, and ADE plotting expected?

2. Is there a Cadence-recommended method to unwrap STB phase to +180°?

3. Could this indicate a bug in ADE expression evaluation or plotting?

Environment

Cadence IC version: IC23.1-64b.43
Analysis: STB in ADE Assembler

Any clarification or recommended best practice would be greatly appreciated.

Thank you.
Can