Settling Time — Control Systems/Pulse Metrics

Settling Time

Control Systems / Pulse Metrics

Reports how long after a transition the waveform last strayed outside a tolerance band around the state level it was heading for – MATLAB's settlingtime:

s = t(last sample with |u − landing level| > (high − low) · tol / 100) − t(mid crossing)

The search runs over a settling region that opens when the transition completes and closes Seek Duration seconds after the transition instant. The instant itself is interpolated between the last straying sample and the one after it, so the answer is not quantised to the sampling period.

Ports

• u – the bilevel waveform to measure. Scalar – see Notes.
• s – settling time of the most recent closed region, in seconds from the transition instant, held until the next region closes. Scalar.
• lev – the level the waveform was at when it settled, in the signal's own units. Scalar. It is one tolerance band away from the landing state level, on whichever side the waveform approached from.
• ok – 1 when the most recent closed region produced a measurement and 0 where MATLAB reports NaN. Scalar – see Notes for the three cases that produce a 0.

Parameters

• Low State Level – the value the waveform sits at in its low state. 0 by default.
• High State Level – the value it sits at in its high state. 1 by default. Every threshold below is a percentage of the distance between these two, so they must differ.
• State Level Tolerance (%) – how far into the amplitude a sample must be before it counts as having settled into a state. 2 by default, the value IEEE Std 181-2003 uses. ⚠ It is also the settling band: settlingtime measures the stray against the same tolerance it uses for the state boundaries, so raising it loosens both at once.
• Mid Percent Reference Level – the level whose crossing dates a transition, as a percentage of the amplitude. 50 by default. The settling time is measured from that instant, not from the sample the transition completed on.
• Seek Duration (s) – how long the settling region lasts, measured in seconds from the transition instant. 0.1 by default. It is MATLAB's D argument, which that function requires rather than defaults. A region that ends before the waveform stops straying reports no measurement rather than a short one.
• Sampling Time (s) – zero or less inherits the solver's rate; a positive value runs the block at that period.

Code export

All ten targets: Python, MATLAB, Java, Rust, C, C++, VHDL, Verilog, SystemVerilog and PLC Structured Text.

Every threshold is structural and is inlined into the comparisons at export time rather than exposed as a tunable parameter. The Seek Duration is converted to a whole number of sample periods once, at export time, and the emitted core carries that count rather than the seconds – so re-export after changing the duration or the sampling period.

⚠ The three HDL targets are simulation-only. They carry this block's arithmetic in real rather than Q16.16, quantising only at the port boundary, for a reason specific to what it measures: an instant is a sample index plus a fraction, and a 16-bit integer part runs out after 32767 samples – five and a half minutes at a 10 ms rate. The comparisons and the interpolation are exact in real, which is what makes the exported core agree with the simulation.

Simulink bridge

No equivalent (Support::None). Measured rather than assumed: a find_system sweep over 22 DSP System Toolbox and Simulink libraries on R2026a finds no block matching duty, pulse, rise, fall, slew, overshoot, settling or state level – the whole Pulse Metrics group is MATLAB functions with no Simulink counterpart. The bridge reports this block rather than dropping it silently, and it therefore has no parity testbench. Code export verification still covers it across all ten languages.

Notes

• Stateful, and discrete by nature (setDiscreteOnlyBlock(true)): the tracker advances once per sample.
• The last STRAY sample is what is searched for, not the first settled one. A ring that re-crosses the band has many samples inside it and only one last sample outside it, and IEEE Std 181-2003 Sec 5.3.7 names the latter. The two agree on an edge that approaches its level once and differ on every ring.
• Three cases report ok = 0, and they are MATLAB's three NaNs. The waveform is still outside the band when the region expires; a later transition begins before it expires; or the region is shorter than the transition itself, so it expires before the transition even completed.
• s and lev hold when ok is 0, keeping their last real measurement, and both start at 0 before the first one exists.
• A measurement appears one sample after the region that produced it closes, in the live run and in all ten exported languages alike. A hardware block cannot read back a value it computes in the same clocked interval, so publishing immediately would put the three HDL targets one sample behind the other seven; the delay is uniform instead, and deliberate.
• The state levels are PARAMETERS here, not estimated from the data. MATLAB's pulse-metric functions call statelevels to guess the two levels from a histogram of the WHOLE signal when you do not supply them; that is a batch operation over samples a streaming block has not seen yet. This block takes the levels the way those same functions do when you pass 'StateLevels' explicitly.
• Scalar only. One waveform and its own tracker; wire one block per channel.
• No state space. The block is not linear in its input – it is a sequence of comparisons – so it carries none and model reduction correctly declines to merge it.
• Sibling readouts of the same tracker: Rise Time and Fall Time measure the transition itself, Overshoot and Undershoot measure how far past the level the waveform went, and this block measures when it stopped going past it.