Tag Archives: Skill

Shortcut to plot relative to reference signal

Ocean/skill script follows. Select a net. Press ctrl-g. Now that net is your “reference”. Select a different net (or the same net if you are fond of trivial signals). Press ctrl-r that second net is plotted relative to the reference. This is useful for debugging multiple supply domains, supply/ground bounce, and differential circuits. relVt.il:

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Creating a Nyquist plot with Cadence

Cadence has a stability analysis that returns loop gain (return ratio). Typically, this is done using a log sweep of frequency. The reason is that doing a uniform linear sweep results in too large frequency steps for low frequencies and/or too large of a step for higher frequencies. Unfortunately, when you do a logarithmic sweep, […]

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For loops in Cadence

If one is doing an analysis over a range of variables, one should use the paramAnalysis ocean function. That said, I’m constantly having to look up how to do a for loop in Skill. So, I’m placing a couple examples where I know I can get to them.

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Skill File I/O

I keep having to look up file I/O using Cadence’s SKILL language, so I’m putting it here for easy reference

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Non-Radix-2 FFT in Cadence/Ocean/Skill/Spectre | Using Cadence IPC to talk to Matlab (or anything else)

Introduction I had been working on a pulse-width-modulation (PWM) design. It was a pseudo-digital implementation, in that the output was clocked by a high-speed clock. The actual switching rate was much lower than this clock. I wanted to simulate this design in Cadence/Spectre by running a transient and then taking an FFT. However, I ran […]

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Pictorial introduction to using Cadence & Subversion

I previously blogged about some scripts I use to help Cadence & Subversion be more compatible. I received some feedback that the scripts were incomplete and came without any usage model. So, I went through an excercise to document the scripts and to make sure they were complete.

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Calculation of ADC SNR in Cadence Skill/Ocean

However, here’s how I compute SNR/SNDR from an FFT using Cadence Ocean/Skill.

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Getting subversion and Cadence to play nice

I wrote a set of scripts to make Cadence IC tools & Subversion work together. Note: this is not actual Cadence/Subversion integration (which is much more powerful and highly recommended). There were a few problems that I had to solve: Pesky .svn directories The main problem is that Subversion puts .svn housekeeping directories everywhere. When […]

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