Synopsys Custom Compiler Automation

Why Automate Synopsys Custom Compiler?

Synopsys Custom Compiler is a full-custom IC design environment used by analog, mixed-signal, and RF design teams worldwide. While the graphical interface handles individual design tasks efficiently, automation through Tcl/Tk scripting unlocks the ability to execute complex workflows consistently, repeatedly, and without human error.

In production design environments, engineers routinely perform hundreds of repetitive operations per tape-out: instantiating devices with specific parameters, running DRC checks, applying fixes, generating reports, and preparing simulation testbenches. Manual execution of these tasks introduces variability and consumes engineering time that could be spent on actual circuit optimization.

Custom Compiler's scripting API exposes nearly every GUI function through Tcl commands, enabling teams to build robust automation libraries. Whether you are setting up a new PDK environment, creating parametric layout generators, or building batch verification flows, Tcl scripting is the backbone of productive Custom Compiler usage.

Custom Compiler Tcl/Tk Scripting Fundamentals

Custom Compiler uses an embedded Tcl interpreter with domain-specific commands organized into namespaces. The primary namespaces include ::cc for general design operations, ::le for layout editing, ::sch for schematic operations, and ::sim for simulation control.

A typical automation script begins by connecting to the running Custom Compiler session using cc::attachSession, then opens a cellview with cc::openCellView specifying the library, cell, and view names. From there, the script queries the design database using cc::getDb and cc::getDesign to access all design objects.

Instance iteration is done with cc::getInsts -cellView, which returns a list of all instances in the layout. Each instance can be queried for its master name with cc::getMasterName -inst and its origin coordinates with cc::getOrigin -inst.

The scripting environment supports standard Tcl constructs including loops, conditionals, procedures, and namespaces, alongside Custom Compiler-specific commands. Error handling uses catch blocks, and the built-in Tcl debugger allows step-through execution of complex scripts.

Key API categories include:

• Design navigation: cc::getDesign, cc::getInsts, cc::getNets, cc::getPins
• Layout editing: le::createRect, le::createInst, le::stretch, le::move
• Schematic editing: sch::createInst, sch::connect, sch::wire
• Verification: cc::runDRC, cc::runLVS, cc::runExtract
• Simulation: sim::createTestbench, sim::runSimulation, sim::getResults
• RISC-V EDA Tools Guide

Layout Automation Workflows

Layout automation is where Custom Compiler scripting delivers the highest return. Common workflows include device instantiation, guard ring generation, array creation, and automated DRC cleanup.

Parametric Device Instantiation allows engineers to place devices with calculated dimensions from a specification table. A procedure like instantiateDeviceArray accepts a list of device dictionaries containing the master name, width, length, finger count, and spacing. It iterates through each device, calling le::createInst with the calculated origin position and parameters such as W (width), L (length), and NF (number of fingers).

Guard Ring Automation wraps sensitive devices with substrate and nwell contacts. At advanced nodes, guard ring rules become complex with minimum enclosure, spacing, and layer requirements. A well-written script encodes these rules and applies them consistently across every sensitive device in the layout. The script calculates the bounding box of each target device, computes the guard ring placement coordinates based on foundry rules, and creates the appropriate diffusion and metal contacts using le::createRect and le::createInst.

DRC Auto-Fix Scripts parse DRC error databases and apply common fixes: widening metal traces to meet minimum width rules, extending vias for enclosure compliance, and removing antenna violations through diode insertion. These scripts typically reduce DRC error counts by 40-60% in a single pass, drastically reducing the number of manual correction iterations needed before tape-out.

Array Generation creates regular structures like capacitor banks, resistor arrays, and transistor fingers. The script calculates optimal placement for matching, symmetry, and common-centroid patterns, then generates the layout with proper routing between cells.

Simulation and Testbench Automation

Custom Compiler integrates tightly with Synopsys simulation tools including HSPICE, FineSim, and CustomSim. Tcl automation can generate simulation testbenches, sweep parameters, launch simulations, and collect results without manual intervention.

A common workflow automates corner simulation setup. A procedure like runCornerSweep accepts a design reference, a list of process corners (tt, ff, ss, sf, fs), and analysis configurations. For each corner, it creates a testbench with sim::createTestbench, adds the required analyses (DC, AC, transient, PZ) with sim::addAnalysis, and launches the simulation asynchronously with sim::runSimulation -async true.

The async launch pattern is critical for efficiency. Instead of running corners sequentially, all simulations start in parallel and the script uses sim::waitJob to block until each completes. A typical PVT sweep with 15 corners that takes 4 hours manually can complete in 45 minutes with parallel automation.

After all simulations complete, the script collects results with sim::getResults and performs automated comparison against specifications. Parameters like gain, bandwidth, phase margin, offset voltage, and power consumption are extracted and compared against pass/fail criteria. A summary report is generated showing which corners pass and which require design adjustment.

This approach is particularly valuable for PVT sweeps where dozens of corners must be simulated. Automation ensures identical testbench setup across corners and eliminates copy-paste errors in netlist modifications.

PDK Environment Setup Automation

Setting up a Process Design Kit in Custom Compiler involves configuring technology files, display resources, layer mappings, design rules, and extraction settings. For design houses working with multiple foundries or technology nodes, automating PDK setup eliminates configuration drift and reduces environment setup time from hours to minutes.

A PDK setup automation script typically handles the following tasks:

• Technology file loading: Using cc::loadTechFile to load the foundry-provided technology file that defines layers, purposes, and design rules
• Display configuration: Loading color and pattern files so all team members see consistent layer visualization across sessions
• Layer mapping: Ensuring correct GDSII stream number assignments for all layers and purposes to prevent export errors
• DRC rule deck binding: Linking the Pegasus, IC Validator, or Calibre rule deck path to the design environment
• Extraction setup: Configuring StarRC or xRC parasitic extraction settings for the target process node
• Library configuration: Setting standard cell and IP library search paths for correct component resolution

Teams that manage multiple PDKs benefit significantly from having a single script that configures the entire environment. For example, a design house supporting both TSMC 22nm and GlobalFoundries 12nm can switch between nodes by running a single setup command rather than manually reconfiguring dozens of settings. This eliminates the wrong-PDK-loaded class of errors that can waste days of layout work.

The script should also include validation steps: verifying that all referenced files exist, checking technology file syntax, and confirming that DRC rule decks load without errors. A common pitfall is a missing display resource file that causes Custom Compiler to use default colors, making it impossible to distinguish overlapping layers.

Building a Reusable Automation Library

The most effective Custom Compiler automation teams organize their scripts into a structured library rather than ad-hoc files. A well-organized library follows consistent naming conventions, includes documentation, and provides version control for tracking changes across tape-outs.

A recommended library structure separates concerns into core utilities, layout operations, schematic tools, simulation helpers, and PDK management. Each module should be self-contained with clear input and output contracts. Use Tcl namespaces to prevent naming collisions, prefixing all public procedures with a consistent namespace like ::cc_auto::layout for layout-related functions.

Document every public procedure with usage examples and parameter descriptions. A typical docstring pattern includes the procedure name, a one-line description, parameter list with types and defaults, return value, and a usage example. This documentation pays for itself when team members need to use automation written by colleagues.

Version control your automation library alongside your design data. Tag releases with tape-out milestones so you can reproduce the exact automation version used for any given submission. This practice also simplifies debugging when automation-related issues surface during design review or foundry feedback.

Consider building a configuration layer on top of your automation library. A central configuration file per project stores technology-specific parameters like minimum metal width, via enclosure rules, and guard ring specifications. Scripts read from this configuration rather than hardcoding values, making them portable across technology nodes without code changes.

SkyCadEda specializes in building production-grade automation libraries for Synopsys Custom Compiler environments. Our Tcl/Tk scripting services cover everything from one-off scripts to enterprise automation frameworks integrated with your existing design flow. Contact us at sales@skycadeda.com to discuss your automation needs.

Related Articles

• What Is EDA Automation?
• Cadence SKILL Scripting Guide
• CAD Infrastructure for Semiconductor
• PDK Setup and Enablement
• DRC/LVS Physical Verification
• ASIC Design Flow & Platform Support
• Tcl/Tk for EDA Automation
• Virtuoso Layout Automation
• GDSII OASIS Layout Automation
• FlexNet Licensing for EDA Tools
• Open Source EDA Tools Guide
• Advanced Node Verification
• Cloud EDA SaaS Solutions
• DFT Design for Test Automation
• Timing Closure Automation Guide
• Calibre SVRF TVF Rule Decks Guide
• Python EDA Automation Guide
• IP Porting and Migration Guide
• Mixed-Signal Verification Guide