entity my_and is
port (a, b : in std_logic;
c : out std_logic);
architecture my_and_arc of my_and is
c <= a and b;
VHDL (VHSIC-HDL, Very High-Speed Integrated Circuit Hardware Description Language) is a hardware description language used in electronic des...
Netgen version 1.3 is the stable branch and has been essentially unchanged for several years. The development branch version 1.4 is an attempt to bring netgen up to par with the industry-standard Calibre tool from Mentor Graphics. Since (as far as I know) all LVS tools are based on the same class partitioning algorithm, this effort is not as difficult as it may seem. Mostly, netgen must be made to properly understand hierarchy, device properties, and generate a more readable output. All these changes are now underway (as of November 2007, when the development version 1.4 branch was created).
Netgen was developed independently of magic, written by Massimo Sivilotti, and eventually incorporated into the beginnings of the Tanner L-Edit suite of tools. However, the original code was left open source, and so I have incorporated it into the Tcl-based suite of tools including magic, IRSIM, and xcircuit.
IRSIM shares a history with magic, although it is an independent program. Magic was designed to produce, and IRSIM to read, the ".sim" file format, which is largely unused outside of these two programs. IRSIM was developed at Stanford, while Magic was developed at Berkeley. Parts of Magic were developed especially for use with IRSIM, allowing IRSIM to run a simulation in the "background" (i.e., a forked process communicating through a pipe), while displaying information about the values of signals directly on the VLSI layout.
For "quick" simulations of digital circuits, IRSIM is still quite useful for confirming basic operation of digital circuit layouts. The addition of scheduling commands ("at", "every", "when", and "whenever") put IRSIM into the same class as Verilog simulators. It is, in my opinion, much easier to write complicated testbench simulations using Tcl and IRSIM. I have used IRSIM to validate the digital parts of several production chips at MultiGiG, including the simulation of analog behavior such as PLL locking.
IRSIM version 9.5 was a long-standing and stable version that corresponded to the relatively stable Magic version 6.5. When magic was recast in a Tcl/Tk interpreter framework (versions 7.2 and 7.3), IRSIM could no longer operate as a background process. However, it was clear that if IRSIM could also be recast in the same Tcl/Tk interpreter framework, the level of interaction between it and Magic would be greatly increased.
I set about to create the "new" IRSIM, although it came along in fits and starts as I had time to work on it. Because the original "analyzer" graphic display window (and GUI, to a very limited extent) was written in Xt (the rather primitive window system that is an integral part of X11), it was scrapped for a while. In its place, I substituted graphs in "Blt" based on the same in "tclspice" (see SourceForge for the tclspice project). Unfortunately, "Blt" insists that all data vectors must be real-valued, which is 1) a severe waste of space for binary digital values, and 2) is unable to represent the concept of an "unknown" value that is so crucial to fast switch simulation. So, eventually I was forced to scrap BLT and actually sit down and code out a real Tcl-based analyzer window and GUI. The result is finally done in revision 9.7.3.
XCircuit is a UNIX/X11 (and Windows, if you have an X-Server running, or Windows API, if not) program for drawing publishable-quality electrical circuit schematic diagrams and related figures, and produce circuit netlists through schematic capture. XCircuit regards circuits as inherently hierarchical, and writes both hierarchical PostScript output and hierarchical SPICE netlists. Circuit components are saved in and retrieved from libraries which are fully editable. XCircuit does not separate artistic expression from circuit drawing; it maintains flexiblity in style without compromising the power of schematic capture.
The ElectricTM VLSI Design System is an open-source Electronic Design Automation (EDA) system that can handle many forms of circuit design, including:
The Electric VLSI Design System is a highly flexible and powerful system that can handle many different types of circuit design (MOS, Bipolar, schematics, printed circuitry, hardware description languages, etc.) It handles geometry at any angle (not just Manhattan) and can even handle curves.
Layout is done by placing and wiring electrical components. Although this is standard practice for schematics, it is unusual for chip layout. However, because of this style of design, Electric understands chip layout at a more sophisticated level, and can aid in design to an unprecedented degree.
Electric has many analysis tools, including design-rule checking, simulation, and network comparison. Electric has many synthesis tools, including routing, compaction, silicon compilation, PLA generation, and compensation.
The user interface is quite sophisticated and runs on all popular workstations (Windows, Macintosh, and UNIX). It also provides interpretive languages for advanced users.
The software is freely available at www.staticfreesoft.com