Mosis

Page from CMOS Circuit Design, Layout, and Simulation, Second Edition By R. Jacob Baker, Copyright Wiley-IEEE

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CMOS Circuit Design, Layout, and Simulation

1.2 Using the LASI Program
The LASI program discussed in this section can be used for the layout and design of CMOS integrated circuits. This section provides a brief tutorial covering the use of LASI. We assume that the reader hasdownloaded and installed LASI and the MOSIS setups following the instructions at cmosedu.com. We use the MOSIS setups (with a design directory of, for example, C:\Lasi7\Mosis) for our examples in this section. 1.2.1 The Basics of LASI A chip design should reside in a design directory. The LASI system executables are located in C:\Lasi7 (which cannot be used as a design directory). Information onsetting up a design directory can be found at cmosedu.com. Starting LASI Going to the Window’s start button, then Lasi 7, and then MOSIS results in LASI starting, Fig. 1.6. Notice how, at the top of the window in Fig. 1.6, the design directory (Folder) is shown. The menu items (Help, Run, Print, etc.) are executable by either clicking on the word (e.g., Help) or on the menu button (e.g., the pictureof a question mark). The buttons on the right of the display can be toggled by either pressing the Menu1 or Menu2 buttons or by clicking the right mouse button while in the drawing area. We’ll talk about the items on the bottom of the screen in a moment.

Figure 1.6 Starting LASI using the MOSIS setups.

Page from CMOS Circuit Design, Layout, and Simulation, Second Edition By R. Jacob Baker,Copyright Wiley-IEEE

Chapter 1 Introduction to CMOS Design Getting Help

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The LASI layout system comes with a complete on-line manual. This manual is accessible, while LASI is running, by pressing F1 on the keyboard and clicking the command button (simultaneously) with which the user needs help or by pressing the Help button. Alternatively, the user can open the help file in thedirectory C:\Lasi7\help without LASI running. Cells in LASI I Complex IC designs are made from simpler objects called cells. A cell might be a logic gate or an op-amp. When LASI starts-up, as seen in Fig. 1.6, the last cell loaded (prior to exiting LASI) appears in the load cell window. In Fig. 1.6, this cell’s name is “ALLMOSIS.” Let’s create a new cell called “test” with a rank of 1. Figure 1.7 showsthe resulting LASI screen. Notice that the current cell’s name and rank are displayed at the top of the window. If we want to load or create a different cell, we press either the Load menu item or the corresponding picture, as indicated in Fig. 1.7. The drawing area in Fig. 1.7 shows a reference indicator (the origin of the drawing). To toggle displaying this indicator, we can either press r on thekeyboard or the R button in the lower right corner of the display followed by redrawing the cell. To redraw the cell, we press Enter on the keyboard or Draw or the picture of the pencil at the top of the window.
Cell name and rank Load or create a cell (clicking on the word or picture results in the same action)

The mouse can be toggled between a cross and and crosshairs by pressing the tabbutton.

Reference marker (drawings origin) Toggles display of the reference marker

Location of the mouse

Figure 1.7 Screen after making a cell called "test" with a rank of 1.

Page from CMOS Circuit Design, Layout, and Simulation, Second Edition By R. Jacob Baker, Copyright Wiley-IEEE

8 Navigating

CMOS Circuit Design, Layout, and Simulation

Pressing the Grid button on the rightof the screen followed by zooming in around the reference indictor by pressing Zoom (and two clicks of the mouse to indicate the zoom area) on the top menu may result in a screen like the one seen in Fig. 1.8. The reader should experiment with the Fit (alt+f), Xpnd (alt+x or expand), and the arrow (Left, Up, Dn, and Right) commands. The center command, Cntr, centers the screen around a point set...