TABLE OF CONTENTS Here's what you're going to see in this chapter:
Close look at automated layout software
Why automated layout only works with certain cells
Knowing the circuit really does what it should
How to know in advance if your floorplan choice is good
Automated programs getting stuck
Troubleshooting tips
Which nets to wire first
Which nets to wire by hand
Techniques to guarantee rule-perfect layout
Flowchart of digital layout procedures
Lots of feedback loops
How to keep the power moving through big cells
Chicken or egg wiring and timing circle
Did you really build what you designed?
How to build quickie chips for testing
The majority of integrated circuits built today are large. I mean really huge CMOS digital chips. One chip might have literally millions of transistors in it. It's beyond any single mask designer's capabilities to lay out a chip like that by hand-in any reasonable time frame, at least. Consequently, the majority of large digital chips are laid out with the assistance of computer-aided tools.
Understanding how these automated digital layout tools operate allows you to develop skillful daily habits in your work-even in your analog work. If you understand how the software operates, you can lay out better circuits faster, compensate for software inadequacies, and steer clear of roadblocks before they happen.
Let's build a digital chip. In this chapter, we will follow...
