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2.1 Floorplanning

Just like our layout assignments, without a careful plan on how you actually put together your circuits,

can lead to hours of pain and agony. This is one of the great things about the stick diagram. One of the

ways to extend this to higher level designs, especially designs that utilize hierarchy, is to use floorplanning.

Floorplanning involves the simple diagramming of your circuit and how it gets put together.

As we learned in lecture, a stick diagram may help us to visualize the structure, but it does not help

us with the sizing. You can extend this by using pitch. Pitch is the distance, usually between two metals,

between each layer. There are various ways to measure the pitch, such as between the center of a metal and

its next edge. One way that you can incorporate this into your stick diagrams is to allow a 8 lambda pitch

between each contact. Of course, you will have to account for the minimal width of each diffusion region,

but it can help you with getting the dimensions of each cell.

Once you have a more or less idea of the size of your cell, you can use this to floorplan your layout. When

utilizing hierarchy, certain functions will use each other ostensibly. For example, an AND gate would utilize

an NAND and and inverter gate. How you put them together, would involve high-level floorplanning. In

other words, putting objects or blocks together and placing dimensions together to get an idea of the size

necessary. There may be many times when you have to floorplan your circuit to fit a certain size. Therefore,

the better the floorplan, the better the implementation. An example of a floorplan is shown in Figure 1.

Fig: 1