Pin Assignment 1. 2 90 Pins 90 Connections 90 Pins Assign all nets to unique pin locations −such...

Pin Assignment

1

2

Pin Assignment

Pin Assignment

90 Pins 90 Pins

90 Connections

90 Pins 90 Pins

Assign all nets to unique pin locations

− such that overall design performance is optimized.

− Criteria: routability, electrical parasitics, …

Best locations depend on the relative placement of the blocks.

Each pin on the microprocessor must be connected to an IO pin at the next hierarchy level.

Basic Concepts

3

Electrically-Equivalent Pins: (connected)

Functionally-Equivalent Pins: (functionality of circuit not change if swapped)

Contact

Metal1

polysilicon

p/n diffusion

Via

Metal2

Pin Assignment: Example

4

Pin Assignment Algorithm

• Pin assignment by concentric circles:• Objective:

Establish connections between a block and its related pins in other blocks

• Criterion: Minimize net crossings

• Assumption: All outer pins (pins outside of the current block) have

fixed locations.• Goal:

Assign locations to all inner pins (pins in the current block) based on the locations of the electrically-equivalent outer pins.

5

6

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

Given: Two sets of pins (1 )Determine the circles

Pin Assignment – Example

7

(2 )Determine the points

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

8

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

(2 )Determine the points

9

(3 )Determine initial mapping (arbitrarily)

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

10

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

(3 )Determine initial mapping and (4) optimize the mapping (complete rotation)

11

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

(3 )Determine initial mapping and (4) optimize the mapping (complete rotation)

12

(4 )Best mapping (shortest Euclidean distance)

Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

13

Final pin assignment

3.6 Pin Assignment – Example

Kor

en, N

. L.:

Pin

Ass

ign

men

t in

Au

tom

ated

Pri

nted

Cir

cuit

Boa

rds

(4 )Best mapping