Routing

Routing definitions : 1. Pin – input or output of the logical circuit; 2. Connection – a pair of contacts that have been connected

with each other; 3. Net – a number of logical circuit contacts that must be

connected with each other. Is divided into connections; 4. Wire Segment – part of wire that is used as part of the

connection; 5. Routing Switch – programmable switch that is used to

connect segments; 6. Track – conductor that passes throughout the routing

channel. Consists of several segments; 7. Routing Channel – number of tracks between the logical

circuits.

LB LB

LBLB

Pin

Track

Switch

Channel

Segment

LB

LB

Conflicts in routing

LB

LB

123

LB

LB

LB

LB

123

LB

LB

LB

LB

123

A

B

C

Routing strategy

Routing resources are divided into routing areas. Global Router makes each connection correspond to one

routing area. o Divides the connections of several contacts into

single connections. o Each single sonnection is made to correspond to

some certain channel. Detailed Router realises connections within the

respective areas. o Makes each connection to correspond with a wire

segment that enables its realisation

Routing is NP – Complete

Row-based

LB

LB LB

LB

LB

LBLB

LB LB

LB

LB LB LBLB LB

LB LB

LBLB

Row Based arcitecture

c1 c2

c3c4

c1c1 c2c2 c3 c3 c4c4

c1c1 c2c2 c3 c3 c4c4

Mask programmable array

Not segmented

c1c1 c2c2 c3 c3 c4c4

Routing in row-based FPGA

Totally segmented

2-segment routing

c1c1 c2c2 c3 c3 c4c4

1-segment routing

c1c1 c2c2 c3 c3 c4c4

Routing with segmentation

c1 c2

c3c4

1 2 3 4 6 7 8 9 105

1

2

3

c1

c2

c3

c4c5

x0

6,7,1

6,1,11,5

2,9

On which track is the connection realised

How many segments it takes to realise theconnections (accumulative)

Which is the first freevertical on the first, secondand third track routing in givenstep

Parameters used in routing

Example of routing

Track

1 2 3 4 6 7 8 9 105

1

2

3

c1

c2

c3

c4c5

x0

N,N,7

N,6,N

N,7,N

6,1,7

1,6,7

1,7,7

6,7,1

N,6,7

N,7,7

N,N,N6,1,1

1,6,1

1,1,7

1,5

2,9

3,17

3,8

2,5

3,4

2,11

3,81

1

2,8

1,16

1,15 3,20

3,19

3,20

2,19

3,20

2,21

N,N,N

6,7,N 6,N,N2,20

N,N,N1,21

N,7,N1,21

N,N,N2,22

N,N,N

N,N,7

2,18

2,21N,N,N

Finally 21

Finally 21 ja 22

Finally 22 ja 23

Track

1 2 3 4 6 7 8 9 105

1

2

3

c1

c2

c3

c4c5

Solution

This routing used the least number of segments (19)The smallest number of switches is on the track and it is the fastest.

Track

1 2 3 4 6 7 8 9 105

1

2

3

c1

c2

c3

c4c5

x0 1,N,9 N,N,91,1,93,5 2,9 1,17 Routing is not

possible

Diminishing the number of switches may disable routing.

Switches removed

Densityof thechannel

50%

100%

Possibility of routing

The location of plunge depends onthe segmentationof the channel.

LB

LB LB

LB

LB

LB

LB LB LB

Interconnection resourcees

LB

LB

LB

LB

CLK

SBCB CB

CB

CB

Connection arrays

Long lines

Connectionsbetweenneighbours

Symmetrical Array

Lengths of connections

01234

01234 0 1 2 3 4

0 1 2 3 4 01234

01234 0 1 2 3 4

0 1 2 3 4

01234

01234 0 1 2 3 4

0 1 2 3 4 01234

01234 0 1 2 3 4

0 1 2 3 4

1 0

1 0

1 0

1 0

2

3

4

3

3 3

2 4

2 4

2 4

Global router

L C L

C S C

L C L0

1

2

0 1 2L

C

S

C

L

0,0

0,1

1,1

2,1

2,2

Detailed router

L

C

S

C

L

0,0

0,1

1,1

2,1

2,2

L L

C C

L L0

1

2

0 1 2

C

S

C

0 1 2

L

C

SSS

CCCC

CCCC

Cost Function

LB

LB

LB

LB

123

LB

LB

LB

LB

123

LB

LB

LB

LB

123

3

2

1

Shows the number of possibilities left for realising the connection at any stage of routing.

Problems :1. What is the effect of CB on routing.2. What is the effect of SB on routing.3. How are the possibilities of SB and CB connected with routing.4. How are the possibilities of SB and CB connected with

the number of lines necessary for 100% routing5. How are the possibilities of SB and CB connected with the sum

number of keys that would guarantee 100% routing.

Fs=6

Switch Block (SB)

Connection Block (CB)

LB LB

Fc=2

SB and CB architectures