Feed Through Path

For a complete SoC design, the entire SoC is further divided into Blocks that have a particular functionality, and those functionalities are already defined. These blocks are interconnected to each other on the SoC.

But, there can be some scenarios when the interacting blocks cannot be placed close to each other, then to connect them Feed-Through paths are introduced in the design which helps in data transfer and also it helps in synchronizing of those data transfers. So, the use of Feed-Through paths in a design is to connect those blocks which are placed far away from each other on the SoC.

For example, Refer to Fig.1  There are 10 blocks in the design. Now, suppose the output of block 4 is to be connected to the input of block 6, it can be done in two ways as below:

  • Outside routing from the output port of block 4 directly to the input of block 6.
  • The data transfer takes place via Block 5 – So, Block 5 is Feed-Through block and Input port of Block 5 is Feed-Through input port and output port of block 5 is Feed-Through output port.

Fig. 1: Feed Through Path

Advantages of Feed-Through Path

  • Reduce routing resources on chip which helps in reducing congestion.
  • Power Optimization.
  • Area Optimization.

Problems in introducing Feed-Through Path

  • If there are a number of Feed-Through paths then It can create congestion near the Feed-Through ports.
  • In a case when data cannot reach the destination point within the required clock time, the addition of pipeline registers may be required.

So, before introducing the Feed-Through path in the design various aspects like operating frequency, area utilization congestion analysis, etc needs to be taken care of. 

One solution to fix congestion near the Feed-Through port is the Swapping technique. In the swapping technique, the various Feed-Through ports present in the design are swapped to fix congestion near the port. But, if the particular port of a Block is interacting with other blocks, then swapping needs to be done while taking care of other blocks also.

So from this blog, you can answer the below set of questions:

  • What is Feed-Through Path?
  • What problems can occur in introducing Feed-Through Path?
  • Suggest a technique to fix congestion near the Feed-Through Port.  
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