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Writer's picturedeepansh arora

What is PNR

**Place and route** is a critical step in the physical design process of a System on Chip (SoC) after the synthesis stage. It involves determining the physical layout of the components on the chip and establishing the connections (routing) between them. Here’s a detailed breakdown of the place and route process:


### Key Steps in Place and Route


1. **Placement**:

- **Definition**: This step involves positioning the various components (gates, flip-flops, memory blocks, etc.) within a predefined area on the chip.

- **Objectives**:

- Minimize the area used by the components.

- Optimize for performance (reduce signal delay).

- Reduce power consumption (shorter connections often result in lower power usage).

- Improve manufacturability and yield.


2. **Routing**:

- **Definition**: After placement, routing establishes the connections between the placed components using metal layers that form the wiring paths.

- **Objectives**:

- Ensure that all connections are made according to the design specifications.

- Avoid signal interference and congestion.

- Minimize the overall wire length to enhance performance and reduce power.


3. **Timing Closure**:

- This involves verifying that the design meets all timing constraints after placement and routing. Static timing analysis is performed to ensure that signal propagation delays do not violate setup and hold times.


4. **Physical Verification**:

- After place and route, the design undergoes physical verification to check for any layout issues, such as design rule violations (DRC), electrical rule checks (ERC), and connectivity checks.


5. **Optimization**:

- Further optimization may be performed to improve performance, reduce power, or minimize area after initial placement and routing. This can involve iterating back through placement and routing steps.


### Importance of Place and Route


- **Performance**: The efficiency of the placement and routing directly affects the speed and performance of the final SoC.

- **Power Consumption**: Effective routing and placement can significantly reduce power consumption, which is critical in battery-operated devices.

- **Area Utilization**: Optimizing the layout can help reduce the physical size of the chip, lowering manufacturing costs.

- **Manufacturability**: A well-designed layout ensures better yield and reliability during the fabrication process.


### Tools


Common EDA tools for place and route include:


- **Cadence Innovus**

- **Synopsys IC Compiler**

- **Mentor Graphics Olympus-SoC**


In summary, place and route is a fundamental process in SoC design that transforms the logical representation of a circuit into a physical layout, ensuring that the final design meets performance, power, and area specifications while being manufacturable.

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