What is follow pin in VLSI physical design?

 In VLSI physical design, a follow pin is a special type of pin used to specify the routing direction of a net or signal. The follow pin is used to guide the routing of a net, making sure that it follows a specific direction or path.

Follow pins are often used in high-speed digital circuits, where the routing of signals can significantly affect the performance of the circuit. Designers may ensure that the signal takes the best path by setting the routing direction of a net using a follow pin, lowering the chance of crosstalk and other problems. It often sits at the start or end of a net and specifies which way the signal should be sent. The signal is then routed along the designated path using the pins attached to the net, ensuring that it travels in the intended direction. To further boost the performance of the circuit, follow pins can be utilised in conjunction with other routing strategies like wire spacing and shielding. In summary, a follow pin is a special type of pin used in VLSI physical design to specify the routing direction of a net or signal. It is used to guide the routing of a net, ensuring that the signal follows the optimal path and reducing the risk of crosstalk and other issues. Follow pins are particularly useful in high-speed digital circuits, where signal routing can significantly affect circuit performance.