The device has dedicated clock pins. Some peripherals, such as SPI, TWI, and TRACE, have clock signals.
The dedicated clock pins are optimized to ensure correct timing between the clock and data signals for these peripherals. All peripherals that have clock signals must use these pins. See Pin assignments for the full list.
The data signal associated with the peripheral must use pins close to the clock pin. This ensures that the internal paths from the peripheral to the pin have the same delay, so that the data and clock signals reach the pins at the same time.
For high-speed signals, the printed circuit board (PCB) layout must use short PCB traces of identical length. This reduces delays and ensures the same delay on the clock and data path.