In typical SPI systems with one master and multiple slaves, a dedicated chip-select signal is used to address an individual slave. As the number of slaves increase, so do the number of chip-select lines. In this situation, the board layout of the system can become quite a challenge. One layout alternative is daisy-chaining. This application note explains the details of a daisy-chained SPI system and shows how software can be used to propagate commands through a string of slaves.