Freescale Semiconductor MPC5604B, Quick Start Manual

Page: 73 / 150

Figure 85 : A time diagram of different signals involved in SPI, depending on CPOL/CPHA
When using SPI with multiple slaves there are different possibilities for connecting them. If the
master has enough chip select signals, then each slave can be independent and communicate
with the master only when asked. But in the case where the master has only one chip select
signal, then a configuration called daisy-chained SPI can be used. In this chain, each device sends
its data to the next device and receives from the previous one. This can slow down the
communication between far ends of the chain but it also enables slaves to communicate among
each other without needing to go through the master. (Even though this requires some kind of
identification method to be defined.)
Figure 86 : SPI Configurations: Independent(left) \ Daisy-chained (right)