Described in this slide are the operating modes found in low power systems. It becomes difficult when comparing MCUs from different vendors because of the different naming conventions for the different low power modes, and not all of the modes behave the same way. Silicon Labs defines when the CPU is performing calculations or making decisions as the active mode; all clocks are active and the CPU is fetching and executing instructions from flash memory. More bandwidth and low frequency sensitivity are key parameters in the overall average power consumption. The MCU is considered to be in an idle mode when the CPU is not executing instructions, but all other peripherals remain active. This is useful when it is necessary to use a peripheral that requires the clock system of the MCU, such as transferring some data from the UART. The clock frequency can be reduced to the minimum value and wait for the transfer to be completed. The idle mode has many different names across different vendors, it is important to compare the data sheets to see the equivalent modes.