Efficiency is another feature that is provided with the use of R8C Family MCUs. These devices consume much less power than other 8-bit solutions because they incorporate multiple techniques for improving system power efficiency. Consider the internal clock circuitry, for instance. There are at least four different clock sources: two on-chip oscillators (low-speed and high-speed), the external main system clock (XIN), and the 32kHz subclock (XCIN). With this design, the CPU can run as fast as 20MHz or as slow as a pre-scaled 32kHz, depending on the needs of the application. Also, different clock sources and speeds can be selected for each peripheral module, independent of the CPU clock, to optimize power consumption. Peripherals can even be turned off to save more power when they are not needed. Furthermore, when the A/D converter isn't being used, additional power can be saved. Software can turn off the circuit that generates the converter's reference voltage, thereby eliminating current flow from the reference voltage to the register ladder. Power-down modes are another technique for reducing power consumption. R8C Family MCUs have three main operating modes: Normal, Wait, and Stop. In Normal mode (sometimes also called Active mode), the device is fully operational. However, the main clock can be divided down by 1, 2, 4, 8, 16 or 32 so that the CPU core and peripherals can run at less than full speed to conserve power. In Wait mode, the CPU is turned off but all peripherals can operate from any of the available clock sources. Power consumption can be reduced by over 99 percent compared to the Normal mode. In Stop mode, the CPU and peripherals can be put into a deep-standby condition, reducing power consumption to an absolute minimum.