A typical SoC consists of:
one or more microcontroller, microprocessor or DSP core(s)
memory blocks including a selection of ROM, RAM, EEPROM and Flash
Timing sources including oscillators and phase-locked loops
Peripherals including counter-timers, real-time timers and power-on reset generators
External interfaces including industry standards such as USB, FireWire, Ethernet, USART, SPI
Analog interfaces including ADCs and DACs
Voltage regulators and power management circuits
System on chip can be composed by using microcontrollers..
Rgards..
Sujith