PCF8591 has one 8 bit ADC on board for 4 channels. The ADC is 8 bit and quite fast. At 100 KHz one gets more than 2000 reads per second for read() and more than 2000 writes per second for write().

Arduino support for STC8 microcontrollers with a familiar Arduino-like API. Note: P3_2 and P3_3 can using FALLING, RISING or CHANGE modes, while other pins only support FALLING mode.