Audio signal encoding circuit integrated into the CPU

With the development of MP3/MP4 machine integration, most of the audio signal encoding circuits are integrated into the CPU and decoder chips (as
shown in the figure), which greatly simplifies the overall circuit of the MP3 machine. In circle 28-11, the @ and @ pins of ACU7505 input microphone signals, the @ and
(D pins input line input signals, and the @ and @ pins input FM radio signals. These signals are A/D converted and digitally
encoded , convert the analog audio signal into a digital audio signal and store it in the memory. Complete the recording process of the audio signal .