Flash memory file system in a handheld record and playback device
United States Patent 5839108
Overall system design is based on the use of a microprocessor which can drive all system components. This eliminates the need for use of multiple interface logic that demands a lot of board space within the circuitry. The DSP or digital support processor is coupled to the microprocessor and to a CODEC for coding and decoding the analog signal received from the microphone or transmitted to the speaker. Codec also performs the analog to digital conversion. It functions to receive the analog signal input and convert it to PCM or pulse code modulation and then feed this signal to the DSP. Conversely, when operating in play back mode, the DSP will feed pulse code modulation digital signal to the codec and the codec converts it to an analog signal that can be fed through an amplifier to a speaker.
