Starting at the MICROPHONE inputs, the input signal at the MICROPHONE inputs can be routed in
the following ways:
• directly through the Voice band CODEC of the I5216 chip, then through the SDIO pin, to output
the digital PCM signal.
• through the AGC amplifier, before it is routed to the voice band CODEC.
• through the AGC amplifier to the storage array
• through the AGC amplifier and mixed with an analog voice band CODEC signal coming from
the digital SDI pin
In addition, if the phone is inserted into a "hands-free" car kit, then the signal from the pickup
microphone in the car can be passed through to the same places from the AUX IN pin and the phone's
microphone is switched off. In this scenario, the other party's voice from the phone would be played
into the PCM IN input and passed through to the AUX OUT pin that would drive the car kit's
Depending upon whether one desires recording one side (simplex) or both sides (duplex) of a
conversation, the various paths will also be switched through to the low pass filter (for antialiasing) and
into the storage array. Later, the cell phone owner can play back the messages from the array. When
this happens, the Array Output MUX is connected to the volume control, through the Output MUX, to
the Speaker Amplifier. For applications other than a cell phone, the audio paths can be switched into
many different and flexible configurations. Some examples follow.
Publication Release Date: November 30, 2001