ISD5116
Starting at the MICROPHONE inputs, the signal from the microphone can be routed directly through
the chip to the ANA OUT pins through a 6 dB amplifier stage (Feed Through Mode). Or, the signal
can be passed through the AGC amplifier and directed to the ANA OUT pins, directed to the storage
array, or mixed with voice from the receive path coming from ANA IN and be directed to the same
places.
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. Under this situation, the other party's voice from the phone is
played into ANA IN and passed through to the AUX OUT pin that drives the car kit's loudspeaker.
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 anti-aliasing)
and into the storage array. Later, the cell phone owner can playback 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
configurations, providing greater flexibility.
7.2.1. Internal Registers
The ISD5116 has multiple internal registers that are used to store the address information and the
configuration or set-up of the device. The two 16-bit configuration registers control the audio paths
through the device, the sample frequency, the various gains and attenuations, power up and down of
different sections, and the volume settings. These registers are discussed in detail in section 7.3.5 on
page 20.
7.2.2. Memory Organization
The ISD5116 memory array is arranged as 2048 pages (or rows) of 2048 bits for a total memory of
4,194,304 bits. The primary addressing for the 2048 pages is handled by 11 bits of address input in
the analog mode. At the 8 kHz sample rate, each page contains 256 milliseconds of audio. Thus at 8
kHz there is actually room for 8 minutes and 44 seconds of audio.
A memory page is 2048 bits organized as thirty-two 64-bit "blocks" when used for digital storage. The
contents of a page are either analog or digital. This is determined by instruction (op code) at the time
the data is written. A record of where is analog and where is digital, is stored in a message address
table (MAT) by the system microcontroller. The MAT is a table kept in the microcontroller memory that
defines the status of each message “page”. It can be stored back into the ISD5116 if the power fails or
the system is turned off. Using this table allows for efficient message management. Segments of
messages can be stored wherever there is available space in the memory array. [This is explained in
detail for the ISD5008 in Applications Note #9 and will be similarly described in a later Note for the
ISD5116.]
Publication Release Date: August, 2002
- 11 - Revision 2.0