ISD5100 – SERIES
The command sequence for an Analog Record would be a four byte sequence consisting of the Slave
Address (80h), the Command Byte (91h) for Record Analog @ Address, and the two address bytes.
See “Load Command Byte Register (Address Load)” in section 7.3.2 on page 17.
7.3.7. Feed Through Mode
The previous examples were dependent upon the device already being powered up and the various
paths being set through the device for the desired operation. To set up the device for the various
paths requires loading the two 16-bit Configuration Registers with the correct data. For example, in
the Feed Through Mode the device only needs to be powered up and a few paths selected.
This mode enables the ISD5100 Series to connect to a cellular or cordless base band phone chip set
without affecting the audio source or destination. There are two paths involved, the transmit path and
the receive path. The transmit path connects the Winbond chip’s microphone source through to the
microphone input on the base band chip set. The receive path connects the base band chip set’s
speaker output through to the speaker driver on the Winbond chip. This allows the Winbond chip to
substitute for those functions and incidentally gain access to the audio to and from the base band chip
To set up the environment described above, a series of commands need to be sent to the ISD5100-
Series. First, the chip needs to be powered up as described in this section. Then the Configuration
Registers must be filled with the specific data to connect the paths desired. In the case of the Feed
Through Mode, most of the chip can remain powered down. The following figure illustrates the
ANA IN AMP
The figure above shows the part of the ISD5100 Series block diagram that is used in Feed Through
Mode. The rest of the chip will be powered down to conserve power. The bold lines highlight the audio
paths. Note that the Microphone to ANA OUT +/– path is differential.
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