LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 91 of 175
When I
2
S word alignment toggles high, the first synchronization bit is always low. Second synchronization
bit (present only in case of 2 bit long I
2
S word alignment configuration) is MSB of the transmitted word (MSB
is transmitted twice in this case)
I
2
S transmit data changes on I
2
S clock rising edge, I
2
S receive data changes on I
2
S clock falling edge
1.11.2
I
2
S interface - Normal I
2
S mode
Normal I
2
S supports:
16 bits word
Mono interface
Configurable sample rate: 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48 kHz
Main features of I
2
S interface in normal I
2
S mode:
I
2
S word alignment signal always runs at <sample_rate> and synchronizes 2 channels (timeslots on word
alignment high, word alignment low)
I
2
S transmit data is composed of 16 bit words, dual mono (the words are written on both channels). Data
are in 2’s complement notation. MSB is transmitted first. The bits are written on I
2
S clock rising or falling
edge (configurable)
I
2
S receive data is read as 16 bit words, mono (words are read only on the timeslot with WA high). Data is
read in 2’s complement notation. MSB is read first. The bits are read on the I
2
S clock edge opposite to I
2
S
transmit data writing edge (configurable)
I
2
S clock frequency is 16 bits x 2 channels x <sample_rate>
The modes are configurable through a specific AT command (see the
[2], +UI2S
AT command) and the following parameters can be set:
MSB can be 1 bit delayed or non-delayed on I
2
S word alignment edge
I
2
S transmit data can change on rising or falling edge of I
2
S clock signal (rising edge in this example)
I
2
S receive data are read on the opposite front of I
2
S clock signal
1.11.3
I
2
S interface application circuits
LISA-U2 I
2
S digital audio interfaces can be connected to an external digital audio device for voice applications.
Any external digital audio device compliant to the configuration of the digital audio interface of the cellular
module can be used, given that the external digital audio device has to provide:
The opposite role: slave or master for LISA-U2 modules that may act as master or slave
The same mode and frame format: PCM / short alignment or Normal I
2
S mode / long alignment mode with
o
data in 2’s complement notation
o
MSB transmitted first
o
word length = 16-bit
o
frame length = 17-bit or 18-bit in PCM / short alignment mode (16 + 1 or 16 + 2 clock cycles, with
Word Aligment / Synchronization signal set high for 1 clock cycle or 2 clock cycles), or
o
frame length = 32-bit in Normal I
2
S mode / long alignment mode (16 x 2 clock cycles)
The same sample rate and serial clock frequency: as the clock frequency depends on the frame length and
the sample rate, the clock frequency can be
o
17 x <I2S_sample_rate> or 18 x <I2S_sample_rate> in PCM / short alignment mode, or
o
16 x 2 x <I2S_sample_rate> in Normal I
2
S mode / long alignment mode
Compatible voltage levels (1.80 V typ.), otherwise it is recommended to connect the 1.8 V digital audio
interface of the module to the external 3.0 V (or similar) digital audio device by means of appropriate
