SARA-G3 series - System Integration Manual
UBX-13000995 - R06
Objective Specification
System description
Page 69 of 218
1.10.2.1
I
2
S interface – PCM mode
Main features of the I
2
S interface in PCM mode:
I
2
S runs in PCM – short alignment mode (configurable by AT commands)
I
2
S word alignment signal is configured to 8 kHz: this is the <sample_rate> parameter
I
2
S word alignment toggles high for 1 or 2 CLK cycles of synchronization (configurable), then toggles
low for 16 CLK cycles of sample width. Frame length can be 1 + 16 = 17 bits or 2 + 16 = 18 bits
I
2
S clock frequency depends on frame length and the 8 kHz sample rate. Can be 17 x 8 kHz or 18
x 8 kHz
I
2
S transmit and I
2
S receive data are 16 bit words long with the same sampling rate as I
2
S word
alignment, mono. Data is in 2’s complement notation. MSB is transmitted first
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
1.10.2.2
I
2
S interface – Normal I
2
S mode
Normal I
2
S supports:
16 bits word
Mono interface
Sample rate: 8 kHz
Main features of I
2
S interface in normal I
2
S mode:
I
2
S runs in normal I
2
S – long alignment mode (configurable by AT commands)
I
2
S word alignment signal always runs at 8 kHz 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 8 kHz
The modes are configurable through a specific AT command (refer to the related section in the
u-blox
AT Commands Manual [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
I
2
S receive data are read on the opposite front of I
2
S clock signal
