LISA-U2 series - System integration manual
UBX-13001118 - R27
System description
Page 81 of 183
C1-Public
1.9.4.2
IPC communication and power saving
If power saving is enabled by an AT command (AT+UPSV=1, AT+UPSV=2 or AT+UPSV=3), the LISA-
U2 module automatically enters idle mode whenever possible, if the host indicates that it is not ready
to transmit or receive by the
SPI_MRDY
signal, or if the LISA-U2 series module itself does not transfer
data.
1.9.4.3
IPC communication examples
In the following, three IPC communication scenarios are described:
•
Local device-initiated data transfer, with a sleeping host
•
host-initiated data transfer, with a sleeping local device
•
Local device-ended data transfer
Local device-initiated transfer with a sleeping host
Figure 42: Data transfer initiated by the LISA-U2 module (local device), with a sleeping application processor (host)
When the host is sleeping (idle mode), the following actions happen:
1.
The local device indicates to the host that is ready to send data by activating
SPI_SRDY
.
2.
When the host becomes ready to send, it signalizes this by activating
SPI_MRDY
.
3.
The host activates the clock and the two processors exchange the communication header and
data.
4.
If the data has been exchanged, the local device deactivates
SPI_SRDY
to process the received
information. The host does not need to de-assert
SPI_MRDY
as it controls the
SPI_SCLK
.
5.
After the preparation, the local device activates
SPI_SRDY
again and waits for
SPI_SCLK
activation. When the clock is active, all the data is transferred without intervention. If there is
more data to transfer (flag set in any of the headers), the process will repeat from step 3.
SPI_MRDY
SPI_SRDY
DATA EXCHG
2
4
5
Header
Data
Header
3
1