LISA-U2 series - System integration manual
UBX-13001118 - R27
System description
Page 83 of 183
C1-Public
1.9.4.4
IPC application circuits
SPI_MOSI
is the data line input for the module since it runs as an SPI local device: it must be connected
to the data line output (MOSI) of the application processor that runs as an SPI host.
SPI_MISO
is the data line output for the module since it runs as an SPI local device: it must be
connected to the data line input (MISO) of the application processor that runs as an SPI host.
SPI_SCLK
is the clock input for the module since it runs as an SPI local device : it must be connected
to the clock line output (SCLK) of the application processor that runs as an SPI host.
SPI_MRDY
is an input for the module able to detect an external interrupt which comes from the SPI
host: it must be connected to a GPIO of the application processor that runs as an SPI host.
SPI_SRDY
is an output for the module that must be connected to a pin of the application processor
that runs as an SPI host able to detect an external interrupt which comes from the module.
Signal integrity of the high speed data lines may be degraded if the PCB layout is not optimal,
especially when the SPI lines are very long: keep routing short and minimize parasitic capacitance to
preserve signal integrity. It is recommended to match the length of SPI signals.
If a 1.8 V application processor is used, the SPI host pins can be directly connected to the specific
LISA-U2 SPI local device pins as described in
. It is recommended to tri-state the output pins
of the SPI host (i.e. set in high impedance mode) when the LISA-U2 module is in power-down mode,
when the external reset is forced low, and during the module power-on sequence (at least for 3
seconds after the start-up event), to avoid latch-up of circuits and allow a clean boot of the module.
MOSI
Application processor
(1.8V SPI master)
MISO
SCLK
Interrupt
GND
LISA-U2 series
(1.8V SPI slave)
56
SPI_MOSI
59
SPI_MRDY
57
SPI_MISO
55
SPI_SCLK
58
SPI_SRDY
GND
GPIO
Figure 45: IPC / SPI Interface application circuit connecting LISA-U2 series 1.8V SPI local device to a 1.8V SPI host
