LE910Cx Hardware Design Guide
1VV0301298 Rev.40 Page 74 of 149 2023-03-16
Not Subject to NDA
8.4.2. Modem Serial Port 2
On the LE910Cx, Serial Port 2 is a +1.8V UART with Rx and Tx signals only.
The UART functionality is shared with SPI, thus simultaneous use of SPI and UART is not
supported.
Table 29 lists the signals of the LE910Cx Serial Port 2.
PAD Signal I/O Function Type Comment
D15 TXD_AUX O Auxiliary UART
(Tx Data to DTE)
1.8V Shared with
SPI_MOSI
E15 RXD_AUX I Auxiliary UART
(Rx Data to DTE)
1.8V Shared with
SPI_MISO
Table 29: Modem Serial Port 2 Signals
Note:
According to V.24, Rx/Tx signal names refer to the application
side; therefore, on the LE910Cx side, these signal are in the opposite
direction: TXD on the application side will be connected to the receive
line (here named TXD/ RX_UART) of the LE910Cx serial port and vice
versa for Rx.
Note:
The DTR pin is used to control the UART and system sleep
Pulling the DTR pin down prevents the UART and the entire module
from entering low power mode.
DTR can be left floating if not used (DTR is internally pulled high).
Note:
To avoid a back-powering effect, it is recommended to prevent
any HIGH logic level signal from being applied to the module’s digital
pins when it is powered OFF or during an ON/OFF transition.
Note:
The Auxiliary UART is used as the SW main debug console. It
is required to place test points on this interface even if not used.
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