u-blox LARA-R203 System Integration Manual page 47

Wake-up via data reception
The UART wake-up via data reception consists of a special configuration of the module TXD input line that causes
the system wake-up when a low-to-high transition occurs on the TXD input line. In particular, the UART is enabled
and the module switches from the low power idle mode to active mode within ~20 ms from the first character
received: this is the system "wake-up time".
As a consequence, the first character sent by the DTE when the UART is disabled (i.e. the wake up character) is
not a valid communication character, even if the wake up via data reception configuration is active, because it
cannot be recognized, and the recognition of the subsequent characters is guaranteed only after the complete
system wake-up (i.e. after ~20 ms).
The UART wake-up via data reception configuration is active in the following cases:

AT+UPSV=1 is set with HW flow control disabled
Figure 22 and Figure 23 show examples of common scenarios and timing constraints:

AT+UPSV=1 power saving configuration is active and the timeout from last data received to idle mode start is
set to 2000 frames (AT+UPSV=1,2000)

Hardware flow control is disabled
Figure 22 shows the case where the UART module is disabled and only a wake-up is forced. In this scenario, the
only character sent by the DTE is the wake-up character; as a consequence, the DCE module UART is disabled
when the timeout from last data received expires (2000 frames without data reception, as the default case).
UART
OFF
ON
TXD input
OFF
ON
Wake up character
Not recognized by DCE
Figure 22: Wake-up via data reception without further communication
Figure 23 shows the case where in addition to the wake-up character, further (valid) characters are sent. The wake-
up character wakes up the UART module. The other characters must be sent after the "wake up time" of ~20 ms.
If this condition is satisfied, the module (DCE) recognizes characters. The module will disable the UART after 2000
GSM frames from the latest data reception.
UART
OFF
ON
TXD input
OFF
ON
Wake up character
Not recognized by DCE
Figure 23: Wake-up via data reception with further communication
UBX-16010573 - R12
DCE UART is enabled for 2000 GSM frames (~9.2 s)
Wake up time: ~20 ms
DCE UART is enabled for 2000 GSM frames (~9.2s)
after the last data received
Wake up time: ~20 ms
Valid characters
Recognized by DCE
LARA-R2 series - System Integration Manual
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System description
Page 47 of 157