LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
System description
Page 28 of 103
Figure 11: Other URC transmissions
1.9.2.2
UART and power saving
During the idle mode, the device turns off non-vital functions to take advantage of the power consumption
improvements, and during this time, a 32 KHz clock runs to synchronize all the tasks needed. CDMA states that
a device should awake at the designated slotted time given by the System_Parameters_Message using the
max_slot_cycle_index value assigned by the network. During this moment, all RF components of the terminal will
start running to decode all the messages coming in via the paging channel, will respond accordingly, and will go
back to idle mode once the active mode period ends, if no action is requested.
If during the idle mode, the host application sends any interaction data to the device, it will process this
information and will respond accordingly; the latency time for the wake-up action is about 20 ms.
UART power saving is implemented in versions C200-02S-01 and C200-22S-01, and onwards.
In comparison to USB, the UART power saving implementation presents a better power consumption for
this purpose.
By default, the power saving mode is disabled. In order to force the module to enter power saving mode:
•
AT command AT+UPSV=4 must be issued
•
Host must keep low the TxD pin (pin 15 on LISA-C200, pin 32 in FW75-C200)
Once the TxD pin has been put low by the host, the UART is disabled. The host must monitor the RI line in order
to trigger a system wake up (by releasing the TxD line) in case of network notifications.
•
AT+UPSV command is saved in the non-volatile memory.
•
If power saving is enabled (+UPSV=1), the UART interface is cyclically enabled and the module enters power
save mode once the timeout value is completed.
•
If the power saving mode is controlled by the UART RTS signal (+UPSV=2), the UART interface is enabled
and the module doesn’t enter power save mode as long as the RTS line is ON.
•
AT+UPSV=4 command must be issued before putting low the TxD pin to ensure proper power saving
operation.
•
If power saving mode is disabled (+UPSV=0), the UART interface is always enabled and the module doesn’t
enter power save mode.
•
The current consumption profiles when power saving is enabled and disabled are shown in the figures
below.
0
RI
1s
URC
1
time [s]
