Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 System description Page 36 of 119
1.13.9.2 Functionality
When power saving is enabled using the AT+CPSMS command, the module automatically enters the low power deep
sleep mode whenever possible, reducing current consumption (see the section 1.5.1.4 and the SARA-R4/N4 series Data
Sheet [1]).
For the definition and the description of the SARA-R4/N4 series operating modes, including the events forcing transitions
between the different operating modes, see section 1.4.
The SARA-R4/N4 series modules achieve the low power deep sleep mode by powering down all the Hardware
components with the exception of the 32 kHz reference internally generated.
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☞ From the host application point of view, the serial port will not be available during low power deep sleep mode, as
the SARA-R4/N4 series module will act as if it is in Power-Off mode.
1.13.9.3 Timers and network interaction
The SARA-R4/N4 series modules goes in low power deep sleep mode entering in the Power Saving Mode (PSM) defined
in 3GPP Release 13.
Two timers have been specified on the PSM Signaling: the “Periodic Update Timer” and “Active Timer”.
The “Active Timer” is the time defined by the network where the SARA-R4/N4 series module will keep listening for any
active operation, during this time the module is in Active mode.
The “Periodic Update Timer” is the Extended Tracking Area Update (TAU) used by the SARA-R4/N4 series module to
periodically notify the network of its availability.
The SARA-R4/N4 series module requests the PSM by including the “Active Timer” with the desired value in the Attach,
TAU or Routing Area Update (RAU) messages. The “Active Timer” is the time the module listens to the Paging Channel
after having transitioned from connected to active mode. When the “Active Timer” expires, the module enters PSM low
power deep sleep mode.
SARA-R4/N4 series module can also request an extended “Periodic Update Timer” value to remain in PSM low power
deep sleep mode for longer than the original “Periodic Update Timer” broadcasted by the network.
The grant of PSM is a negotiation between SARA-R4/N4 series module and the attached network: the network accepts
PSM by providing the actual value of the “Active Timer” (and “Periodic Update Timer”) to be used in the Attach/TAU/RAU
accept procedure. The maximum duration, including the “Periodic Update Timer”, is about 413 days. The SARA-R4/N4
series module enters PSM low power deep sleep mode only after the “Active Timer” expires.
PSM low power deep sleep mode
(periodic update timer)
Connected mode: Data Tx / Rx
Active mode
(active timer)
Time
Current
Figure 14: Description of the PSM timing
1.13.9.4 Timers and AT interaction
The SARA-R4/N4 series modules go into low power deep sleep mode and enter the Power Saving Mode (PSM) only after
the 6 s “AT Inactivity Timer” expires:
• If the UART interface is used, when the host application stops sending AT commands for 6 s – the “AT Inactivity Timer”
expiration – then the module enters deep sleep power saving mode according to “Active Timer” expiration.