User's Manual

SARA-R4 series - System Integration Manual
UBX-16029218 - R03 System description
Page 29 of 94
The “Periodic Update Timer” is the Extended Tracking Area Update (TAU) used by the SARA-R4 series module to
periodically notify the network of its availability.
The SARA-R4 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 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 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 “Periodic Update Timer”, is about 413
days. The SARA-R4 series module enters PSM low power deep sleep mode only after “Active Timer” expires.
PSM low power deep sleep mode
(periodic update timer)
Connected mode: Data Tx / Rx
Active mode
(active timer)
Time
Current
Figure 9: Description of the PSM timing
1.12.9.3 AT Commands
The module uses the +CPSMS AT command with its defined parameters to request PSM timers to the network.
See the SARA-R4 series AT Commands Manual [2] for details of the +CPSMS operation and features.
1.12.9.4 Host Application
The PSM low power deep sleep mode implementation allows the SARA-R4 series module to help extend the
battery life of the application.
The Host Application should be aware the SARA-R4 series module is PSM capable.
The host application needs to configure any available GPIO by means of AT commands (refer to GPIO
section of SARA-R4 series AT Commands Manual [2]) to get the notification when the module has
entered into PSM low power deep sleep mode.
If the host application receives an event that needs to be reported by the SARA-R4 series module
interrupting the PSM low power deep sleep mode, it can be done so by setting the module into Active
mode using the appropriate power-on event (see 1.6.1).
From the host application point of view, the SARA-R4 module will look as it is in Power-Off mode.
1.12.9.5 Normal Operation
The Host Application can force the SARA-R4 series module to transition from PSM low power deep sleep mode
to Active mode by using the Power Up procedure specified in section 1.6.1.
Host application should be aware that transitioning from low power deep sleep mode to active mode will
make the SARA-R4 series module to consume same amount of power as in Active-Mode shortening the
battery life of the host application.