u-blox SARA-R4 Series, Руководство по системной интеграции

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SARA-R4 series - System Integration Manual
UBX-16029218 - R06 System description
Page 21 of 102
Figure 7 describes the SARA-R4 series modules switch-off sequence started by means of the PWR_ON input pin,
allowing storage of current parameter settings in the module’s non-volatile memory and a proper network
detach, with the following phases:

A low pulse with appropriate time duration (see SARA-R4 series Data Sheet [1]) is applied at the PWR_ON
input pin.

At the end of the switch-off routine, all the digital pins are tri-stated and all the internal voltage regulators
are turned off, including the generic digital interfaces supply (
V_INT ).

Then, the module remains in power-off mode as long as a switch on event does not occur (e.g. applying a
proper low level to the
PWR_ON
input ), and enters not-powered mode if the
VCC
supply is removed.
VCC
PWR_ON
RESET_N
V_INT
Internal Reset
System State
BB Pads State
OFF
Tristate / Floating
ON
Operational
->
Tristate
Operational
0 s ~2.5 s ~5 s
The module starts
the switch-off routine
VCC can be
removed
Figure 7: SARA-R4 series switch-off sequence by means of PWR_ON pin
The Internal Reset signal is not available on a module pin, but it is recommended to monitor the V_INT
pin to sense the end of the switch-off sequence: VCC supply can be removed only after V_INT goes low.
The duration of each phase in the SARA-R4 series modules’ switch-off routines can largely vary depending
on the application / network settings and the concurrent module activities.
1.6.3 Module reset
SARA-R4 series modules can be properly reset (rebooted) by:

AT+CFUN command (see SARA-R4 series AT Commands Manual [2]).
In the case listed above an “internal” or “software” reset of the module is executed: the current parameter
settings are saved in the module’s non-volatile memory and a proper network detach is performed.
An abrupt hardware shutdown occurs on SARA-R4 series modules when a low level is applied on
RESET_N
input
pin for a valid time period. In this case, the current parameter settings are not saved in the module’s non-volatile
memory and a proper network detach is not performed. Then, the module remains in power-off mode as long
as a switch on event does not occur applying a proper low level to the
PWR_ON
input.
It is highly recommended to avoid an abrupt hardware shutdown of the module by forcing a low level on
the
RESET_N input during modules normal operation: the RESET_N line should be set low only if reset or
shutdown via AT commands fails or if the module does not provide a reply to a specific AT command
after a time period longer than the one defined in the
SARA-R4 series AT Commands Manual [2].
The
RESET_N
input pin is equipped with an internal pull-up to a 1.8 V supply domain. Detailed electrical
characteristics with voltages and timings are described in SARA-R4 series Data Sheet [1].