LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
System description
Page 21 of 103
1.6.2
Module power-off
The correct way to switch off LISA-C200 and FW75-C200 modules is by means of the +CPWROFF AT command
(more details in
u-blox C2 series AT Commands Manual
[3]). Using this method, internal software tasks are
properly terminated, the current parameter settings are saved in the module’s non-volatile memory, and a
proper network detach is performed.
An under-voltage shutdown will be done if the
VCC
supply is removed, but in this case the internal software
tasks are interrupted, the current modem parameter settings are not saved in the module’s non-volatile memory,
and a proper network detach cannot be performed. Once the supply is removed, it takes minimally 2 seconds
after the voltage falls below 2.6 V to reach power-off state. It is advised to avoid performing an under-voltage
shutdown if not necessary. Do not perform an under-voltage shutdown or reset by asserting
RESET_N
pin low
until the module has been powered on for at least 10 seconds.
The module must have been powered on for at least 10 seconds before a hard reset or an under-
voltage can be applied. Failure to comply may result in unpredictable behavior and possible
memory corruption.
1.6.3
Module reset
The module reset can be performed by:
•
AT+CFUN command
(more details in
u-blox C2 series AT Commands Manual
[3]): in this case an “internal”
or “software” reset is performed, causing an asynchronous reset of the baseband processor. This is the
preferred method to perform a reset.
•
Forcing a low level on the
RESET_N
input pin, causing an “external” or “hardware” reset (LISA-C200
only). Before performing a reset with this method, allow at least 10 sec for the module to stay powered on.
It is advised to minimize or to completely avoid performing a reset with this method
LISA-C200: The recommended hold time to reset modem is 300 ms to 500 ms. Longer hold times
approaching 1000 ms will cause the modem to power down.
The
RESET_N
function should NOT be used as a function to turn OFF the C200 modules. Use the
+CPWROFF to do so.
LISA-C200 provides an internal pull-up on the RESET_N pin: an open drain / collector driver is
recommended. Driving or pulling RESET_N high externally is NOT permitted.
The module must have been powered on for at least 10 seconds before a hard reset or an under-
voltage can be applied. Failure to comply may result in unpredictable behavior and possible
memory corruption.
1.6.4
Power-on, Power-off and Reset Sequences
This section describes the recommended sequencing to control the modem:
1.6.4.1
Power-on using PWR_ON method
•
Apply
VCC
•
Wait 50 ms
•
Ensure voltage at
V_INT
pin is 0V before next step (ie no back feed voltage)
•
Pull
PWR_ON
pin low for 300 ms (boot time)
•
Release
PWR_ON
pin back to high
•
Modem is operational after 3 sec
