LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
System description
Page 23 of 103
Removing
VCC
is not required though
Off
current will continue to be drawn from
VCC
source. However, if
VCC is removed, then ensure
VCC
pin and
V_INT
pin is 0V before powering back on. Refer to section
1.6.4.1 for details.
•
Modem is off
The following figure shows the power-off sequence and timing.
VCC
V_INT
P WR _ON
Interface S ignals
R E S E T_N
S ys tem S tate
Interface S tate
Operational
OF F
Tristate / F loating
ON
Operational
→
Tristate / F loating
AT+CPWROFF
sent to the module
0 ms
X ms
X + 10 sec
OK
replied by the module
Remove all interface signals
Figure 9
:
Module power up timing and sequence of supply and signals
When designing a host application for robustness, typically it covers a scenario in which the OK response is not
returned after issuing AT+CPWROFF to LISA-C200. To add robustness for such a case, wait 20 seconds after
issuing the command, and if OK has yet to be returned then as a last option perform either one of these actions:
•
Apply a hard reset using asserting RESET_N low for 300 to 500 ms. Refer to section 1.6.4.4 for further
details on applying reset.
•
Apply an under-voltage shutdown. Refer to section 1.6.2 for more details.
1.6.4.4
Reset
Preferred method using AT command
•
Issue
AT+CFUN=1
AT command, either via UART or USB
•
Time to reset is approximately 200 ms; after reset time, the modem is ready for normal operation
•
Alternative method using
RESET_N
pin, when the AT command method not possible
•
Ensure modem has been powered on for at least 10 sec
•
Pull
RESET_N
pin low for 300 to 500 ms (max)
•
Modem requires a minimal of 10 sec before another reset with this method and be reattempted
1.6.5
Key points to system functions
This section is a collection of key points from section 1.6 regarding Supply, Power-on/off, and Reset. The goal is
to point out important key points to avoid common errors and to avoid misuse.
Power supply
•
Handle any sudden momentary power loss gracefully as described in section 1.5.2.1