A member of the Olancha Group Ltd
Registered in England No. 08405712
VAT Registration No. GB163 04 0349
Siretta Ltd
Basingstoke Road
Spencers Wood
Reading
Berkshire RG7 1PW
sales
fax
email
web
+44(0)118 976 9014
+44(0)118 976 9020
www.siretta.co.uk
41
ZETA Series
GPRS/UMTS/LTE Terminal with GPIO
Considerations when manually powering the ZETA on and off
The PWRON_IN and PWROFF_IN signals requires a positive “edge” (a “sharp” signal
transition from low to high) to turn the modem on. This transition should be a rising
signal from 0V (GND) up to Vcc (max 42V), or at least a large fraction of that voltage
range (>0.5V). Very slow transitions (significantly slower than many milliseconds) or
very small transitions (e.g. only a few millivolts instead of 0V to 0.5V) will not turn on
the modem (since they are not considered to be a “positive edge”).
Although this will not be an issue in almost all typical applications of the modem,
under the following condition special design care has to be taken:
»
Large capacitors in your power supply which will lead to slow leading and falling
edges
The case above might prevent the modem from recognizing the power-up signal.
This is no failure of the modem itself, the same would apply to almost any electronic
device that provides a separate “power-on” or “reset” signal.
If you are in doubt, please use the following recommendations:
»
Use the Vcc power supply signal from the main supply to test the power on signal
function.
»
Make sure that your signal and system design adheres to the recommendations
mentioned above
»
Consult our support team and we will be more than happy to assist you.
Disaster recovery power down reset procedure
The ZETA modems do not have any special power down reset functionality for
disaster recovery.
In the event of the standard power down functions failing using the PWROFF_IN pin
or the software shutdown AT command then power must be removed completely
from the modem.
Wait for a minimum of 10 seconds and then apply mains power to put the modem in
to the startup state.
NOTE
- Powering down the the modem without following the correct procedure using the
shutdown command or the hardware PWROFF_IN pin can result in improper functioning of the
modem. It will also not detach safely from the GSM network and may cause the terminal to
become blacklisted.
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