SAMBA 75 USER’S GUIDE
VERSION 1.01
supply. The mode is referred to as Power-down mode. In this mode, only the RTC
stays active.
Before switching off the device sends the following response:
^SMSO: MS OFF
OK
^SHUTDOWN
After sending AT^SMSO do not enter any other AT commands. There are two ways to
verify when the module turns off:
•
Wait for the URC “^SHUTDOWN”. It indicates that data have been
stored non-volatile and the module turns off in less than 1 second.
Be sure not to disconnect the supply voltage (SMABA75 modem) before the URC
“^SHUTDOWN” has been issued. Otherwise you run the risk of losing data. While
SAMBA 75 is in Power-down mode the application interface is switched off.
5.2.3 Automatic Shutdown
Automatic shutdown takes effect if
•
the SAMBA 75 board is exceeding the critical limits of
overtemperature or undertemperature
The automatic shutdown procedure is equivalent to the Power-down initiated with
the AT^SMSO command, i.e. SAMBA 75 logs off from the network and the software
enters a secure state avoiding loss of data.
Alert messages transmitted before the device switches off are implemented as
Unsolicited Result Codes (URCs). The presentation of these URCs can be enabled or
disabled with the two AT commands AT^SBC and AT^SCTM. For further instructions of
the AT commands refer to [3].
5.3 Automatic EGPRS/GPRS Multislot Class Change
Temperature control is also effective for operation in EGPRS Multislot Class 10, GPRS
Multislot Class 10 and GPRS Multislot Class 12. If the board temperature increases to
the limit specified for restricted operation
1)
while data are transmitted over EGPRS or
GPRS, the module automatically reverts:
•
from EDGE Multislot Class 10 (2 Tx slots) to EEDGE Multislot Class 8 (1
Tx),
•
from GPRS Multislot Class 12 (4 Tx slots) to GPRS Multislot Class 8 (1 Tx)
•
from GPRS Multislot Class 10 (2 Tx slots) to GPRS Multislot Class 8 (1 Tx)
This reduces the power consumption and, consequently, causes the board’s
temperature to decrease. Once the temperature drops to a value of 5 degrees
below the limit of restricted operation, SAMBA 75 returns to the higher Multislot Class.
If the temperature stays at the critical level or even continues to rise, SAMBA 75 will
not switch back to the higher class. After a transition from EGPRS Multislot Class 10 to
EGPRS Multislot Class 8 a possible switchback to EGPRS Multislot Class 10 is blocked
for one minute. The same applies when a transition occurs from GPRS Multislot Class
12 or 10 to GPRS Multislot Class 8. Please note that there is not one single cause of
switching over to a lower Multislot Class. Rather it is the result of an interaction of
several factors, such as the board temperature that depends largely on the ambient
temperature, the operating mode and the transmit power. Furthermore, take into
account that there is a delay until the network proceeds to a lower or, accordingly,
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