BGS3 Hardware Interface Description
3.6 Power Saving
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BGS3_HD_v01.000d
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2010-03-26
Confidential / Released
3.6
Power Saving
Intended for power saving, SLEEP mode reduces the functionality of the BGS3 to a minimum
and thus minimizes the current consumption. Settings can be made using the AT+CFUN com-
mand. For details see
. SLEEP mode falls in two categories:
•
NON-CYCLIC SLEEP mode: AT+CFUN = 0
•
CYCLIC SLEEP modes, AT+CFUN = 7 or 9.
The functionality level AT+CFUN=1 is where power saving is switched off. This is the default
after startup.
NON-CYCLIC SLEEP mode permanently blocks the serial interface. The benefit of the CY-
CLIC SLEEP mode is that the serial interface remains accessible and that, in intermittent wake-
up periods, characters can be sent or received without terminating the selected mode. This al-
lows the BGS3 to wake up for the duration of an event and, afterwards, to resume power sav-
ing. Please refer to
for a summary of all SLEEP modes and the different ways of waking up
the module.
For CYCLIC SLEEP mode both the BGS3 and the application must be configured to use hard-
ware flow control. This is necessary since the CTSx signal is set/reset every 0.9-2.7 seconds
in order to indicate to the application when the UART is active. Please refer to
for details on
how to configure hardware flow control for the BGS3.
Note: Although not explicitly stated, all explanations given in this section refer equally to ASC0
and ASC1, and accordingly to CTS0 and CTS1 or RTS0 and RTS1.
3.6.1
Network Dependency of SLEEP Modes
The power saving possibilities of SLEEP modes depend on the network the module is regis-
tered in. The paging timing cycle varies with the base station. The duration of a paging interval
can be calculated from the following formula:
t = 4.615 ms (TDMA frame duration) * 51 (number of frames) * DRX value.
DRX (Discontinuous Reception) is a value from 2 to 9, resulting in paging intervals from
0.47-2.12 seconds. The DRX value of the base station is assigned by the network operator.
In the pauses between listening to paging messages, the module resumes power saving, as
shown in
.
Figure 10:
Power saving and paging
The varying pauses explain the different potential for power saving. The longer the pause the
less power is consumed.
