Specifications

AC65/AC75 Hardware Interface Description

3.6 Power Saving

AC65_AC75_HD_v01.002 Page 46 of 117 2006-10-30

Confidential / Released

3.6 Power Saving

Intended for power saving, SLEEP mode reduces the functionality of the AC65/AC75 to a minimum and thus min-

imizes the current consumption. Settings can be made using the AT+CFUN command. For details see [1].

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 CYCLIC 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 allows the AC65/AC75 to wake up for the duration of an

event and, afterwards, to resume power saving. Please refer to [1] for a summary of all SLEEP modes and the

different ways of waking up the module.

For CYCLIC SLEEP mode both the AC65/AC75 and the application must be configured to use hardware 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 [1] for details on how to configure hardware flow control for

the AC65/AC75.

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 registered 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.

Figure 10: Power saving and paging

The varying pauses explain the different potential for power saving. The longer the pause the less power is con-

sumed.

0.47-2.12 s

0.47-2.12 s 0.47-2.12 s

Paging

Power Saving