Serial Interface During Low Power Mode; Terminating Low Power Mode; Temporary Termination Of Low Power Mode; Wkupi_N Signal Operation - Motorola W24 Technical Information

Low Power Mode

Serial Interface During Low Power Mode

During low power mode the W24 serial interfaces are disabled.
The W24 wakes up periodically from low power mode to monitor the network for data. After this
short paging is completed, W24 returns to low power mode. During this short awake period, the
serial interfaces are enabled and communications with the module is possible.

Terminating Low Power Mode

To bring W24 back from the sleep mode, WKUPI_N needs to be asserted (set low). The W24
Sleep mode is enabled or disabled by the AT+iPSE command. To permanently terminate the W24
Sleep mode, the AT+iPSE=0 command is used. W24 does not enter Sleep mode until an
AT+iPSE>0 command is sent.
Important:

Temporary Termination of Low Power Mode

Temporary termination of low power mode occurs when W24 switches from Sleep mode to Idle
mode for a defined period, and then returns automatically to Sleep mode.
Low power mode may be terminated temporarily by several sources, some of which are user
initiated and others are initiated by the system.
Using the WKUPI_N signal
The WKUPI_N signal is an active low input, that is set high by default. By asserting this signal
low the application can wake-up W24 from low power mode and switch to Idle mode.
W24 will remain in Idle mode, awake and fully active, as long as WKUPI_N signal remains low.
When this signal is disabled and set high again, W24 will return to Sleep mode automatically,
according to the AT+iPSE settings (see
Figure 2-7: WKUPI_N Signal Operation
18
During power save mode the W24 internal clocks and circuits are disabled, in order
to minimize power consumption. When terminating the power saving mode, and
switching to Idle mode, W24 requires a minimal delay time to reactivate and
stabilize its internal circuits before it can respond to application data. This delay is
typically 5 milliseconds. The delay guarantees that data on the serial interface is not
lost or misinterpreted.
Figure
Module Hardware Description
2-7).
May 31, 2008