Applicant: Motorola, INC
Serial Interface during Low Power Mode
During low power mode the serial interfaces are inactive.
The module wakes up periodically from low power mode to page the network for any incoming calls or
data. After this short paging is completed, it returns to low power mode. During this short awake period,
the serial interfaces are enabled and communications with the module is possible.
The CTS_N signal is alternately enabled and disabled synchronously with the network paging cycle.
CTS_N is enabled whenever the module awakes to page the network. This indicates the serial interfaces
FIGURE 10 – CTS signal during Sleep mode
The periodical enabling and disabling of the CTS_N signal during low power mode can be controlled by
the AT+MSCTS command.
Setting AT+MSCTS=1 permanently disables the serial interface during low power mode, even during a
network page. The CTS_N signal is disabled, and therefore the serial interfaces are blocked.
Terminating low power mode
Terminating the low power mode, or wake-up, is defined as the transition of the module operating state
from Sleep mode to Idle mode. There are several ways to wake-up the module from low power mode, as
During low power mode the module's internal clocks and circuits are disabled, in order to minimize power
consumption. When terminating low power mode, and switching to Idle mode, the module requires a
minimal delay time to reactivate and stabilize its internal circuits before it can respond to application data.
This delay is maximum 15 milliseconds long, and is also indicated by the CTS_N signal inactive (high)
state. The delay guarantees that data on the serial interface is not lost or misinterpreted.
Temporary Termination of Low Power Mode
Motorola General Business Use
Page 13 of 36
FCC ID: IHDP56JE1
C24 Hardware Interface Manual