Digi International Inc XBEEPRO2 Manual De Usuario

Parent and remote devices must be configured to buffer data correctly and to utilize adequate transmission 
timeouts. See the XBee Router / Coordinator Configuration section in this chapter for details.

Cyclic sleep allows the module to sleep for a specified time and wake for a short time to poll its parent for any 
buffered data messages before returning to sleep again. Cyclic sleep mode is enabled by setting the SM 
command to 4 or 5. SM5 is a slight variation of SM4 that allows the module to be woken prematurely by 
asserting the Sleep_RQ pin (pin 9). In SM5, the XBee can wake after the sleep period expires, or if a high-to-
low transition occurs on the Sleep_RQ pin. Setting SM to 4 disables the pin wake option.

In cyclic sleep, the module sleeps for a specified time, and then wakes and sends a poll request to its parent to 
discover if the parent has any pending data for the end device. If the parent has buffered data for the end 
device, or if serial data is received, the XBee will remain awake for a time. Otherwise, it will enter sleep mode 
immediately. 

The On/Sleep line is asserted (high) when the module wakes, and is de-asserted (low) when the module sleeps. 
If hardware flow control is enabled (D7 command), the CTS pin will assert (low) when the module wakes and 
can receive serial data, and de-assert (high) when the module sleeps.