User's Manual

XTend™RFModule‐ProductManual
©2013DigiInternatonal,Inc. 17
The period of time the module sleeps is determined by ST (Time before Sleep) Command. Once a
character is received through the DI pin, the module returns to Idle Mode and is fully operational.
Cyclic Sleep (SM = 4-8)
• Typical Power-down Current: < 1.6 mA (when asleep)
Cyclic Sleep Modes allow modules to periodically wake and check for RF data. The module wakes
according to the times designated by the Cyclic sleep settings. If the module detects a wake-up
initializer during the time it is awake, the module synchronizes with the transmitting module and
receives data after the wake-up initializer runs its duration. Otherwise, the module returns to
Sleep Mode and continues to cycle in and out of activity until a wake-up initializer is detected.
While the module is in Cyclic Sleep Mode, CTS
(GPO1) is de-asserted (high) to indicate that data
should not be sent to the module. When the module awakens to listen for data, GPO1 is asserted
and any data received on the DI Pin is transmitted. The PWR pin is also de-asserted (low) when
the module is in Cyclic Sleep Mode.
The module remains in Sleep Mode for a user-defined period of time ranging from 0.5 seconds to
16 seconds (SM parameters 4 through 8). After this interval of time, the module returns to Idle
Mode and listens for a valid data packet. The listen time will depend on the [BR] (RF Data Rate)
parameter setting.The default [BR] setting of 1 will require at least a 35ms wake time, while the
[BR] setting of 0 will require a wake time of up to 225ms. If the module does not detect valid data
(on any frequency), the module returns to Sleep Mode. If valid data is detected, the module
transitions into Receive Mode and receives the incoming RF packets. The module then returns to
Sleep Mode after a period of inactivity determined by the ST "Time before Sleep" parameter.
The module can also be configured to wake from cyclic sleep when the SLEEP pin is de-asserted.
To configure a module to operate in this manner, PW (Pin Wake-up) Command must be issued.
Once the SLEEP pin is de-asserted, the module is forced into Idle Mode and can begin transmitting
or receiving data. It remains active until data is no longer detected for the period of time specified
by the ST Command, at which point it resumes its low-power cyclic state.
Cyclic Scanning. Each RF transmission consists of an RF Initializer and payload. The RF initializer
contains initialization information and all receiving modules must wake during the wake-up
initializer portion of data transmission in order to be synchronized with the transmitting module
and receive the data.
The cyclic interval time defined by the SM (Sleep Mode) command must be shorter than the interval
time defined by LH (Wake-up Initializer Timer) command.
Figure2‐08. CorrectConfiguration(LH>SM):
Thelengthofthewake‐upinitializerexceedsthetimeintervalofCyclicSleep.Thereceiveris
guaranteedtodetectthewake‐upinitializerandreceivetheaccompanyingpayloaddata.
Command Mode
To modify or read module parameters, the module must first enter into Command Mode (state in
which incoming characters are interpreted as commands). Two command types are supported:
• AT Commands
• Binary Commands
For modified parameter values to persist in the module registry, changes must be saved to non-
volatile memory using the WR (Write) command. Otherwise, parameters are restored to previously
saved values when the module is powered off and then on again.