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9XCite‐PKG‐R™RS‐232/485RFModem–ProductManualv2.1[2007.01.04]

©2007MaxStream,Inc. 16

into Idle Mode to listen for valid data packets and de-asserts when the modem returns to Sleep

Mode.

The modem remains in Sleep Mode for a user-defined period of time ranging from 0.5 seconds to

16 seconds (SM Parameters 3 through 8). After this interval of time, the modem returns to Idle

Mode and listens for a valid data packet for 100 ms. If the modem does not detect valid data (on

any frequency), the modem returns to Sleep Mode. If valid data is detected, the modem transi-

tions into Receive Mode and receives the incoming packets. The modem then returns to Sleep

Mode after a Period of inactivity that is determined by ST "Time before Sleep" Parameter.

The modem can also be configured to Wake-up from cyclic sleep when the SLEEP pin is de-

asserted (low). To configure a modem to operate in this manner, PW (Pin Wake-up) Command

must be issued. Once the Sleep pin is de-asserted, the modem is forced into Idle Mode and can

begin transmitting or receiving data. It remains active until no data is detected for the period of

time specified by the ST parameter, at which point it resumes its low-power cyclic state.

Note: The cyclic interval time defined by SM (Sleep Mode) Command must be shorter than the interval

time defined by LH ("Wake-up Initializer Timer") Command. For example: If SM=4 (Cyclic 1.0 second

sleep), the LH Parameter should equal 0xB ("1.1" seconds). With these parameters set, there is no risk

of the receiving modem being asleep for the duration of the wake-up initializer transmission. The fol-

lowing section "Cyclic Scanning" explains in further detail the relationship between "Cyclic Sleep" and

"Wake-up Initializer Timer"

Cyclic Scanning. Each RF transmission consists of a wake-up initializer and payload data. The

wake-up initializer contains initialization information and all receiving modems must Wake-up dur-

ing the wake-up initializer portion of data transmission in order to synchronize with the transmitter

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3‐06. 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.

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