Sleep Mode - Digi XTend User Manual

Sleep Mode

Software Sleep
Sleep Modes enable the module to enter states of low-power consumption when not in use. Three software Sleep
Modes are supported:
•
Pin Sleep (Host Controlled)
•
Serial Port Sleep (Wake on Serial Port activity)
•
Cyclic Sleep (Wake on RF activity)
In order to enter Sleep Mode, one of the following conditions must be met (in addition to the module having a non-
zero SM parameter value):
1. The module is idle (no data transmission or reception) for the amount of time defined by the ST (Time before
Sleep) parameter. [ST is only active when SM = 4-5.]
2. SLEEP (pin 8) is asserted (only for the Pin Sleep option).
When in Sleep Mode, the module will not transmit or receive data until the module first transitions to Idle Mode. All
Sleep Modes are enabled and disabled using SM Command. Transitions into and out of Sleep Modes are triggered by
various mechanisms as shown in the table below.
Sleep Mode
(Setting)
Pin Sleep
(SM = 1)
Serial Port
Sleep
(SM = 2)
Cyclic Sleep
(SM = 4 - 8)
The SM (Sleep Mode) command is central to setting all Sleep Mode configurations. By default, Sleep Modes are
disabled (SM = 0) and the module remains in Idle/Receive Mode. When in this state, the module remains constantly
ready to respond to serial or RF activity.
Refer to Hardware Sleep
current).
XTend RF Module User Guide
Transition into
Sleep Mode
Assert (high) SLEEP pin - A micro
controller can shut down and wake
modules via the SLEEP pin.
Note The module will complete a
transmission or reception
before activating Pin Sleep.
Automatic transition to Sleep Mode
occurs after a user-defined period of
inactivity (no transmitting or receiving
of data).
Period of inactivity is defined by the
ST (Time before Sleep) Command.
RF module transitions in and out of Sleep Mode in cycles (user-
selectable wake-up interval of time is set using the SM
command). The cyclic sleep interval of time must be shorter
than the interval of time that is defined by the LH (Wake-up
Initializer Timer) command.
Note The module can be forced into Idle Mode using the
SLEEP pin if the PW (Pin Wake-up) command is issued.
on page 19 to enable the module's lowest power-consuming state (5 µA typical power-down
Transition out of
Sleep Mode (wake)
De-assert (low) SLEEP
pin
When a serial byte is
received on the DI pin
Modes of operation
Related Power
Commands Consumption
(SM) < 147A
(SM), ST < 10 mA
(SM), ST, HT, < 1.6 mA
LH, PW
when sleeping
(SM=4, 1 sec.,
@120K baud)
20