N O V A T E L W I R E L E S S T E C H N O L O G I E S L T D .
2 2
A T C o m m a n d S p e c i f i c a t i o n - E x p e d i t e a n d M e r l i n
W i r e l e s s I P M o d e m s
Out-of-service Sleep Mode
The modem must be registered and within a reliable coverage area before it can actually go to
sleep for standard sleep mode. This means that the modem cannot sleep and will be in a higher
battery discharge state at all times that the modem is outside of CDPD coverage. The Out-of-
service Sleep Mode allows the modem to go to sleep during periods of no coverage. The modem
will sleep for some (usually relatively long) period and wake occasionally to see if it has returned
to a coverage area. The goal is to give the modem a battery life approaching that of standard
sleep mode when within CDPD coverage.
Out-of-service sleep mode is activated by sending the AT#NSZZ=1 command or deactivated by
sending the AT#NSZZ=0 command. This change must be saved with the AT&W command, and
the module must be reset before this change will take effect.
Following a loss of signal, the modem will make several attempts to find service on the currently
registered side before deciding that it is no longer registered and that it must search both sides for
service. Once this has occurred, or following modem initialization under no service conditions, the
modem will continue to search for a valid CDPD signal for the complete scan period. If no service
is found the modem will sleep for the sleep cycle length less the time that it was awake for the
search. After this sleep interval, the modem will wake for a brief search. If no service is found, it
will sleep again for the sleep cycle length less the brief scan period. This cycle continues with one
scan period in each cycle count periods being a complete scan. If the modem finds service and
registers during one of the scans, the out-of-service sleep mechanism is reset and waits for the
next time that service is lost.
To prematurely wake the modem up from out-of-service sleep mode, the wake-up signal can be
asserted for a minimum of 10 ms. The module will de-assert CTS when entering sleep mode to
inhibit the host from sending data but will periodically assert CTS and check for incoming serial
data from the host to prevent any loss of data.
Description:
These commands permit the user to define what the parameters of out-of-service sleep mode and to
enable or disable the operation of this mode. If out-of-service sleep mode does not appear to work with
your application, please contact Novatel Wireless for assistance. The default setting for this mode is off.
Format:
AT#NSZZ
Out-of-service Sleep status query command
AT#NSZZ=0
Disable out-of-service sleep feature
AT#NSZZ=1
Enable out-of-service sleep feature
AT#NSZZTM=p,b,c,n
Configure out-of-service sleep feature
p = sleep cycle length in seconds. This is the interval
between successive wakeups.
b = brief scan period in seconds. This is the time that
the modem will be awake for most of its waking intervals.
It is intended to be a brief look at the hot list of the
preferred side.
