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USERS MANUAL
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If application wakeup events are used in combination with the module’s RTC sleep/wake cycle capabilities, the
module will disregard the <wake> period to power down and remain powered on. At this point it is expected
the application will start communicating with the module. The first action the application should perform is an
instruction to disable the RTC mode (AT+CFUN=1).
3.8.3
Ring Indicator Notes
The ring indicator pin assert-time can be configured via the PRI. It is not configurable through an AT
command.
As indicated by the CM52 Integrator’s Manual, the RI pin signal should not be considered valid at power up
until after the “Restart” unsolicited message is received by the application.
3.9
Real Time Clock (RTC)
The real time clock is a feature provided by the CM52 that allows the module to sleep and wakeup for a
definable number of cycles, as configured by the host application. This feature is an optional hardware feature
that is controlled by software. The module/RTC can be programmed so that the module will sleep and be
awake at definable times without continuous application intervention.
The RTC is typically used for applications that have sleep times where no activity is necessary for a specified
length of time. Activities that involve the module happen on a scheduled basis (for instance, a meter reading
application). Such an application may only need to wake up once a month to provide the current meter value
to a network application. The module and the network are synchronized to the same time schedule.
Another application usage would be to use the RTC in combination with the application wake-up feature. The
module could be programmed to a wake/sleep cycle and perform typical network functions during the wake
time. Specific events could trigger the host application to wake up. The host application can remain powered
down to reduce power consumption.
The RTC will share the MODULE_PWR_EN_B pin with the host application to wakeup and reset the module.
As a result, there are a few scenarios that are described in AT+CFUN that need to be adhered to. Minimum
sleep times have been defined to eliminate cases where the module and host application could get into a
suspended state.
The RTC currently has a time granularity of 1 minute, meaning the solution is not aware of seconds. As a
result, if the RTC is to wake the module up in 2 minutes and the current time is 10:10:40, the module will
actually wake up in 1:20 because the 40 seconds is not accounted for.
From an application standpoint, it is recommended that the wakeup, scan and securing service be considered
when determining when the next module wakeup should occur. The time between powering on the module
and going idle will vary depending upon the MRU, PRL and surrounding service. Observations indicate that
going idle could take up to 45 seconds in worst case scenarios. Accounting for the module startup time will
ensure that the module is idle during the defined interval where it is to be “waiting” for incoming requests.
3.10 Serial
Port
Multiplexer
The multiplexer provides the following three logical communication channels on the serial port: AT commands,
data, and unsolicited messages. Each channel can be in use at all times. As a result, the AT commands can
be issued and unsolicited messages can be received while the module is on a data call. The multiplexer also
provides optional CRC error checking and retransmission. Upon request, SEMC can provide sample
multiplexer source code that can be used on the host application.
3.10.1
Module Device Driver (MDD)
SEMC also provides a higher-layer product, the Module Device Driver or MDD, which builds on the
functionality of the multiplexer. MDD can be compiled into the host application. MDD provides a complete
