> 3.3.3 | Turn off TC65

> TC65 can be turned off as follows:

> • | Normal shutdown: Software controlled by AT^SMSO command

> • | Automatic shutdown: Takes effect if board or battery temperature is out of range or if undervoltage or overvoltage conditions occur.

> 3.3.3.1 | Turn off TC65 Using AT Command

> The best and safest approach to powering down TC65 is to issue the AT^SMSO command. This procedure lets TC65 log off from the network and allows the software to enter into a secure state and safe data before disconnecting the power supply. The mode is referred to as Power-down mode. In this mode, only the RTC stays active.
> Before switching off the device sends the following response:
> ^SMSO: MS OFF
> OK
> ^SHUTDOWN
> After sending AT^SMSO do not enter any other AT commands. There are two ways to verify when the module turns off:

> • | Wait for the URC “^SHUTDOWN”. It indicates that data have been stored non-volatile and the module turns off in less than 1 second.

> • | Also, you can monitor the PWR_IND pin. High state of PWR_IND definitely indicates that the module is switched off.

> Be sure not to disconnect the supply voltage V BATT+ before the URC “^SHUTDOWN” has been issued and the PWR_IND signal has gone high. Otherwise you run the risk of losing data. Signal states during turn-off are shown in Figure 9.
> While TC65 is in Power-down mode the application interface is switched off and must not be fed from any other source. Therefore, your application must be designed to avoid any current flow into any digital pins of the application interface, especially of the serial interfaces. No special care is required for the USB interface which is protected from reverse current.
> .
> Figure 9: Signal states during turn-off procedure
> Note: Depending on capacitance load from host application

> 3.3.3.2 | Leakage Current in Power-Down Mode

> The leakage current in Power-down mode varies depending on the following conditions:

> • | If the supply voltage at BATT+ was disconnected and then applied again without starting up the TC65 module, the leakage current ranges between 90 µA and 100 µA.

> • | If the TC65 module is started and afterwards powered down with AT^SMSO, then the leakage current is only 50 µA.

> Therefore, in order to minimize the leakage current take care to start up the module at least once before it is powered down.

> 3.3.3.3 | Turn on/off TC65 Applications with Integrated USB

> In a Windows environment, the USB COM port emulation causes the USB port of TC65 to appear as a virtual COM port (VCOM port). The VCOM port emulation is only present when Windows can communicate with the module, and is lost when the module shuts down. Therefore, the host application or Terminal program must be disconnected from the USB VCOM port each time the module is restarted.
> Restart after shutdown with AT^SMSO:
> After entering the power-down command AT^SMSO on one of the interfaces (ASC0, ASC1, USB) the host application or Terminal program used on the USB VCOM port must be closed before the module is restarted by activating the IGT line.
> Software reset with AT+CFUN=x,1:
> Likewise, when using the reset command AT+CFUN=x,1 on one of the interfaces (ASC0, ASC1, USB) ensure that the host application or Terminal program on the USB VCOM port be closed down before the module restarts.
> Note that if AT+CFUN=x,1 is entered on the USB interface the application or Terminal program on the USB VCOM port must be closed immediately after the response OK is returned.