> 3.3.1 | Turn on TC65

> TC65 can be started in a variety of ways as described in the following chapters:

> • | Hardware driven start-up by IGT line: starts Normal mode or Airplane mode (see Section 3.3.1.1)

> • | Software controlled reset by AT+CFUN command: starts Normal mode or Airplane mode (see Section 3.3.1.4)

> • | Hardware driven start-up by VCHARGE line: starts charging algorithm and charge-only mode (see Section 3.3.1.3)

> • | Wake-up from Power-down mode by using RTC interrupt: starts Airplane mode

> The option whether to start into Normal mode or Airplane mode depends on the settings made with the AT^SCFG command or AT+CALA. With AT+CALA, followed by AT^SMSO the module can be configured to restart into Airplane mode at a scheduled alarm time. Switching back and forth between Normal mode and Airplane mode is possible any time during operation by using the AT^SCFG command.
> After startup or mode change the following URCs indicate the module’s ready state:

> • | “SYSSTART” indicates that the module has entered Normal mode.

> • | ^SYSSTART AIRPLANE MODE” indicates that the module has enstered Airplane mode.

> • | ^SYSSTART CHARGE ONLY MODE” indicates that the module has entered the Charge-only mode.

> These URCs are indicated only if the module is set to a fixed bit rate, i.e. they do not appear if autobauding is enabled (AT+IPR≠0).
> Detailed explanations on AT^SCFG, AT+CFUN, AT+CALA, Airplane mode and AT+IPR can be found in [1].

> 3.3.1.1 | Turn on TC65 Using Ignition Line IGT

> When the TC65 module is in Power-down mode or Charge-only mode, it can be started to Normal mode or Airplane mode by driving the IGT (ignition) line to ground. This must be accomplished with an open drain/collector driver to avoid current flowing into this pin.
> The module will start up when both of the following two conditions are met:

> • | The supply voltage applied at BATT+ must be in the operating range.

> • | The IGT line needs to be driven low for at least 400ms in Power-down mode or at least 2s in Charge-only mode.

> Considering different strategies of host application design the figures below show two approaches to meet this requirement: The example in Figure 5 assumes that IGT is activated after BATT+ has already been applied. The example in Figure 6 assumes that IGT is held low before BATT+ is switched on. In either case, to power on the module, ensure that low state of IGT takes at least 400ms (Power-down mode) or 2s (Charge-only mode) from the moment the voltage at BATT+ is available. For Charge-only mode see also Section 3.3.1.3 and Section 3.5.7.
> Assertion of CTS indicates that the module is ready to receive data from the host application. In addition, if configured to a fixed bit rate (AT+IPR≠0), the module will send the URC “^SYSSTART” or “^SYSSTART AIRPLANE MODE” which notifies the host application that the first AT command can be sent to the module. The duration until this URC is output varies with the SIM card and may take a couple of seconds.
> Please note that no “^SYSSTART” or “^SYSSTART AIRPLANE MODE” URC will be generated if autobauding (AT+IPR=0) is enabled.
> To allow the application to detect the ready state of the module we recommend using hardware flow control which can be set with AT\Q or AT+ICF (see [1] for details). The default setting of TC65 is AT\Q0 (no flow control) which shall be altered to AT\Q3 (RTS/CTS handshake). If the application design does not integrate RTS/CTS lines the host application shall wait at least for the “^SYSSTART” or “^SYSSTART AIRPLANE MODE” URC. However, if the URCs are neither used (due to autobauding) then the only way of checking the module’s ready state is polling. To do so, try to send characters (e.g. “at”) until the module is responding.
> See also Section 3.3.2 "Signal States after Startup”.
> Figure 5: Power-on with operating voltage at BATT+ applied before activating IGT
> Figure 6: Power-on with IGT held low before switching on operating voltage at BATT+
> If the IGT line is driven low for less than 400ms the module will, instead of starting up, send only the alert message “SHUTDOWN after Illegal PowerUp” to the host application. The alert message appears on the serial interfaces ASC0 and ASC1 at a fixed bit rate of 115200 bps. If other fixed bit rates or autobauding are set, the URC delivers only undefined characters. The message will not be indicated on the USB interface.

> 3.3.1.2 | Configuring the IGT Line for Use as ON/OFF Switch

> The IGT line can be configured for use in two different switching modes: You can set the IGT line to switch on the module only, or to switch it on and off. The switching mode is determined by the parameter "MEShutdown/OnIgnition" of the AT^SCFG command. This approach is useful for application manufacturers who wish to have an ON/OFF switch installed on the host device.
> By factory default, the ON/OFF switch mode of IGT is disabled:

> at^scfg=meshutdown/onignition ^SCFG: "MEShutdown/OnIgnition","off" OK | # Query the current status of IGT. # IGT can be used only to switch on TC65. IGT works as described in Section 3.3.1.1.

> To configure IGT for use as ON/OFF switch:

> at^scfg=meshutdown/onignition ^SCFG: "MEShutdown/OnIgnition","on" OK | # Enable the ON/OFF switch mode of IGT. # IGT can be used to switch on and off TC65.

> We strongly recommend taking great care before changing the switching mode of the IGT line. To ensure that the IGT line works properly as ON/OFF switch it is of vital importance that the following conditions are met.
> Switch-on condition: If the TC65 is off, the IGT line must be asserted for at least 400ms before being released. The module switches on after 400ms.
> Switch-off condition: If the TC65 is on, the IGT line must be asserted for at least 1s before being released. The module switches off after the line is released. The switch-off routine is identical with the procedure initiated by AT^SMSO, i.e. the software performs an orderly shutdown as described in Section 3.3.3.1. Before switching off the module wait at least 2 seconds after startup.
> Figure 7: Timing of IGT if used as ON/OFF switch

> 3.3.1.3 | Turn on TC65 Using the VCHARGE Signal

> As detailed in Section 3.5.7, the charging adapter can be connected regardless of the module’s operating mode.
> If the charger is connected to the charger input of the external charging circuit and the module’s VCHARGE pin while TC65 is off, and the battery voltage is above the undervoltage lockout threshold, processor controlled fast charging starts (see Section 3.5.6). TC65 enters a restricted mode, referred to as Charge-only mode where only the charging algorithm will be launched.
> During the Charge-only mode TC65 is neither logged on to the GSM network nor are the serial interfaces fully accessible. To switch from Charge-only mode to Normal mode the ignition line (IGT) must be pulled low for at least 2 seconds. When released, the IGT line goes high and causes the module to enter the Normal mode. See also Section 3.3.3.1.

> 3.3.1.4 | Reset TC65 via AT+CFUN Command

> To reset and restart the TC65 module use the command AT+CFUN. You can enter AT+CFUN=,1 or AT+CFUN=x,1, where x may be in the range from 0 to 9. See [1] for details.
> If configured to a fix baud rate (AT+IPR≠0), the module will send the URC "^SYSSTART" or "^SYSSTART AIRPLANE MODE" to notify that it is ready to operate. If autobauding is enabled (AT+IPR=0) there will be no notification. To register to the network SIM PIN authentication is necessary after restart
> .

> 3.3.1.5 | Reset or Turn off TC65 in Case of Emergency

> Note: Use the EMERG_RST pin only when, due to serious problems, the software is not responding for more than 5 seconds. Pulling the EMERG_RST pin causes the loss of all infor mation stored in the volatile memory. Therefore, this procedure is intended only for use in case of emergency, e.g. if TC65 does not respond, if reset or shutdown via AT command fails.
> The EMERG_RST signal is available on the application interface. To control the EMERG_RST line it is recommended to use an open drain / collector driver.
> The EMERG_RST line can be used to switch off or to reset the module. In any case the EMERG_RST line must be pulled to ground for >600ms. Then, after releasing the EMERG_RST line the module restarts if IGT is held low for at least 400ms. Otherwise, if IGT is not low the module switches off. In this case, it can be restarted any time as described in Section 3.3.1.1.
> After hardware driven restart, notification via “^SYSSTART” or “^SYSSTART AIRPLANE” URC is the same as in case of restart by IGT or AT command. To register to the network SIM PIN authentication is necessary after restart.

> 3.3.1.6 | Using EMERG_RST Signal to Reset Application(s) or External Device(s)

> When the module starts up, while IGT is held low for 400ms, the EMERG_RST signal goes low for 120ms as shown in Figure 5 and Figure 6. During this 120ms period, EMERG_RST becomes an output which can be used to reset application(s) or external device(s) connected to the module.
> After the 120ms period, i.e. during operation of the module, the EMERG_RST is an input.
> Specifications of the input and output mode of EMERG_RST can be found in Table 30.

> 3.3.1.7 | Automatic Restart after Shutdown

> If the design of your final product implies that the module can restart automatically after a power-down event you may take advantage of a reset logic such as described below. A typical procedure that requires the module to restart automatically is, for example, updating the TC65 firmware over the air (see [7] Application Note 17: Over-The-Air Firmware Update). The described circuit can also be useful if you wish to restart the module when an unexpected shutdown has occurred.
> Such a circuit is capable to react to a status change of the PWR_IND line and implement a pause of at least 600ms before restarting the module by pulling IGT low for at least 400ms.
> Figure 8 shows a sample circuit (as an alternative the duo-diode D1 can be replaced with the pn-junctions of two transistors of the same type). The components used in a particular application shall be dimensioned depending on the environmental operating temperature the application is intended for.
> Figure 8: Sample circuit to implement ignition after power down