u-blox SARA-R4 Series System Integration Manual

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SARA-R4 series - System Integration ManualUBX-16029218 - R06 System descriptionPage 19 of 1021.6 System function interfaces1.6.1 Module power-onWhen the SARA-R4 series modules are in the not-powered mode (i.e. the VCC module supply is not applied),they can be switched on as follows: Rising edge on the VCC input pins to a valid voltage level, and then a low logic level has to be held at thePWR_ON input pin for a valid time.When the SARA-R4 series modules are in the power-off mode (i.e. switched off) or in the PSM low power mode,with a valid VCC supply applied, they can be switched on as follows: Low pulse on the PWR_ON pin for a valid time periodThe PWR_ON input pin is equipped with an internal active pull-up resistor. Detailed electrical characteristics withvoltages and timings are described in SARA-R4 series Data Sheet [1].Figure 5 shows the module switch-on sequence from the not-powered mode, describing the following phases: The external power supply is applied to the VCC module pins The PWR_ON pin is held low for a valid time All the generic digital pins of the module are tri-stated until the switch-on of their supply source (V_INT). The internal reset signal is held low: the baseband core and all the digital pins are held in the reset state. When the internal reset signal is released, any digital pin is set in a proper sequence from the reset state tothe default operational configured state. The duration of this pins’ configuration phase differs within genericdigital interfaces and the USB interface due to host / device enumeration timings (see section 1.9.2). The module is fully ready to operate after all interfaces are configured.VCCPWR_ONRESET_NV_INTInternal ResetSystem StateBB Pads State Internal Reset → Operational OperationalInternalResetOFF ONTristate / FloatingStart of interfaceconfigurationModule interfacesare configuredStart-upevent~4.5 s0 sFigure 5: SARA-R4 series switch-on sequence descriptionThe Internal Reset signal is not available on a module pin, but the host application can monitor the V_INTpin to sense the start of the SARA-R4 series module switch-on sequence.Before the switch-on of the generic digital interface supply source (V_INT) of the module, no voltagedriven by an external application should be applied to any generic digital interface of the module.Before the SARA-R4 series module is fully ready to operate, the host application processor should notsend any AT command over the AT communication interfaces (USB, UART) of the module.The duration of the SARA-R4 series modules’ switch-on routine can vary depending on the application /network settings and the concurrent module activities.