Clike here to get datasheet of CC1101 - Elechouse

CC1101After the automatic power-on reset or manualreset it is also recommended to change thesignal that is output on the GDO0 pin. Thedefault setting is to output a clock signal with afrequency of CLK_XOSC/192, but to optimizeperformance in TX and RX an alternative GDOsetting should be selected from the settingsfound in Table 33 on page 56.19.1.1 Automatic PORA power-on reset circuit is included in theCC1101. The minimum requirements stated inTable 12 must be followed for the power-onreset to function properly. The internal powerupsequence is completed when CHIP_RDYngoes low. CHIP_RDYn is observed on the SOpin after CSn is pulled low. See Section 10.1for more details on CHIP_RDYn.When the CC1101 reset is completed the chipwill be in the IDLE state and the crystaloscillator will be running. If the chip has hadsufficient time for the crystal oscillator tostabilize after the power-on-reset the SO pinwill go low immediately after taking CSn low. IfCSn is taken low before reset is completed theSO pin will first go high, indicating that thecrystal oscillator is not stabilized, before goinglow as shown in Figure 17.Figure 17: Power-On Reset19.1.2 Manual ResetThe other global reset possibility on CC1101uses the SRES command strobe. By issuingthis strobe, all internal registers and states areset to the default, IDLE state. The manualpower-up sequence is as follows (see Figure18):• Set SCLK = 1 and SI = 0, to avoidpotential problems with pin control mode(see Section 11.3 on page 28).• Strobe CSn low / high.• Hold CSn high for at least 40µs relative topulling CSn low• Pull CSn low and wait for SO to go low(CHIP_RDYn).• Issue the SRES strobe on the SI line.• When SO goes low again, reset iscomplete and the chip is in the IDLE state.XOSC and voltage regulator switched onCSnSOSI40 usSRESXOSC StableFigure 18: Power-On Reset with SRESNote that the above reset procedure is onlyrequired just after the power supply is firstturned on. If the user wants to reset the CC1101after this, it is only necessary to issue an SREScommand strobe.19.2 Crystal ControlThe crystal oscillator (XOSC) is eitherautomatically controlled or always on, ifMCSM0.XOSC_FORCE_ON is set.In the automatic mode, the XOSC will beturned off if the SXOFF or SPWD commandstrobes are issued; the state machine thengoes to XOFF or SLEEP respectively. Thiscan only be done from the IDLE state. TheXOSC will be turned off when CSn is released(goes high). The XOSC will be automaticallyturned on again when CSn goes low. Thestate machine will then go to the IDLE state.The SO pin on the SPI interface must bepulled low before the SPI interface is ready tobe used; as described in Section 10.1 on page25.If the XOSC is forced on, the crystal willalways stay on even in the SLEEP state.Crystal oscillator start-up time depends oncrystal ESR and load capacitances. Theelectrical specification for the crystal oscillatorcan be found in Section 4.4 on page 13.SWRS061C Page 43 of 94