Single-Chip Low Cost Low Power RF-Transceiver (Rev. B

CC250029 General Purpose / Test Output Control PinsThe three digital output pins GDO0, GDO1 andGDO2 are general control pins configured withIOCFG0.GDO0_CFG, IOCFG1.GDO1_CFGand IOCFG2.GDO2_CFG respectively. Table33 shows the different signals that can bemonitored on the GDO pins. These signals canbe used as inputs to the MCU. GDO1 is thesame pin as the SO pin on the SPI interface,thus the output programmed on this pin willonly be valid when CSn is high. The defaultvalue for GDO1 is 3-stated, which is usefulwhen the SPI interface is shared with otherdevices.The default value for GDO0 is a 135-141 kHzclock output (XOSC frequency divided by 192).Since the XOSC is turned on at power-onreset,this can be used to clock the MCU insystems with only one crystal. When the MCUis up and running, it can change the clockfrequency by writing to IOCFG0.GDO0_CFG.An on-chip analog temperature sensor isenabled by writing the value 128 (0x80) to theIOCFG0.GDO0_CFG register. The voltage onthe GDO0 pin is then proportional totemperature. See Section 4.7 on page 15 fortemperature sensor specifications.If the IOCFGx.GDO0_CFG setting is less than0x20 and IOCFGx_GDOx_INV is 0 (1), theGDO0 and GDO2 pins will be hardwired to 0 (1)and the GDO1 pin will be hardwired to 1 (0) inthe SLEEP state. These signals will behardwired until the CHIP_RDYn signal goeslow.If the IOCFGx.GDO0_CFG setting is 0x20 orhigher the GDO pins will work as programmedalso in SLEEP state. As an example, GDO1 ishigh impedance in all states ifIOCFG1.GDO0_CFG=0x2E.SWRS040B Page 53 of 92