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

CC250030 Asynchronous and Synchronous Serial OperationSeveral features and modes of operation havebeen included in the CC2500 to providebackward compatibility with previous Chipconproducts and other existing RF communicationsystems. For new systems, it is recommendedto use the built-in packet handling features, asthey can give more robust communication,significantly offload the microcontroller andsimplify software development.30.1 Asynchronous operationFor backward compatibility with systemsalready using the asynchronous data transferfrom other Chipcon products, asynchronoustransfer is also included in CC2500. Whenasynchronous transfer is enabled, several ofthe support mechanisms for the MCU that areincluded in CC2500 will be disabled, such aspacket handling hardware, buffering in theFIFO and so on. The asynchronous transfermode does not allow the use of the datawhitener, interleaver, and FEC, and it is notpossible to use Manchester encoding.Note that MSK is not supported forasynchronous transfer.Setting PKTCTRL0.PKT_FORMAT to 3enables asynchronous serial mode.In TX, the GDO0 pin is used for data input (TXdata). Data output can be on GDO0, GDO1 orGDO2. This is set by the IOCFG0.GDO0_CFG,IOCFG1.GDO1_CFG and IOCFG2.GDO2_CFGfields.The CC2500 modulator samples the level of theasynchronous input 8 times faster than theprogrammed data rate. The timing requirementfor the asynchronous stream is that the error inthe bit period must be less than one eighth ofthe programmed data rate.30.2 Synchronous serial operationSetting PKTCTRL0.PKT_FORMAT to 1enables synchronous serial mode. In thesynchronous serial mode, data is transferredon a two wire serial interface. The CC2500provides a clock that is used to set up newdata on the data input line or sample data onthe data output line. Data input (TX data) is theGDO0 pin. This pin will automatically beconfigured as an input when TX is active. Thedata output pin can be any of the GDO pins;this is set by the IOCFG0.GDO0_CFG,IOCFG1.GDO1_CFG and IOCFG2.GDO2_CFGfields.Preamble and sync word insertion/detectionmay or may not be active, dependent on thesync mode set by the MDMCFG2.SYNC_MODE.If preamble and sync word is disabled, allother packet handler features and FEC shouldalso be disabled. The MCU must then handlepreamble and sync word insertion anddetection in software. If preamble and syncword insertion/detection is left on, all packethandling features and FEC can be used. Oneexception is that the address filtering feature isunavailable in synchronous serial mode.When using the packet handling features insynchronous serial mode, the CC2500 willinsert and detect the preamble and sync wordand the MCU will only provide/get the datapayload. This is equivalent to therecommended FIFO operation mode.31 System considerations and Guidelines31.1 SRD RegulationsInternational regulations and national lawsregulate the use of radio receivers andtransmitters. The most important regulationsfor the 2.4 GHz band are EN 300 440 and EN300 328 (Europe), FCC CFR47 part 15.247and 15.249 (USA), and ARIB STD-T66(Japan). A summary of the most importantaspects of these regulations can be found inApplication Note AN032 [2].Please note that compliance with regulationsis dependent on complete systemperformance. It is the customer’s responsibilityto ensure that the system complies withregulations.SWRS040B Page 55 of 92