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58 page 
CC1100E SWRS082 Page 58 of 92 The CC1100E is highly suited for FHSS or multi- channel systems due to its agile frequency synthesizer and effective communication interface. Using the packet handling support and data buffering is also beneficial in such systems as these features will significantly offload the host controller. Charge pump current, VCO current, and VCO capacitance array calibration data is required for each frequency when implementing frequency hopping for the CC1100E. There are 3 ways of obtaining the calibration data from the chip: 1) Frequency hopping with calibration for each hop. The PLL calibration time is approximately 720 µs. The blanking interval between each frequency hop is then approximately 810 us. 2) Fast frequency hopping without calibration for each hop can be done by performing the necessary calibrating at startup and saving the resulting , , and register values in MCU memory. The VCO capacitance array calibration FSCAL1 register value must be found for each RF frequency to be used. The VCO current calibration value and the charge pump current calibration value are not dependent on the RF frequency, so the same value can therefore be used for all RF frequencies for these two registers. Between each frequency hop, the calibration process can then be replaced by writing the FSCAL3, and FSCAL1 register values that corresponds to the next RF frequency. The PLL turn on time is approximately 90 µs. The blanking interval between each frequency hop is then approximately 90 µs. 3) Run calibration on a single frequency at startup. Next write 0 to FSCAL3 [5:4] to disable the charge pump calibration. After writing to FSCAL3 , strobe SRX (or ) with MCSM0.FS_AUTOCAL=1 for each new frequency hop. That is, VCO current and VCO capacitance calibration is done, but not charge pump current calibration. When charge pump current calibration is disabled the calibration time is reduced from approximately 720 µs to approximately 150 µs. The blanking interval between each frequency hop is then approximately 240 µs. There is a trade off between blanking time and memory space needed for storing calibration data in non-volatile memory. Solution 2) above gives the shortest blanking interval, but requires more memory space to store calibration values. This solution also requires that the supply voltage and temperature do not vary much in order to have a robust solution. Solution 3) gives approximately 570 µs smaller blanking interval than solution 1). The recommended settings for changes with frequency. This means that one should always use SmartRF ® Studio [8] to get the correct settings for a specific frequency before doing a calibration, regardless of which calibration method is being used. 28.3 Data Burst Transmissions The high maximum data rate of the CC1100E opens up for burst transmissions. A low average data rate link (e.g. 10 kBaud) can be realized by using a higher over-the-air data rate. Buffering the data and transmitting in bursts at high data rate (e.g. 500 kBaud) will reduce the time in active mode, and hence also reduce the average current consumption significantly. Reducing the time in active mode will reduce the likelihood of collisions with other systems in the same frequency range. 28.4 Continuous Transmissions In data streaming applications, the CC1100E opens up for continuous transmissions at a 500 kBaud effective data rate. As the modulation is done with a closed loop PLL, there is no limitation in the length of a transmission (open loop modulation used in some transceivers often prevents this kind of continuous data streaming and reduces the effective data rate). Note: The content in the TESTn registers (n = 0, 1, or 2) are not retained in SLEEP state, thus it is necessary to re-write these registers when returning from the SLEEP state. Note: The sensitivity and thus transmission range is reduced for high data rate bursts compared to lower data rates. |
