Using CC1000 for the Konnex standard

&KLSFRQ$SSOLFDWLRQ1RWH $1$1Using CC1000 for the Konnex standardKeywords• CC1000• Konnex standard• Increasing data rate• Modifying the crystal frequencyby T.A LunderIntroductionThe CC1000 is a highly integratedmultichannel FSK (Frequency Shift Keying)transceiver. Although it is designed to givefixed data rates for a specific crystal, thisapplication note describes how to find anew crystal frequency in order to get adesired data rate.The Konnex standard is a radio frequencyprotocol for building and home automation,and this note gives the details on how touse CC1000 to comply with this standard.Chipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 1 of 6

&KLSFRQ$SSOLFDWLRQ1RWH $1The konnex standardThe RF parameters for the konnex standard are given in the table bellow.Parameter Value Unit NoteRF frequency 868.3 MHzFreq tolerance +/- 25 ppmFSK deviation +/- 50 kHz Min +/- 40, max +/- 80 kHzCodingManchesterChiprate 32768 Kchip/s = kBaud Specify crystal frequencyData rate 16384 kbit/s Same as 16 kHz square waveChip rate tolerance 1.5 % Also related to crystal frequencyTX jitter +/- 1 usOutput power 0 dBm MinimumBlocking EN300220, class 2RX chip rate +/- 2 %toleranceRX sensitivity -95 dBm BER=10-4Preamble 15xchips 01Signal interface and crystal frequencyThe CC1000 offers a synchronous signal interface. That is, in transmit mode the CC1000provides a clock (DCLK) according to the selected data rate. The data input (DIO) should belatched using this clock. In receive mode the CC1000 provides a clock that is synchronouswith the incoming data rate together with the data output (DIO).To be able to use the synchronous mode for the Konnex standard, we need CC1000 togenerate a synchronisation signal on the DCLK for the given data rate. The frequencydiscriminator, data filtering and the data slicer are all handled by digital signal processing andare controlled by the MODEM0 register. The register information of MODEM0 is given below.REGISTER NAME DescriptionMODEM0[7] - Not usedMODEM0[6:4] BAUDRATE[2:0] 000 : 0.6 kbaud001 : 1.2 kbaud010 : 2.4 kbaud011 : 4.8 kbaud100 : 9.6 kbaud101 : 19.2kbaud110 : Not used111 : Not usedMODEM0[3:2] DATA_FORMAT[1:0] 00 : NRZ operation.01 : Manchester operation10 : Transparent Asyncronous UART operation11 : Not usedMODEM0[1:0] XOSC_FREQ[1:0] Selection of XTAL frequency range00 : 3MHz - 4MHz crystal, 3.6864MHz recommended01 : 6MHz - 8MHz crystal, 7.3728MHz recommended10 : 9MHz - 12MHz crystal, 11.0592 MHz recommended11 : 12MHz - 16MHz crystal, 14.7456MHz recommendedChipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 2 of 6

&KLSFRQ$SSOLFDWLRQ1RWH $1To be able to generate the baud rates given by BAUDRATE[2:0] we need to use therecommended crystal frequency. For the Konnex however we want to use a baud rate of32.768 kbaud. To generate a data rate higher than specified with the recommended crystalfrequency, it is possible to program XOSC:FREQ corresponding to a crystal frequency that ishalf of the actually crystal frequency. In this case the demodulator is “fooled” to work at twicethe speed and thus twice the data rate. We must for the Konnex case find a crystal frequencygiving a baud rate of 16.384 kbaud, and then reduce the XOSC_FREQ[1:0] to correspond to acrystal frequency that is half the one we are using.The easiest way to find the crystal frequency for a given data rate is to use the formula:XTAL _ new =XTAL _ SRFS * BAUDRATE _ newBAUDRATE _ SRFShereXTAL_SRFS: The recommended values for accurate data rates (3.6864, 7.3728,11.0592, 14.7456 MHz).BAUDRATE_SRFS: The accurate data rate for the given XTAL_SRFS (0.6, 1.2, 2.4, 4.8,9.6 19.2 kbaud).The MODEM0 value for the new data rate can then be calculated in SmartRF Studio (SRFS)by the XTAL_SRFS and BAUDRATE_SRFS.If we use:XTAL_SRFS = 7.3728 MHzBAUDRATE_SRFS=19.2 kbaudBAUDRATE_NEW=32.768 kHz (Konnex)Then(7.3728MHz) *(32.768kbaud)XTAL _ new == 12. 582912MHz19.2kbaudGiving a baud rate of 32.768 kbaud.This crystal frequency gives an accurate baud rate that complies with the Konnex standard.However using this crystal frequency, the frequency for optimal sensitivity will have an offset infrequency of 229.1 kHz from 868.3 MHz. This crystal frequency can not be used if optimalsensitivity is required. If optimal sensitivity is required, then the crystal frequency value mustbe changed so that both the optimal frequency and the data rate complies with the Konnexstandard. Changing the crystal frequency to 12.586060 MHz gives an offset of 11.9 kHz and adata rate of 32.778 kbaud. A summery of the crystal frequency is given in the table below.Crystalfrequency[MHz]Data rate[kbaud]Channelfrequency [MHz]Offset from 868.3 MHz[kHz]12.582912 32.768 868.3 0 No12.586060 32.778 868.2881 11.9 Yes**Spreadsheet for finding closest optimal channels is available from Chipcon.OptimalsensitivityBy using the same approach as above, but in asynchronous mode (UART) the data rate canalso be increased to rates not being multiples of the standard data rates (i.e. 1.2, 2.4, 4.8 kbit/sChipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 3 of 6

&KLSFRQ$SSOLFDWLRQ1RWH $1and so on). In this mode the data clock (DCLK) is not used, so the over-sampling and thesynchronisation must be done externally, by a microcontroller, or by an UART.The Konnex protocolA preheader that has a Manchester Violation is used in the konnex standard. TheSynchronous Manchester mode can for this reason not be used in the TX mode of CC1000during transmission of this Preheader.In Rx mode the settling of the averaging filter in CC1000 require a balanced baud in thepreamble. In Manchester mode the chip stream must be ’100110011001…’ during thepreamble to ensure correct bit synchronisation. The Konnex preamble is however a chipstream of ‘0101010101’.PreheaderPreamble Manchester Sync word Postambleviolation15x ‘01’ chip ‘000111’ ‘011010010110’ 2-8 chipsDue to the Konnex preheader, CC1000 must use Synchronous NRZ mode and not useSynchronous Manchester mode. The Manchester coding must then be done in the MCU andthe datarate of this Manchester coded data need a datarate of 32.768 kbaud. Using thesynchronous NRZ mode, the preamble of balanced baud are ‘01010101..’, because the baudrate is the same as the bit rate in NRZ. Further the Manchester violation bit stream can easilybe implemented.In NRZ mode the settling time should be set to 01 to give a settling time of the averaging filterin the demodulator to 32 baud. In NRZ the baud rate is equal to the bit rate, and the Konnexrequire that the receiver are able to receive valid data after the preamble. This preamble is 30baud in NRZ mode, and it is ok for the CC1000 to use SETTLING=01 in MODEM1 Register.CC1000 Rx test for KonnexA preliminary test was performed using the calculated crystal frequency, in order to verify thatRX mode complies with the Konnex standard. During the test, a Signal Generator was used togive the Crystal frequency. The test result is given in the table below.Crystal SeparationMODEM0SensitivityfrequencyBAUDRATE DATA_FORMAT XOSC_FREQ12.586060 80 kHz 101 00 NRZ 01 -96 dBm12.586060 100 kHz 101 00 NRZ 01 -97 dBm12.586060 160 kHz 101 00 NRZ 01 -96 dBmTx data rate offset of 2% gives no effect on the sensitivity.Chipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 4 of 6

&KLSFRQ$SSOLFDWLRQ1RWH $1The blocking performance of CC1000 is given in the table below.Frequency offset CC1000 Requirement+/- 1 MHz 43 dB 30 dB+/- 2 MHz 49 dB 35 dB+/- 5 MHz 68 dB 50 dB+/- 10 MHz 72 dB 60 dBThe blocking result between +/- 10 MHz offset of 868 MHz is given in figure 1. This indicatesthat CC1000 complies with the blocking requirement of the Konnex standard.80706050dBc403020100855 860 865 870 875 880-10Figure 1: Blocking performance of CC1000 at 868 MHzCC1000 Tx test for KonnexThe synchronous data clock in transmit mode will also be scaled as shown above. The loopfilter bandwidth is adequate for baud rate at 32.768 kbaud but an optimisation of the PLLbandwidth could be done to improve the modulation response. A simple modulation analysiswas performed, and the time versus frequency plot showed a peak-to-peak separation of +/-120 kHz using a programmed frequency separation of 100 kHz. The Konnex require aseparation between 80-160 kHz, and CC1000 complies with the Konnex regarding modulation.In transmit mode the DCLK gives a signal equal to the data rate, and has no duty cycle offset.This informs us that there is no TX jitter on the transmitted signal.SummaryBy using a crystal frequency of 12.586060 MHz with a total accuracy of 11.5 ppm, the datarate and the frequency tolerance of the Konnex standard can be met. The sensitivity is –96dBm also meeting the standard.Chipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 5 of 6

&KLSFRQ$SSOLFDWLRQ1RWH $1This application note is written by the staff of Chipcon to the courtesy of our customers.Chipcon is a world-wide supplier of RFICs. For further information on the products fromChipcon please contact us or visit our web site. An updated list of distributors is also availableat our web site.Contact InformationAddress:Chipcon ASGaustadalléen 21N-0349 Oslo,NORWAYTelephone : (+47) 22 95 85 44Fax : (+47) 22 95 85 46E-mail : wireless@chipcon.comWeb site : http://www.chipcon.comDisclaimerChipcon AS believes the furnished information is correct and accurate at the time of this printing. However, ChipconAS reserves the right to make changes to this application note without notice. Chipcon AS does not assume anyresponsibility for the use of the described information. Please refer to Chipcon’s web site for the latest update.Chipcon AS AN010 Using C1000 for the konnex standard (Rev. 1.0) 2001-11-27 Page 6 of 6