iSource+â¢ Low Cost HPFRS Manual - Spectratime

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iSource+ Low Cost HPFRS Manual4.4 PIN FUNCTION LAYOUTThe complete pin layout for the sub-D connector is given in figure 4.4.HPFRS-01HPFRS-0210K1 : Lock monitor2 : Frequency adj.3 : GND4 : Lamp monitor5 : RxD (TTL)6 : Heating +24V7 : Xtal monitor8 : +5Vref.9 : Power +24V10 : Power returnA1 : Frequency Output10K1 : Lock monitor2 : Frequency adj.3 : GND4 : TxD (TTL)5 : RxD (TTL)6 : Power +24V (12V)7 : NC8 : +5Vref.9 : Power +24V (12V)10 : GNDA1 : Frequency OutputFig. 4.4 (connector front view)IMPORTANT NOTE:The standard version of the HPFRS is equipped with sub-D type Cannon 11W1 male togetherwith male coaxial connector.This configuration reduces the risks of damage to the coaxial HPFRS connector by incorrectmanipulations.4.5 NORMAL OPERATIONWhen 24 Vdc is applied to pins 6, 9 (+) and 3, 10 (-), the unit will immediately begin to generate a 10 MHzsignal from the crystal oscillator. Within approximately 8 minutes (standard version) after application of inputpower the unit will "lock". Hence the crystal is now stabilised by the atomic resonant frequency.The unit is able to provide a single signal called ‘lock monitor’ (pin 1) which toggles when the internal crystaloscillator is locked to the Rb atomic resonance. (see chapter 4.7).The centre frequency can be adjusted by external trimmer according to fig. 4.4 or by a stable DC voltageprovided by the user.ANALOG FREQUENCY ADJUSTMENTThe HPFRS is equipped with an analog frequency adjustment circuit which provides center frequencyadjustment by applying an external voltage of 0 to 5V on Pin 2.This analog voltage can be generated with an external potentiometer connected to Vref and GND (see pinfunction layout).©SpectraTime Europe Headquarters North America Sales Offices Page 10 of 13sales@spectratime.com +41.32.732.16.66 +1.512.470.3980spectratime.com
iSource+ Low Cost HPFRS Manual4.6 SERIAL INTERFACE OPERATION4.6.1 INTRODUCTIONThe HPFRS is equipped with a microcomputer, associated with multi-channel D/A converters, used for settingits parameters. This microcomputer is also used for the interrogation and detection of the Rb absorption ‘ dip’ .The built-in serial interface allows an automatic parameter adjustment during the manufacturing process as wellas coarse and fine adjustment of the centre frequency.All the working parameters are stored in a built-in EEPROM memory. In addition an 8 channel A/D converter isused for monitoring the main internal signals such as: light level, signal level , thermostats heating currentsetc...4.6.2 SERIAL INTERFACE CONNECTIONThe data transfer from the HPFRS can be made by direct connection to a PC or standard terminal .The data transfer parameters are the following :bit rate : 1200 bits/s.parity : nonestart bit: 1data bits: 8stop bit: 1IMPORTANT NOTE:The serial HPFRS interface accepts the 0 to 5V level and a direct connection can be made. TheHPFRS RxD input is protected and can accept ±12V RS 232 standard voltage also.4.6.3 HPFRS-02 INTERNAL PARAMETERS MONITORINGThe HPFRS-01 is only equipped with RxD pin on the connector. Therefore, it can only receive commands forfrequency adjustment. (no monitoring capabilities by RS 232 interface).Consequently, the HPFRS has no internal parameter monitoring capability.4.6.4 CENTRE FREQUENCY ADJUSTMENT WITH THE SERIAL INTERFACETwo single character commands are available to the user for centre frequency adjustment. This correction(coarse or fine) is automatically loaded into the internal EEPROM memory and becomes permanent .Cxx: Coarse output frequency correction through the synthesiser, by steps of 2 x 10 -10 for the HPFRS-01 and 1 x 10 -9 per step for the HPFRS-02 model.where xx is a signed 8 bits word(HEX coded).Example for HPFRS-01 model:‘C7F‘ will produce +2.54 x 10 -8 freq. correction from the nominal value 0‘CFF‘ will produce -2 x 10 -10‘C00‘ return to the nominal value (factory setting)‘C80‘ will produce -2.56 x 10 -8 freq. correction from nominal value 0Example for HPFRS-02 model:‘C7F‘ will produce +1.28 x 10 -7 freq. correction from the nominal value 0‘CFF‘ will produce -1 x 10 -9‘C00‘ return to the nominal value (factory setting)‘C80‘ will produce -1.27 x 10 -7 freq. correction from nominal value 0Fxx: Fine output frequency correction through C-field, by steps of 1 x 10 -11where xx is a signed 8 bits word(HEX coded).©SpectraTime Europe Headquarters North America Sales Offices Page 11 of 13sales@spectratime.com +41.32.732.16.66 +1.512.470.3980spectratime.com
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