1756HP-GPS-IRIG-OUT User Manual
Contents
1. Status Offline Cancel Figure 5 3 Configure module s parameters Apply Help Page 9 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 W Module Properties Local 4 1756 MODULE 1 1 xj General Connection Module Info Backplane Requested Packet Interval RPI 10 ms 0 2 750 0 ms T Inhibit Module I Major Fault On Controller If Connection Fails While in Run Mode m Module Fault Status Running Figure 5 4 Configure module s RPI Requested Packet Interval The first word of the Configuration Image configures the module as a 1756HP GPS IRIG OUT Set the first word of the image to 0x01 If the user is using RSLogix 5000 v16 the UTC time base is different from previous versions of RSLogix To ensure that ControlLogix PLC s running different versions can be time synced using the 1756HP GPS IRIG OUT module the user must select if v16 is used or not The last bit least significant bit of the second byte of the configuration image configures the module to use or not use v16 UTC time By setting the bit the module will use v16 UTC time The highest bit most significant bit of the second byte of the configuration image configures the module to be the CST master By setting this bit the module will attempt to become the CST master If a CST master is present it will not become the CST master and indicate that a duplicate master was detected Configuration Image BYTE VALUE 0 0x01 12. 1 Current position in West hemisphere Current North South Hemisphere 0 Current position in North hemisphere 1 Current position in South hemisphere Local s I Data 0 23 Local s I Data 0 24 Local s I DatafJ0J 25 BIT BIT BIT Page 13 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 IRIG OUT Module Configuration 1 Module has been configured as an IRIG OUT IRIG OUT iiodula Local s I Dataf0J 26 BIT 0 Module not configured as IRIG OUT A duplicate CST master has been detected Dup Master 0 No duplicate CST master detected Local s 1 Data 0 28 BIT 1 A duplicate CST master is detected This module is the local rack CST master CST Master 0 This module is not the CST master Local s 1 Data 0 29 BIT 1 This module is the CST master Reserved Local s l Data o 30 31 BIT SV Count Satellite count Local s I Data 1 DINT Number of Satellites currently being tracked Calendar Year Year Current Local Calendar Year Local s 1 Data 2 DINT This is dependent on the configured time zone O e 2 Calendar Month Month Current Local Calendar Month 1 12 Local s 1 Data 3 DINT This is dependent on the configured time zone O e 2 Calendar Day of Month Day Current Local Calendar Day 1 31 Local s 1 Data 4 DINT This is dependent on the configured time zone O e 2 Real Time Hours Hours Current Local time Hours 0 23 Local s 1 Data 5 DINT This is dependent on the configured time
3. 5 monitor ground stations 1 master control ground station and 3 upload ground stations GPS Antenna An antenna designed to receive GPS radio navigation signals These antennas typically comprise a Low Noise Amplifier LNA and are known as active and thus require DC power GPS Processor An electronic device that interprets the GPS radio navigation signals received by a GPS antenna and determines a location solution GPS Receiver The combination of a GPS antenna and a GPS processor Owner controller The controller that creates and stores the primary configuration and communication connection to a module PDOP Position Dilution of Precision PDOP is a unitless figure of merit that describes how an uncertainty in pseudo range affects position solutions gt 4 Page 40 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 PRN Pseudo random noise Each GPS satellite generates its own distinctive PRN code which is modulated onto each carrier The PRN code serves as identification of the satellite as a timing signal and as a subcarrier for the navigation data Producer consumer Intelligent data exchange system devices in which the GPS module produces data without having been polled first Removal and insertion under power RIUP ControlLogix feature that allows a user to install or remove a module or RTB while power is applied Requested packet interval RPI A configurable parameter which defines when the module will multi
4. MainTask MainProgram Unscheduled Programs H E Motion Groups 29 Trends m Data Types c g auon New Module GUL Figure 5 1 Right click on I O Configuration and select New Module Pi Page 8 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 Select Module Type x Type Major Revision 1756 MODULE fi Description 1756 L1 ControlLogix5550 Controller 1756 L53 ControlLogix5553 Controller 1756 L55 ControlLogix5555 Controller 1756 L63 ControlLogix5563 Controller 1756 MO024E 2 Axis Analog Encoder Servo 8 Axis SERCOS Interface Generic 1756 Module 1756 0416 16 Point 74 265v AC Output 1756 0416 16 Point 74V 265V AC Isolated Output 1756 048 8 Point 74 265 AC Output 1756 048D 8 Point 74 132 AC Diagnostic Output 1756 048E 8 Point 4V 132V AC Electronically Fused Output xl Show Vendor fal MV Other M Specialty 1 0 Select All IV Analog V Digital V Communication V Motion V Controller Clear All Cancel Help Figure 5 2 Select Generic 1756 Module 1756 MODULE M Module Properties Local 3 1756 MODULE 1 1 General Connection Module Info Backplane Type 1756 MODULE Generic 1756 Module Name r our Input Description a Output Configuration 4 Comm Format Data DINT X Status Input 3 Slot eal Status Output Parent Local r Connection Parameters Assembly Instance Size 29 32bit 3 32bit 2 8 bit
5. TYPES This Appendix provides a detailed description of recommended data structures that can be used in conjunction with the provided example ladder code The following structures and example code can be downloaded from the Hiprom website www hiprom com B 1 Input Image Structures Data of the 1756HP GPS IRIG OUT can be presented clearly by copying the input image to the GPSImage user defined data type UDT structure This structure utilizes the following embedded UDT structures detailed below e GPSPolar e GPSENU e GPSCartesian GPSImage Name Data Type Style Reserved INT Decimal ModuleOk BOOL Decimal GPSLock BOOL Decimal CSTOk BOOL Decimal TimeOk BOOL Decimal PPS BOOL Decimal BatteryOk BOOL Decimal AntennaOk BOOL Decimal PDOPOk BOOL Decimal West BOOL Decimal South BOOL Decimal IRIG OUT BOOL Decimal Reserved1 BOOL Decimal Dup Master BOOL Decimal CST Master BOOL Decimal Reserved2 BOOL Decimal Reserved3 BOOL Decimal SatelliteCount DINT Decimal Year DINT Decimal Month DINT Decimal Day DINT Decimal Hour DINT Decimal Minute DINT Decimal Second DINT Decimal Microsecond DINT Decimal UTC DINT 2 Decimal CST DINT 2 Decimal gt 4 Page 27 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CSTOffset D
6. a cold start i e no almanac The module will take approximately 5 minutes to acquire Lock Once a complete almanac has been downloaded the time to achieve fix will be reduced to around 45 seconds An IRIG signal will only be transmitted once GPS lock has been acquired lt Page 7 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 5 CONFIGURING THE MODULE A direct connection between the controller and the 1756HP GPS IRIG OUT module is required to transfer I O data to and from the module In addition the module supports various unconnected messages that can be used to retrieve particular information 5 1 Establishing the Direct Connection This section describes the procedures necessary to configure the 1756HP GPS IRIG OUT module within the ControlLogix system Each 1756HP GPS IRIG OUT module must be owned by a single ControlLogix controller The 1756 Generic Module is used in RSLogix5000 to configure the module The configuration of the module is detailed in the table below Data Format CommFormat Data DINT Connection parameters Description Instance Size Input 1 29 Output 2 3 Configuration 4 2 RPI Min 1 0 msec Max 750 0 msec Table 5 1 1756HP GPS IRIG OUT connection parameters The steps required to add a new 1756HP GPS IRIG OUT module are detailed below E Controller GPS EG3 A Controller Tags Controller Fault Handler Power Up Handler S Tasks E fa
7. frame DOO m 1 iii iii oo a ig EREN A REN RG ZERO IRIG ONE PTA om ill j Anh A ANAN nn 20 f f oe N es i T sly VU ll il Ht f N AYA YAYIYIN VW N I VW Wy WU J y i i f Vy VUUNV pe iy U gt 4 Page 39 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 APPENDIX 6 G LO S SA RY Communications format Format that defines the type of information transferred between an I O module and its owner controller This format also defines the tags created for each O module Coordinated System Time CST Timer value which is kept synchronized for all modules within a single ControlBus chassis The CST is a 64 bit number with us resolution Coordinated System Time CST Download The process of transferring the contents of a project on the workstation into the controller Earth Centered Earth Fixed ECEF coordinates Cartesian coordinate system where the X direction is the intersection of the prime meridian Greenwich with the equator The vectors rotate with the earth Z is the direction of the spin axis with positive through the north pole GPS Global Positioning System A constellation of 24 radio navigation not communication satellites which transmit signals used by GPS receivers to determine precise location position velocity and time solutions GPS signals are available world wide 24 hours a day in all weather conditions This system also includes
8. internal clock which is constantly corrected using the GPS clocks This timing pulse is synchronized to UTC within 95 ns In addition to serving as a highly accurate stand alone time source GPS receivers are used to synchronize distant clocks in communication or data networks This synchronization is possible since all GPS satellite clocks are corrected to a common master clock Therefore the relative clock error is the same regardless of which satellite or satellites are used For timing applications requiring a common clock GPS is the ideal solution The position and time errors are related by the speed of light Therefore a position error of 100 meters corresponds to a time error of approximately 333 ns P Page 36 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 4PPENbEX E TIME STANDARDS There are many different time standards used in the world today This chapter describes the different formats and standards used in the 1756HP GPS IRIG OUT module and how the relate to one another E 1 GPS Time By synchronizing with the atomic clocks on GPS satellites the 1756HP GPS IRIG OUT module is able to compute accurate GPS time GPS time differs from UTC Universal Coordinated Time by a variable integer number of seconds UTC GPS time GPS UTC Offset As of April 2002 the GPS UTC offset was 13 seconds The offset increases by 1 second approximately every 18 months The 1756HP GPS IRIG OUT module automatically acquires the U
9. synchronized with the atomic clocks located on the GPS satellites The module supports IRIG B 122 the time is transmitted in an IRIG signal to IRIG devices via an external port This document serves to describe the functionality installation configuration and use of the module Page 3 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 2 MODULE ACCESSORIES Each 1756HP GPS IRIG OUT package includes the following components 1756HP GPS IRIG OUT module 1756HP GPS IRIG OUT user manual IRIG Breakout and 500mm patch lead 5m RG58 patch lead with a SMA male and TNC male connector on either end 3 3V active 500 bullet antenna Figure 2 1 1756HP GPS IRIG OUT module with antenna and patch lead es Page 4 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 3 MODULE OPERATION The 1756HP GPS IRIG OUT module is designed to operate within the Allen Bradley ControlLogix PLC system All power required for the module s operation is derived from the 1756 backplane HIPROM GPS Alphanumeric Display Status LEDs 4 External IRIG Interface Port SMA Antenna Port configuration Figure 3 1 1756HP GPS IRIG OUT Layout The 1756HP GPS IRIG OUT on board GPS receiver is connected via the external SMA antenna port and external antenna patch lead to the active GPS antenna As soon as the module is powered up it will begin searching for available GPS satellites Soon after lo
10. unconnected time conversion services namely e CST gt UTC and Gregorian UTC gt Gregorian This allows the user by means of a custom message service to convert between different time formats The conversion is valid only for time data that is less than 1 hour old P Page 6 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 4 INSTALLING THE MODULE GPS utilizes a spread spectrum signal in the 1 5GHz range and thus cannot penetrate conductive or opaque surfaces Thus the antenna should be mounted in a horizontal position with an unobstructed view of the sky Attach the antenna patch lead to the antenna It is recommended that waterproofing tape be used to seal the connection Nels Should a longer patch lead be required it is recommended that a GPS signal booster is used Contact your local Hiprom distributor for assistance The module is equipped with a RIUP Removal and Insertion Under Power circuitry enabling the module to be installed or removed from the chassis while power is applied Attach the patch lead SMA male to the module s SMA female connector It is not recommended that the antenna patch lead exceed a total loss of 10dB at 1 5GHZ as this may increase the time to GPS lock or in extreme cases prevent GPS lock from being achieved at all Attach the patch lead of the IRIG BREAKOUT to the module s RJ45 connector Once the module has been powered up for the first time it will search for satellites from
11. zone O e 2 Real Time Minutes Minutes Current Local time Minutes 0 59 Local s 1 Data 6 DINT This is dependent on the configured time zone O e 2 Real Time Seconds Seconds Current real time Seconds 0 59 Local s l Data 7 DINI Real Time Microseconds Ni Microseconds Current real time Microseconds 0 999 999 Local s l Data 8 DINT Current Universal Time Constant UTC Local s 1 Data 9 UTC To 64BIT Local s I Data 10 Current CLX Coordinate System Time CST Local s I Data 11 CST To 64BIT Local s I Data 12 Current CLX Coordinate System Time CST Offset Local s I Data 13 CST Offset Current Time CST CST Offset To 64BIT This is dependent on the configured time zone O e 2 Local s I Data 14 Latitude Current Position Latitude Degrees Local s I Data 15 Low INT Degrees 16Bit Latitude Current Position Latitude Minutes Local s I Data 15 High a yi INT Minutes 16Bit i Current Position Latitude Seconds Latitude Local s I Data 16 REAL Seconds Longitude Current Position Longitude Degrees Local s I Data 17 Low INT Degrees 16 Bit Longitude Current Position Longitude Minutes Local s Data 17 Minutes High 16 Bit INT i Current Position Longitude Seconds Longitude Local s I Data 18 REAL Seconds Current Position Altitude Altitude Meters above mean sea level Local s 1 Data 19 REAL Velocit Current Northerly Velocity elocity m s x 10 e North A negative value indicates a Southerly direction of Local s l Data 20 R
12. 0 lt 45 sec 90 Cold Start lt 90 sec 50 lt 170 sec 90 Antenna Antenna Connector SMA female connector Frequency Range 1575 42 MHz 1 023 MHz Polarization Right hand circular polarization RHCP Output Impedance 500 VSWR 2 0 maximum Axial Ratio 90 4 0 dB maximum 10 6 dB maximum Gain 35 dB 3 Db Out of Band Rejection fo 1575 42 MHz fo 20 MHz 7dB min fo 30 MHz 12dB min fo 40 MHz 20dB min fo 100 MHz 100dB min Azimuth Coverage 360 omni directional Elevation Coverage 0 to 90 elevation hemispherical Antenna Patch Lead Coax Type RG 58 Impedance 500 Page 31 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 APPENDIX b o GPS OPERATION The Global Positioning System GPS is a satellite based navigation system operated and maintained by the U S Department of Defence The system consists of a constellation of 24 satellites providing world wide 24 hour three dimensional 3D coverage Although originally conceived for military needs GPS has a broad array of civilian applications including surveying marine land aviation and vehicle navigation GPS is the most accurate technology available for vehicle navigation As a satellite based system GPS is immune to the limitations of land based systems such as Loran Loran navigation is limited in coverage and is enc
13. 0x Byte 1 X000 000Y binary where X will make the module a CST master if set to 1 and Y will make the module use v16 UTC time if set to 1 Once a modules configuration data has been downloaded to the controller it will attempt to establish a connection with the module A connection will fail if there is inappropriate configuration data Page 10 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 5 2 Coordinate System Time Master It is important that at least one controller or 1756HP GPS IRIG OUT module in the ControlLogix rack be configured as the Coordinate System Time master This can be configured in RSLogix5000 by right clicking on the Controller and selecting Properties Ensure that the checkbox as indicated below is checked to make the controller the CST master otherwise the procedure in section 5 1 above may be followed to make the 1756HP GPS IRIG OUT module the CST master i x General Serial Pott System Protocol UserProtocol MajorFauts Minor Faults Date Time Advanced Fle Redundancy Nonvolatile Memory Date and Time 2003 08 20 03 00 06 Pm Set jv Make this controller the Coordinated o DANGER If this setting is cleared System Time master online all active servo axes in any controller in the chassis will be Synchronized with a master Duplicate master detected Timer hardware faulted ok cano tory Hep Figure 5 5 Configu
14. 1756xp GPS IRIG OUT USER MANUAL gt chnolog E Mipcom Rev 2 6 March 2009 1756HP GPS IRIG OUT User Manual Rev 2 6 Table of Contents Chapter 1 ie e e ee Chapter 2 Module Accessories asalak sdesialim yaldek ba k Chapter 3 ModuleOperation Chapter 4 InstallingtheModule Chapter 5 ConfiguringtheModule Chapter 6 VOAddressMap Chapter 7 ModuleSpecificCommands Chapter 8 ModuleStatus Appendix A PLCLladderExample Appendix B RecommendedPLCDatalypes Appendix e 9 e eg e Appendix D GPSOperation Appendix E Timestandards Appendix F IRIGStandard Appendix GOS SAY cick aac sei ila eee Ain hentia ete Page 2 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 1 INTRODUCTION The 1756HP GPS IRIG OUT module provides accurate time and position information and services for the Allen Bradley ControlLogix PLC system A 1756HP GPS IRIG OUT makes use of Global Positioning System GPS technology to derive accurate time which is
15. EAL movement Page 14 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 Velocity East Velocity Upward ECEF Position X Current Easterly Velocity m s x 10 A negative value indicates a Westerly direction of movement Current Upward Velocity m s x 10 A negative value indicates a Downward direction of movement Distance from Earth centre along the X axis meters Position is calculated with respect to the WGS 84 Earth Centered Earth Fixed co ordinate system The X axis is defined as the vector with origin at the earth s centre and passing through the intersection of the equator and Greenwich meridian Local s 1 Data 21 Local s I Data 22 Local s I Data 23 REAL REAL REAL ECEF Position Y ECEF Position Z ECEF Velocity X ECEF Velocity Y ECEF Velocity Z Distance from Earth centre along the Y axis meters Position is calculated with respect to the WGS 84 Earth Centered Earth Fixed co ordinate system The Y axis is defined as the vector with origin at the earth s centre and passing through the equator 90 degrees east of the Greenwich meridian Distance from Earth centre along the Y axis meters Position is calculated with respect to the WGS 84 Earth Centered Earth Fixed co ordinate system The Z axis is defined as the vector with origin at the earth s centre and passing through the North pole Speed with respect to the X axis m
16. Field Bytes Type Description Satellite n Prn 1 SINT Satellite number 1 32 Satellite n Ele 1 SINT Elevation 0 90 Satellite n Azm 2 INT Azimuth 0 360 Satellite n SnR 4 DINT Signal noise ratio where n indicates the channel number 1 8 Table 7 2 Satellite data information response The above data structure is repeated for all 8 satellites thus giving a total length of 64 bytes for the response Refer to Appendix B for a recommended data structure for the satellite data Message Configuration GPSFetchSatDataMsg x Configuration Communication Tag Message Type C dn Service Custom Source Element Type Source Length fo Bytes Service ce 32 Hex Class 71 Hex Destination GPSSatData 7 Instance h Attribute 1 Hex F New Tag Eror Code Extended Eror Code I Timed Out Eror Path GPS Eror Text Cancel Apply Help Figure 7 1 Satellite data message structure Page 18 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 7 2 Converting Time Bases The 1756HP GPS IRIG OUT stores a rolling log of the CST UTC pairs for the last 1 hour Timestamps in a system can either be CST or UTC values The 1756HP GPS IRIG OUT module provides functionality for converting between values that are within the last hour 7 3 Converting CST to UTC and Gregorian By supplying the full 64 bit CST value the module will return the corresponding full Grego
17. INT 2 Decimal Latitude GPSPolar Degrees INT Decimal Minutes INT Decimal Seconds REAL Float Longitude GPSPolar Degrees INT Decimal Minutes INT Decimal Seconds REAL Float Altitude REAL Float Velocity GPSENU Northerly REAL Float Easterly REAL Float Upward REAL Float ECEFPosition GPSCartesian x REAL Float Y REAL Float Z REAL Float ECEF Velocity GPSCartesian X REAL Float Y REAL Float Z REAL Float Table B 1 GPSlmage UDT GPSPolar Name Data Type Style Degrees INT Decimal Minutes INT Decimal Seconds REAL Float Table B 2 GPSPolar UDT GPSENU Name Data Type Style Northerly REAL Float Easterly REAL Float Upward REAL Float Table B 3 GPSENU UDT KS 1756HP GPS IRIG OUT User Manual Rev 2 6 GPSCartesian Name Data Type Style X REAL Float Y REAL Float Z REAL Float Table B 4 GPSCartesian UDT B 2 Unconnected message Structures An array of the following structure can be used to receive the satellite data requested from the module via the unconnected message GPSSatData Name Data Type Style Prn SINT Decimal Ele SINT Decimal Azm INT Decimal Snr REAL Float Table B 5 GPSSatData UDT The following structure can be used for the CST to Gregorian conversion via the unconnected message The structure holds both the data sent and received GPSConvCST Name Data Type Style CSTRequest DIN
18. T 2 Decimal Year DINT Decimal Month DINT Decimal Day DINT Decimal Hour DINT Decimal Minute DINT Decimal Second DINT Decimal Microsecond DINT Decimal UTC DINT 2 Decimal CST DINT 2 Decimal Table B 6 GPSConvCST UDT Page 29 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 The following structure can be used for the UTC to Gregorian conversion via the unconnected message The structure holds both the data sent and received GPSConvUTC Name Data Type Style UTCReguest DINT 2 Decimal Year DINT Decimal Month DINT Decimal Day DINT Decimal Hour DINT Decimal Minute DINT Decimal Second DINT Decimal Microsecond DINT Decimal UTC DINT 2 Decimal Table B 4 GPSConvUTC UDT Page 30 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 APPENDIX c SPECIFICATIONS Parameter Specification General Module Location Any Slot Electrical Backplane Current 515mA 5 1V 3mA 24V Schedules Connection Paramters RPI 1 0ms to 750ms GPS Receiver Specification General L1 frequency 1575 42 MHz C A code Standard Positioning Service 8 channel continuous tracking receiver 32 correlators Accuracy Horizontal lt 6 meters 50 lt 9 meters 90 Altitude lt 11 meters 50 lt 18 meters 90 Velocity 0 06 m sec Time 95 ns or 1 RPI Hot Start lt 14 sec 50 lt 18 sec 90 Warm Start lt 38 sec 5
19. TC offset from the received GPS system almanac and calculates the correct UTC The 1756HP GPS IRIG OUT receiver makes use of the Extended GPS Week Number as the absolute number of weeks since the beginning of GPS time or January 6 1980 Using this rather than the true GPS Week Number prevents any possible roll over issues similar to Y2K that earlier generation GPS receivers suffered from E 2 Universal Coordinate Time UTC Universal Coordinate Time UTC is the world standard maintained by an ensemble of atomic clocks operated by government organizations around the world UTC time replaced GMT Greenwitch Mean Time as the world standard in 1986 GPS time is steered relative to Universal Coordinated Time UTC GPS does not recognize leap seconds resulting in the aforementioned GPS UTC Offset The 1756HP GPS IRIG OUT module reports UTC as a 64 bit unsigned long integer representing the number of elapsed microseconds since 1 January 1972 This UTC value is thus independent of the Configured Time Zone E 3 Local Time and Time Zone Configuration Local time is expressed in Gregorian format and takes into account the configured Time Zone The Time Zone is the difference between local and UTC time expressed as a REAL number of hours Nels The Time Zone set in the module s output image must be in REAL format Writing an integer directly to the module can cause unexpected results It is recommended that the GPSImage User defined Data Type be u
20. an initial position and time to be uploaded to the receiver via the serial port to initiate a warm start During a warm start the 1756HP GPS IRIG OUT receiver identifies the satellites which are expected to be in view given the system almanac the initial position and the approximate time The receiver calculates the elevation and expected Doppler shift for each satellite in this expected set and directs the eight tracking channels in a parallel search for these satellites The warm start time to first fix when the receiver has been powered down for more than 60 minutes i e the ephemeris data is old is usually less than 45 seconds Hot Start A hot start strategy applies when the 1756HP GPS IRIG OUT receiver has been powered down for less than 60 minutes and the almanac position ephemeris and time are valid The hot start search strategy is similar to a warm start but since the ephemeris data in gt 4 Page 33 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 memory is considered current and valid the acguisition time is typically less than 20 seconds 4 Page 34 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 D 3 Satellite Mask Settings Once the 1756HP GPS IRIG OUT receiver has acquired and locked onto a set of satellites which pass the mask criteria listed in this section and has obtained a valid ephemeris for each satellite it will output regular position velocity and time reports according to the protocol select
21. and the impact of reflected signals SNR Mask Although the 1756HP GPS IRIG OUT receiver is capable of tracking signals with SNRs as low as 0 the default SNR mask is set to 3 to eliminate poor quality signals from the fix computation and minimize constellation switching Low SNR values may result from e Low Elevation Satellites e Partially Obscured Signals e g Dense Foliage e Multi Reflected Signals Multi Path The distortion of signals and the frequent constellation switches associated with low elevation satellites were discussed above In mobile applications the attenuation of signals by foliage is typically a temporary condition Since the 1756HP GPS IRIG OUT receiver can maintain lock on signals with SNR s as low as 0 it offers excellent performance when traveling through heavy foliage Multi reflected signals also known as Multi path can degrade the position solution Multi path is most commonly found in urban environments with many tall buildings and a preponderance of mirrored glass which is gt 4 Page 35 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 popular in modern architecture Multi reflected signals tend to be weak low SNR value since each reflection attenuates the signal By setting the SNR mask to 3 the impact of multi reflected signals is minimized DOP Mask Position Dilution of Precision DOP is a measure of the error caused by the geometric relationship of the satellites used in the position solu
22. ata 0 Dest GPS Length 1 WRITE GPS Time Zone amp Logix CST to 1756HP GPS module GSV COP Get System Value Copy File Class name CST Source GPS Write CSTSet 0 Instance name Dest Local 2 0 Data 0 Attribute Name Current Yalue Length 5 Dest GPSWite CSTSet 0 622437257 Fetch Satellite Data Sat PRN Elevation Azimuth and Signal to Noise Ratio for each Receiver Channel GPSFetchSatDataEnable GPSFetchSatDataTm Dn TON Py Timer On Delay Timer GPSFetchS atDataT mr p Preset 5000 Accum MSG GPSFetchS atD ataT mr Dn Type CIP Generic Message Control Convert CST to Gregorian and UTC GPSConvertCSTEn MSG Type CIP Generic J Message Control GPSConvertCSTMsq E DD lt ERD GPSConvertCSTEn Convert CST to Gregorian and UTC GPSConvettUTCEn MSG Type CIP Generic Message Control GPSConvertUTCMsg E Ns GPSConvertUTCEn lt gt Synchronize the ControlLogix CPU with GPS Time CST Offset Method GPSSetWallClock Sv GPSSetWallClock Set System Value Class name WALLCLOCKTIME Instance name Attribute Name CSTOffset Source GPS CST Offset 0 1369022199 Synchronize the ControlLogix CPU with GPS Time Gregorian Method GPSSetWallClock_Option2 SV GPSSetWallClock_Option2 Set System Value Class name WALLCLOCKTIME Instance name Attribute Name DateTime Source GPS Year 2003 Page 26 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 4PPENDIX 8 RECOMMENDED PLC DATA
23. cast data Service A system feature that is performed on user demand Signal to noise ratio A measure of the relative power levels of a communication signal and noise on a data line SNR is expressed in decibels dB SV Space Vehicle GPS satellite Tag A named area of the controller s memory where data is stored like a variable Serer Me ere end of document P Page 41 of 41
24. ck on at least 4 satellites has been achieved the module s internal time will become valid Page 5 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 The current status of the module is conveyed to the user by means of the 3 bi color Status LED s and the alphanumeric LED display The following information is available to the user directly across the backplane by means of a scheduled connection Date and Time in Gregorian Format year month day hour minute etc Universal Coordinate Time UTC GPS Receiver Status Number of satellites being tracking Position in Polar Coordinates latitude longitude and altitude Position in Cartesian Coordinates Earth centered earth fixed X Y Z axis Velocity in Polar Coordinates Northerly Easterly and Upward Velocity in Cartesian Coordinates Earth centered earth fixed X Y Z axis The module requires regular updates of the ControlLogix Controller s CST Coordinate System Time value to enable accurate CST conversion and wall clock offset functions All time and date information can be adjusted to the local time zone by configuring the Time Zone offset in the scheduled output image Detailed GPS satellite information can also be requested by means of an unconnected message responding with the following for each of the 8 GPS receiver channels Satellite Identifier PRN Current Satellite Azimuth Current Satellite Elevation Signal Strength The 1756HP GPS IRIG OUT module supports two
25. ecific commands that enable the system to retrieve GPS satellite information as well as performing time base conversions These are accomplished using unconnected messaging via the MSG ladder instruction This enables communication to the module without a direct connection Appendix A and B provide example code and recommended data structures that can be used to store the information 7 1 Retrieving GPS Satellite Data The module provides tracking data for up to 8 satellites channels Information pertaining to each satellite includes PRN Each operational GPS satellite has a unique PRN identification number Elevation Measure of the elevation of the satellite in degrees from the horizon Azimuth Measure of the bearing to the satellite in degrees from true north SnR Measure of the satellite signal strength in dBHz calculated during signal correlation The information is requested by setting up a CIP Generic Custom message block The configuration of the message instruction is as follows Field Value Message Type CIP Generic Service Type Custom Service Code 0x32 Class 0x71 Instance 0x01 Attribute 0x01 Source Length 0 Destination Element Destination tag for reply data Table 7 1 Satellite data reguest configuration P Page 17 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 The message instruction will return the information in the following structure
26. ed The satellite masks used by the 1756HP GPS IRIG OUT receiver are listed in Table E 1 These masks serve as the screening criteria for satellites used in fix computations and ensure that position solutions meet a minimum level of accuracy The 1756HP GPS IRIG OUT receiver will only output position course speed and time when a satellite set can be acquired which meets all of the mask criteria Parameter Mask Elevation gt 5 SnR gt 3 PDOP 12 Table E 1 Satellite Mask Limits Elevation Mask Satellites below a 5 elevation are not used in the position solution Although low elevation satellites can contribute to a lower better PDOP the signals from low elevation satellites are poorer quality since they suffer greater tropospheric and ionospheric distortion than the signals from higher elevation satellites These signals travel further through the ionospheric and tropospheric layers In addition low elevation satellites can contribute to frequent constellation switches since the signals from these satellites are more easily obscured by buildings and terrain Constellation switches can cause noticeable jumps in the position output Since worldwide GPS satellite coverage is generally excellent it is not usually necessary to use satellites below a 5 elevation to improve GPS coverage time In some applications like urban environments a higher mask may be warranted to minimize the frequency of constellation switches
27. ing 4 satellites is sufficient to provide lock Valid CST 1 Module is receiving updates CST 0 Module has not received updated CST for 1sec or more Date Time Valid 0 Date Time Not Valid 1 Date Time synchronized with GPS Pulse per Second This bit transitions from 0 to 1 precisely every second The pulse duty cycle is approximately 50 Battery Backup on Boot 0 No battery backup available on boot up 1 Battery backup available on boot up With battery backup enabled the time taken for the GPS module to regain satellite lock is greatly reduced It is recommended that if the module is not to be used for an extended period that the battery backup be disabled Antenna OK 0 Antenna Fault 1 Antenna OK An Antenna fault will occur if the antenna is not present or has been damaged Local s I Data 0 16 Local s I Data 0 17 Local s I Data 0 18 Local s I Data 0 19 Local s I Data 0 20 Local s I Data 0 21 Local s I Data 0 22 BIT BIT BIT BIT BIT BIT BIT PDOP Ok West South PDOP OK 0 Position Dilution of Precision is unacceptable 1 No Position Dilution of Precision present Position Dilution of Precision occurs when although there are sufficient satellites in lock 2 or more of them appear to occupy similar positions in the sky and thus the number of effective satellites is decreased Current East West Hemisphere 0 Current position in East hemisphere
28. ites Cold Cold Initialisation Required Indicates that the module is devoid of internal satellite information Module will automatically download new almanac amp ephemeris data from a satellite Time Satellite Time synchronization in Progress Indicates that the module is receiving satellite signals but has not yet been able to synchronize to GPS time Lock Satellite Lock Indicates that sufficient satellites are being tracked to provide position fixing PDOP Position Dilution of Precision Warning Position Dilution of Precision occurs when although there are sufficient satellites in lock 2 or more of them appear to occupy similar positions in the sky and thus the number of effective satellites is decreased Page 24 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 Trk1 Tracking only 1 Satellite Trk2 Tracking only 2 Satellites Trk3 Tracking only 3 Satellites SBad Current Satellite is Bad The satellite signal currently being acquired is suspect or unusable SAT Satellite data request Module is processing a satellite data request C gt U Time Conversion CST gt UTC Module is performing a time conversion U gt G Time Conversion UTC gt Gregorian Module is performing a time conversion Page 25 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 A4PPENDIX A PLC LADDER EXAMPLE READ 1756HP GPS module into GPSlmage structure COP Copy File Source Local2 D
29. lite Ephemeris data changes hourly but is valid for up to four hours The GPS control segment updates the system almanac weekly and the ephemeris hourly through three ground based control stations During normal operation the 1756HP GPS IRIG OUT receiver module updates its ephemeris and almanac as needed The performance of a GPS receiver at power on is determined largely by the availability and accuracy of the satellite ephemeris data and the availability of a GPS system almanac P Page 32 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 D 2 Satellite Acguisition and Time to First Fix Cold Start The term cold start describes the performance of a GPS receiver at power on when no navigation data is available cold signifies that the receiver does not have a current almanac satellite ephemeris initial position or time The cold start search algorithm applies to a 1756HP GPS IRIG OUT receiver which has no memory of its previous session i e is powered on without the memory backup circuit connected to a source of DC power This is the out of the box condition of the GPS module as received from the factory In a cold start condition the receiver automatically selects a set of eight satellites and dedicates an individual tracking channel to each satellite to search the Doppler range frequency for each satellite in the set If none of the eight selected satellites is acquired after a predetermined period of time time out the
30. ped by the Tele Communication Working Group TCWG of the Inter Range Instrumentation group IRIG in October 1965 The latest IRIG standard is published in IRIG Standard 200 98 IRIG is a standard for transmitting time from one system to another for time synchronization purposes An IRIG master transmits an IRIG signal to multiply IRIG slaves on the network The IRIG signals consist of two words which together are exactly one second long The first word is the time of the year in binary coded decimal BCD with notation in seconds 7 Bits minutes 7 Bits hours 6 Bits and days 10 Bits The second word is called the Straight Binary Seconds SBS and is a binary counter of the number of seconds of the day which resets at midnight i e 0 to 86399 seconds Each IRIG consists of 10 sections Each section consists of 10 bits of 1mSec duration Each bit can have three values 1 0 and position identifier Po A 1 is set for 5mSec 0 for 2mSec and a position identifier is set for 8mSec as illustrated below G il 1 i il Pp 10m 10m 10m w gt mw gt SS ems 4 Sms Sl ms FIGURE A position identifier Po occurs between decimal digits in each group for visual separation An IRIG signal can either be transmitted as an amplitude modulated or DC level signal The amplitude modulated signal is modulated with a 1kHz sine wave Below is an illustration of both signal types The two reference bits as indicated below are the start of the IRIG
31. re CST Master Page 11 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 6 O ADDRESS MAP The input and output image of the 1756HP GPS IRIG OUT module is defined in the following sections Appendix A and B provide example code and recommended structures that can be used to extract and view the data 6 1 Input Image WORD 31 30 29 26 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 6 7 6 5 4 35 2 1 0 0 2 2 814 3 8 S z z AMEE Reserved a Sim A T j G 2 s Ola e 1 SY Count 2 Year 3 Month 4 Day 5 Hour 6 Minute T Second 8 Microsecond 9g UTC O 10 UTC 1 11 CST O 12 CST 1 13 CST Offset 0 14 CST Offset 1 Latitude Minutes nm Latitude Degrees Latitude Seconds al Longitude Minutes Longitude Degrees 18 19 20 21 22 23 24 25 26 ECEF Velocity X m s 27 28 ECEF Velocity Z m s Figure 6 1 Connected Input Image Page 12 of 41 4 1756HP GPS IRIG OUT User Manual Rev 2 6 6 2 Input Image Description Field Value Description Location Type Module OK GPS Locked CST Ok Time Valid PPS BATT Ok ANT Ok Module Status 0 Module has faulted 1 Module is operating properly Satellite Lock 0 Not tracking sufficient satellites to provide positional fix 1 Sufficient satellites being tracked to provide positional fix Typically track
32. receiver will select a new search set of eight satellites and will repeat the process until the first satellite is acquired As satellites are acquired the receiver automatically collects ephemeris and almanac data The Lassen SQ GPS receiver uses the knowledge gained from acquiring a specific satellite to eliminate other satellites those below the horizon from the search set This strategy speeds the acquisition of additional satellites required to achieve the first position fix The cold start search sets are established to ensure that at least three satellites are acquired within the first two time out periods As soon as three satellites are found the receiver will compute an initial position fix The typical time to first fix is less than 2 minutes A complete system almanac is not required to achieve a first position fix However the availability and accuracy of the satellite ephemeris data and the availability of a GPS almanac can substantially shorten the time to first fix Warm Start In a warm start condition the receiver has been powered down for at least one hour but has stored a current almanac an initial position and time in memory When connected to an external back up power source battery back up the 1756HP GPS IRIG OUT receiver retains the almanac approximate position and time to aid in satellite acquisition and reduce the time to first fix When an external back up battery is not used the TSIP protocol allows the almanac
33. rian date and UTC value Configuration of this message is illustrated below Message Configuration GPSConvertCSTMsg xj Configuration Communication Tag Message Type cdg Custom x Source Element GPSConvertCST CST ype Source Length fe Z Bytes Service i Cede 32 Hex Class 70 Hed Destination GPSConvetCST Ye x Instance h Attribute 1 Her s New Tag O Enable Enable Waiting D Start Done Done Length 48 Eror Code Extended Eror Code T Timed Out Eror Path GPS Eror Text ok Ceres Figure 7 2 Configuring the MSG CST gt UTC conversion reguest instruction Refer to Appendix A for code examples Field Value Message Type CIP Generic Service Type Custom Service Code 0x32 Class 0x70 Instance 0x01 Attribute 0x01 Source Length 0 Destination Element Destination tag for reply data Table 7 3 CST gt UTC conversion reguest configuration Page 19 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 The structure of the request is as follows Field Bytes Type Description CST 8 DINTI2 CST value Table 7 4 CST gt UTC conversion request data A successful conversion will result in the following response Field Bytes Type Description Year 2 DINT Gregorian year Month 2 DINT Gregorian month Day 2 DINT Gregorian day Hour 2 DINT Grego
34. rian hour Min 2 DINT Gregorian min Sec 2 DINT Gregorian sec uSec 2 DINT Gregorian uSec UTC 8 DINT 2 Corresponding UTC value CST 8 DINT 2 Given CST value Table 7 5 CST gt UTC conversion successful response data An unsuccessful response code 0x03 will be sent back should the CST not fall within the previous logged hour Error Code Description 0x02 CST Value requested for conversion is in the future 0x03 CST Value requested for conversion is in the too far in the past greater than 1 hour 0x04 Unable to find match due to possible invalid time occurring during logging Page 20 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 7 4 Converting UTC to Gregorian Time By supplying the full 64 bit UTC value the module will return the corresponding full Gregorian date Configuration of this message is illustrated below Message Configuration GPSConvertUTCMsg ii x Configuration Communication Tag Message Type ae Custom Source Element GPSConverUTC UT x ype Source Length fe H Bytes Service 33 3 70 Code 33 Hex Class 70 Hex Destination GPs ConvertUTC Ye Instance f Attribute f1 Hes New Tag O Enable Enable Waiting Start Done Done Length 0 Eror Code Extended Emor Code J Timed Out Eror Path Eror Text ok Ceres Figure 7 3 Configuring the MSG UTC gt Gregorian conversion request instruction The message instr
35. s x 10 The X axis is defined as the vector with origin at the earth s centre and passing through the intersection of the equator and Greenwich meridian Speed with respect to the Y axis m s x 10 The Y axis is defined as the vector with origin at the earth s centre and passing through the equator 90 degrees east of the Greenwich meridian Speed with respect to the Z axis m s x 10 The Z axis is defined as the vector with origin at the earth s centre and passing through the North pole Local s 1 Data 24 Local s I Data 25 Local s I Data 26 Local s I Data 27 Local s I Data 28 REAL REAL REAL REAL REAL Page 15 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 Output Image Reserved Reserved Timezone 6 4 Output Image Description Field Description Location Type Reserved Reserved 64Bits 64BIT Time Zone Configuration Used to set the module to report in local time standard Time zone Time zone UTC Offset where the UTC Offset is the Local s 0 Data 2 REAL difference in hours between local time and GMT E g For Pacific Standard Time GMT 8 set time zone 8 The Time zone needs to be copied from a tag of type real into the output word Appendix A and B provide example code and recommended data types Page 16 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 7 MODULE SPECIFIC COMMANDS The 1756HP GPS IRIG OUT module offers sp
36. sed See Appendix B P Page 37 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 E 4 Coordinate System Time CST The CST Coordinated System Time is a 64 bit count of the number of microsecond ticks from some arbitrary instance This value is generated by the CST master and supplied to all other modules in the rack Only one of the modules usually the CPU in the ControlLogix rack can be configured to be the CST Master at any given time E 5 Wall Clock Time WCT and CST Offset The wall clock object located in the ControlLogix CPU maintains the conversion of the CST value to a value that is relative to a system defined point in time This allows the user to set the Wall Clock to coincide with local or any other time standard WCT is derived from the CST by adding an offset known as the CST Offset WCT CST CST Offset The 1756HP GPS IRIG OUT module calculates the required CST Offset in order to set the WCT to UTC time or local time depending on the configured Time Zone TimeZone GPS Time GPS UTC Offset a gt al 2 gt gt Local Time wet SSV UTC gt lest Ofset wet orfsett gt SSV f Oo A GSV 1756HP GPS ControlLogix CPU Page 38 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 Figure F 1 Time Standard Relationship 4PPENIXF IRIG STANDARD IRIG was develo
37. tion Satellite sets which are tightly clustered or aligned in the sky will have a high DOP and will contribute to a lower position accuracy For most applications a DOP mask of 12 offers a satisfactory trade off between accuracy and GPS coverage time Position Accuracy GPS position accuracy is degraded by atmospheric distortion satellite geometry satellite clock errors and receiver clock errors Effective models for atmospheric distortion of satellite signals have been developed to minimize the impact of tropospheric and ionospheric effects The impact of satellite clock errors is minimized by incorporating the clock corrections transmitted by each satellite used in the position solution GPS Timing In many timing applications such as time frequency standards site synchronization systems and event measurement systems GPS receivers are used to discipline local oscillators The GPS constellation consists of 24 orbiting satellites Each GPS satellite contains a highly stable atomic Cesium clock which is continuously monitored and corrected by the GPS control segment Consequently the GPS constellation can be considered a set of 24 orbiting clocks with worldwide 24 hour coverage GPS receivers use the signals from these GPS clocks to correct its internal clock which is not as stable or accurate as the GPS atomic clocks GPS receivers like the 1756HP GPS IRIG OUT s receiver output a highly accurate timing pulse PPS generated by its
38. uction should be configured as follows Field Value Message Type CIP Generic Service Type Custom Service Code 0x33 Class 0x70 Instance 0x01 Attribute 0x01 Source Element Tag containing requested UTC value Source Length 8 Destination Element Destination tag for reply data Table 7 6 UTC gt Gregorian conversion request configuration 4 Page 21 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 The structure of the request is as follows Field Bytes Type Description UTC 8 DINT 2 UTC value Table 7 7 UTC gt Gregorian conversion response data A successful conversion will result in the following response Field Bytes Type Description Year 2 DINT Gregorian year Month 2 DINT Gregorian month Day 2 DINT Gregorian day Hour 2 DINT Gregorian hour Min 2 DINT Gregorian min Sec 2 DINT Gregorian sec uSec 2 DINT Gregorian uSec UTC 8 DINT 2 Corresponding UTC value Table 7 8 UTC gt Gregorian conversion successful response data An unsuccessful response will be sent back should the UTC not fall within the previous logged hour Error Code Description 0x02 UTC Value requested for conversion is in the future 0x03 UTC Value requested for conversion is in the too far in the past greater than 1 hour 0x04 Unable to find match due to possible invalid time occurring d
39. umbered by adverse weather In addition the accuracy of Loran navigation varies with geographic location and even under ideal conditions cannot compare with GPS By computing the distance to GPS satellites orbiting the earth a GPS receiver can calculate an accurate position This process is called satellite ranging A 2D position calculation requires three satellite ranges A 3D position calculation which includes altitude requires four satellite ranges GPS receivers can also provide precise time speed and course measurements which are beneficial for vehicle navigation D 1 GPS Satellite Message Every GPS satellite transmits the Coarse Acquisition C A code and satellite data modulated onto the L1 carrier frequency 1575 42 MHz The satellite data transmitted by each satellite includes a satellite almanac for the entire GPS system its own satellite ephemeris and its own clock correction The satellite data is transmitted in 30 second frames Each frame contains the clock correction and ephemeris for that specific satellite and two pages of the 50 page GPS system almanac The almanac is repeated every 12 5 minutes The ephemeris is repeated every 30 seconds The system almanac contains information about each of the satellites in the constellation ionospheric data and special system messages The GPS system almanac is updated weekly and is typically valid for months The ephemeris contains detailed orbital information for a specific satel
40. uring logging Page 22 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 CHAPTER 8 MODULE STATUS The following sections describe the various statuses of the module and how they may be determined via the 3 bi color Green Red LED s and the message on the display 8 1 Status LED s LED DESCRIPTION STATUS MEANING Solid Red Major Hardware Fault OK Module Status Flashing Red Major Fault Flashing Green Minor Fault Green Module operating correctly Solid Red Antenna Failure Flashing Red No Satellite found LOC GPS Lock Status Flashing Green Busy acquiring satellites Green Full GPS Lock positioning and time fixing Solid Red No PPS available PPS Pulse Per Second Flashing Red Premature PPS before lock Flashing Green Normal Synchronized to GPS Time Table 8 1 LED status information of the module Page 23 of 41 1756HP GPS IRIG OUT User Manual Rev 2 6 8 2 Status Display Init Initialization of Module The module is initialized only on power up Frn Firmware Revision The firmware revision number is displayed on power up AntO Antenna Open Circuit Indicates the Antenna is not connected or damaged Sky No Sky Available Indicates the absence of any satellite signals This usually occurs when the Antenna is placed indoors or during power up before Lock is achieved Srch Satellite Search Module is attempting to acguire satell
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