 SatStat Help

Normal Operation

Overview/Getting Started

Main Form

Control & Query Form

Communication Settings Form

Specialized Uses

Demo Mode

Downloading Firmware

RECEIVER.INI File

To learn how to use Help, press F1.


 Normal Operation: Overview

This application provides status information and direct control & query capability for the features of the following Symmetricom GPS Timing Receiver products: 55300A, 58503B, and 59551A.

When the application is started, two forms appear.  The larger form provides continual status updates, displaying the output from the SYST:STAT? query, which is repetitively sent to the timing receiver.  To get this working, you'll need to establish communication with the timing receiver via the appropriate port on your PC.  Use the CommPort->Settings selection to bring up the Communication Settings Form.  All of the settings have been preset to be appropriate for the timing receiver, except for the Com Port selection, which will be based on your particular setup.  (see Communication Setup)

Once you think the communication settings are correct, open the communication port using the CommPort->Port Open selection.  When the port is open, this selection will have a check mark.  Once the port is opened, timing receiver status information should begin to appear on the large form.  If updates don't occur, observe the status area (just below the menu selections).  If there is no communication with the timing receiver, the message "Trying to establish communication" will appear.  Solving this problem is beyond the scope of this description, but some of the most likely causes are: wrong Com port selected on the PC, you may have changed some other setting on the communications settings form (you don't need to), the RS-232 cable isn't connected to either the PC or the timing receiver, or your cable may need a null modem adapter.  If you are trying to fix a communication problem, you don't need to shut down this program, it will just keep trying to communicate with the timing receiver (as long as you have Port Open selected) and, if it ever succeeds, the status information will automatically appear on the large form.  See the getting started guide that came with your GPS receiver for more troubleshooting help.


 Normal Operation: Main Form

Click on the part of the Form you want to know more about:

 The Receiver Status Screen provides a comprehensive summary of the key operation conditions and settings.  It is comprised of 23 lines of formatted text, with a maximum of 79 characters per line.  Receiver functionality is viewed and categorized into three process blocks: Synchronization, Acquisition, and Health Monitor.  The operational state of each process is summarized by an advisory message that follows the title of each segment.


 Normal Operation: Control & Query Form

Click on the part of the Form you want to know more about:

 The primary function of this form is to provide you with a mechanism for controlling and viewing various conditions within the GPS Timing Receiver.  You can use the Control and Query menus to provide quick access to commonly used selections, or can directly type the desired command/query in the edit area.  Detailed command information is provided in the Operating and Programming Manual or is available on a single "at a glance" document.


Normal Operation: Communication Setup
 Normal Operation: Communication Settings Form

Click on the Form for more info:

 This form is accessed from the Main Form via the CommPort Menu by selecting Settings... .  It is important that you select settings that match the settings of the GPS Timing Receiver.  The default settings for this application have been set to match the default settings for the GPS Timing Receiver.  The only setting you'll likely need to set is the Com Port setting, although COM1 is often correct.  The selection you make here will be stored when you exit the application, and will be recalled the next time you start it up, so that you won't have to go through setting up this form every time.  Once you've completed your selection, use the OK button to exit.


 Specialized Uses: Demo Mode

Demo mode is provided to allow you to get some idea of how this application works when you don't actually have a Symmetricom GPS Timing Receiver connected.  Use the Function menu on the main form to select Demo Mode.  Once selected, the Status and Clock functions will both simulate real behavior by updating their time (and date) information using the PC clock.  Of course, the timing information will then be only as accurate as your PC clock.


 Specialized Uses: Downloading Firmware

Click on the part of the Form you want to know more about:

 This form is accessed from the Control & Query Form via the Service Menu by selecting Download Firmware... .  The purpose of this form is to provide a means of updating firmware in the Symmetricom GPS Timing Receiver.  You would only use this feature if Symmetricom has provided you with a downloadable firmware file and instructions that you should perform a download.  When this form is on-screen, none of the other forms can be accessed.  To re-gain access to other forms, you must first close this one.

CAUTION: Although you are always asked to confirm that you want to actually download even after you initially request it, you should be careful not to attempt this unless instructed to do so.  Since the process begins with erasure of the current firmware, you will lose the current firmware if you attempt a download without actually having a new version to download.


 Initialization Information

To save you the trouble of having to constantly reset application parameters each time you start up this application, many of them are saved in an initialization file whenever you close the application.  This way, they can be restored each time you restart the application.  If you terminate the application in an abnormal way (e.g., turn off your PC), the settings won't be updated in the initialization file.  This file is called receiver.ini and can be found in the windows directory (it will only exist after you've run the application once).

The information that is saved includes: all of the communication settings (see Communication Setup), the font selections for the Status and Clock functions, and the Function selection (either Status or Clock).


 Glossary

Term	Definition

Elevation Mask	The receiver considers for tracking those satellites with predicted elevation angles at or above the Elevation Mask setting.
FFOM	Frequency Figure of Merit, a number between 0 and 3: 0 indicates that the output is stable (locked), 1 indicates that the output is stabilizing (locked), 2 indicates that the unit is unlocked and in holdover, 3 indicates that the unit is unlocked but not in holdover (e.g., still in initial power-up).
GPS	Global Positioning System: a satellite-based system for navigation and timing.
Holdover	GPS Timing Receiver mode of operation entered into when GPS lock is lost.  Holdover makes use of learned oscillator characteristics while timed to GPS.
Locked	GPS Timing Receiver mode of operation where timing is controlled by received GPS signal.
OCXO	Oven Controlled Crystal Oscillator: quartz oscillator housed in an oven to maintain stable temperature for enhanced oscillator performance.
PC	Personal computer.
PPS	Pulse Per Second: One of signals the GPS Timing Receiver produces is a 1 PPS signal.
PRN	The pseudorandom noise code of the satellite.  Code numbers 1 through 32 are assigned to orbiting satellites; codes 33 through 37 identify ground-based GPS transmitters.
RS-232	Serial communication used between the computer and GPS Timing Receiver.
SmartClock	A collection of algorithms to improve timing receiver performance, both in locked and holdover operation, by learning and compensating for oscillator characterstics.
S-record	A section of firmware download data.
SS	The relative signal strength of the satellite, which is proportional to the signal-to-noise ratio of the received signal.  The maximum SS value is 255; 20 to 30 is the minimum range for stable tracking.
Survey	GPS Timing Receiver determination of position, typically conducted when a receiver is initially powered up.
TFOM	Time Figure of Merit: a number between 0 (best) and 9 (worst) that indicates the accuracy of the 1PPS Output.
UTC	Universal Coordinated Time: time scale that is the basis for international time and frequency standards.


Main Form: File Menu

Use this menu to close the application.  The only choice is Exit.


Main Form: Edit Menu

The only choice on this menu is Copy to Clipboard.  Use this selection to copy the entire displayed status information on the large form to the clipboard.  You can use the Windows Clipboard Viewer to see what has been copied.  Once copied to the clipboard, this status information can be pasted into various other applications, such as a word processor.


Main Form: CommPort Menu

Use the Port Open selection on this menu to enable communication between your PC and the timing receiver.  When the port is open (i.e., communication will be attempted), this menu entry will be checked.  The application always starts up with the port not open (unchecked).

Use the Settings... selection to bring up the communication settings form.  When this software is initially run, all settings should be properly preset for the timing receiver (assuming its communication settings haven't been re-programmed), except for the Com Port setting, which will be dependent on how you've configured your PC.  The Settings you select on the communication settings form will be saved when you exit the application.  Then next time you run the application, these settings will be recalled for you (see Communication Setup).


Main Form: Function Menu

The Status and Clock choices on this menu allow you to select either an updating comprehensive status screen, which shows many aspects of receiver operation, or an updating form that shows time of day.  Although the Status selection also shows time of day, because it is only updated about once every second, whereas the Clock selection is updated numerous times per second, you should select Clock if you are mostly interested in an accurate time display.  You can control font styles for both Status and Clock Functions.  The Status/Clock setting is saved when you close the application, so that it will start up with your preference the next time you run this application.

The Disable Updates selection provides a way to stop the repeated updates of either the Status or Clock displays.  This selection toggles; selecting it when unchecked will check it (stopping the update process), selecting it when checked will uncheck it (re-initiating the update process).

Demo Mode provides a way to have either the Status or Clock displays updated even when there is no GPS Timing Receiver connected.  The time information is updated on either display using an available clock within the PC, no fields are updated on the Status display.  When Demo Mode is selected, the title on the main form will indicate that this is only a demo.  The time information provided in Demo Mode is only as accurate as the clock setting on your PC.


Main Form: Style Menu

The Style Menu allows you to customize the font characteristics of either the Status or Clock display, depending on the function selection.  These settings are saved when you exit the application and are recalled the next time you start this application.

Status Font... brings up a form that explains setting of status screen font information.  From this form, you can access a form that allows full selection of fonts, sizes, and other attributes.  As mentioned on the font information form, only non-proportionally spaced fonts work well with the status display.

Clock Font... brings up a form that explains setting of clock screen font information.  This form provides the means for enlarging or reducing the font size, while access is provided to another form that allows you to select the font itself and other attributes.


Main Form: Help Menu

Provides access to this help information.


Main Form: Received Status

This area provides continual feedback about what the application is doing.  Think of it as an activity indicator: when there are lots of things going on, you may not be able to read each message, but when there is a problem, such as lack of communication to the timing receiver, the feedback provided here will be helpful.


Main Form: Synchronization Area

The synchronization area shows the receiver's current operating mode, indicated by >>:

Locked to GPS : frequency is stable

                           : stabilizing frequency

1 PPS Output is locked, and the frequency stability is high or degraded, respectively.  The SmartClock algorithm is learning the characteristics of the OCXO.

Recovery

Locking to GPS 1 PPS CLK signal

Holdover :GPS 1PPS CLK inaccurate

                 :1PPS TI exceeds hold threshold

                 :manually initiated

                 :internal hardware problem

Not locked due to the condition indicated; the SmartClock algorithm is applying learned characteristics to improve the accuracy of the OCXO.

Power-up

The OCXO is warming up, and its frequency is being measured and adjusted.

Holdover Duration reports the duration of Holdover and Recovery operation.


Main Form: GPS Reference Area

Reference Outputs lists measures of time and frequency accuracy:

TFOM:	Time Figure of Merit: a number between 0 (best) and 9 (worst) that indicates the accuracy of the 1PPS Output, defines as log (delta T/T) + 9.  For example, 3 - which is the minimum TFOM value - represents a maximum timing error of between 100 and 1000 nanoseconds.

FFOM:	Frequency Figure of Merit, a number between 0 and 3: 0 indicates that the output is stable (locked), 1 indicates that the output is stabilizing (locked), 2 indicates that the unit is unlocked and in holdover, 3 indicates that the unit is unlocked but not in holdover (e.g., still in initial power-up)

1PPS TI: Average phase difference between SmartClock 1PPS and GPS 1PPS timing signals.

HOLD THR: 1PPS phase difference threshold; while exceeded, holdover operation is maintained.


Main Form: Acquisition Area/Tracking

The Tracking table identifies satellites currently tracked by the receiver. Up to six satellites can be tracked  concurrently.  The receiver attempts to track satellites highest above the horizon.  One or more satellites must be tracked to generate an accurate GPS 1PPS CLK signal.  Four or more satellites must be tracked to survey position.

PRN: The pseudorandom noise code of the satellite.  Code numbers 1 through 32 are assigned to orbiting satellites; codes 33 through 37 identify ground-based GPS transmitters.  Satellites are sorted by ascending PRN's.

El: The predicted elevation of the satellite, in degrees, derived from almanac data.  "--" denotes it is unknown, such as when the satellite is not predicted to be visible but is selected by the receiver's "sky search" algorithm.

Az: The predicted azimuth of the satellite (degrees), referenced to true north, derived from almanac data; "--" if unknown.

SS: The relative signal strength of the satellite, which is proportional to the signal-to-noise ratio of the received signal.  The maximum SS value is 255; 20 to 30 is the minimum range for stable tracking.

The receiver considers for tracking those satellites with predicted elevation angles at or above the setting ELEV MASK.


Main Form: Time Area

Time maintained by the GPS engine, which defaults at powerup to 12:00:00, January 1.  This setting will be corrected with the time obtained from any satellite.

UTC: Coordinated Universal Time

GPS: GPS Time = UTC - accumulated_leapseconds

LOCAL UTC: UTC, offset to local time zone

LOCAL GPS: GPS Time, with local offset


Main Form: 1PPS Area

1PPS CLK reports the validity of the 1PPS signal generated by the GPS engine.  Precise time and position are required for accurate time transfer.

Synchronized to UTC (or GPS Time):  GPS 1PPS signal is reported accurate

Assessing stability . . .:  1PPS must be accurate for 30 seconds

Inaccurate: not tracking:  One or more satellites must be tracked

Inaccurate: no position:  Position has not been surveyed

Absent or freq incorrect: Engine is idle, or a hardware problem

ANT DLY is an offset of the GPS 1PPS signal to compensate for antenna system delay.


Main Form: Position Area

Position of the GPS antenna must be precisely known for accurate 1PPS timing.  Two position MODE conditions are provided: Hold, for direct entry; and Survey, where position is computed form pseudo-range measurements.  In Survey mode, the receiver averages 7200 position calculations and invokes position Hold at the averaged coordinates.  If surveying is suspended, one of two advisory messages is reported:

Suspended: track <4 sats:  Pseudo-range measurement requires four or more satellites with good geometry.

Suspended: poor geometry:  Dilution of precision is too large for an accurate pseudo-range measurement.

Specifying an approximate INITial position and time will significantly reduce acquisition time by narrowing the search window for a satellite's C/A code sequence.


Main Form: Health Monitor

The OK summary message at the end of the Health Monitor line indicates that no errors or failures were detected.  Error indicates that one or more hardware tests failed.  For each hardware function, OK is reported when it is operating normally; Err is displayed when a failure or an error is detected.  Hardware functions are monitored periodically, with the exception of Self Test, which is performed at power-up or when requested.


Control & Query Form: Edit Menu

The Edit Menu has a single selection: Copy to Clipboard.  Use this selection to copy the entire contents of the scrollable text box that appears just below the menu selections.  This information can then be pasted into other applications.  You can view the copied information in the Windows Clipboard Viewer or paste it into other applications, such as a word processor.


Control & Query Form: Control Menu

The Control Menu provides quick access to many of the settable parameters in the timing receiver.  When one of the entries is selected, the command form for that parameter will appear in the entry box (just below the scrollable text box) along with an explanation of what the parameter does and what entry you need to provide (the explanation appears just below the entry box).  To actually change the value of the selected parameter, enter the value(s) that are desired, then select the Send Cmd button or press the Enter key.  Either way, the command will be sent.  A message will appear in the scrollable text box indicating that your command has been sent.  After a few seconds, a response message will appear, indicating how your command has fared.  The possible responses are: command complete (indicating that the command has been successfully accepted by the timing receiver), No Response from Unit (indicating that there was no communication with the timing receiver), or an error number with explanation will appear (indicating that the command was unacceptable for the displayed reason).  For most selections, there will be a corresponding change in the status information on the main form as a consequence of the parameter change.

After you've changed a given parameter, you don't have to re-select it from the Control menu the next time you want to make a change.  The command entry box keeps a list of commands you have used.  You can access this list from the down-arrow button at the far right of this control or by using the up or down arrow keys on the keyboard to scroll through prior selections.  Once you've made a choice, you can then edit the entry as appropriate.

The bottom selection on this menu, Alarm Clear, can be used to immediately clear an alarm an display the reason why the alarm was on.  This information will appear in the response area just below menu selections on this form.  Unlike the other commands on this menu, when you select Alarm Clear->Clear alarm and show cause, the action will occur immediately.

The selections found on the Control menu are dependent on the product you are using.


Control & Query Form: Query Menu

The Query Menu provides a quick access to status of numerous timing receiver parameters.  When one of these entries is selected, the command to query for that parameter will appear in the entry box (just below the scrollable text box) along with an explanation of what the parameter does.  To actually query the value of the selected parameter, select the Send Cmd button or press the Enter Key.  Either way, the command will be sent.  A message will appear in the scrollable text box indicating that your command has been sent.  After a few seconds, a response message will appear, indicating how your command has fared.  The possible responses are: command complete (indicating that the query has been successfully accepted by the timing receiver), No Response from Unit (indicating that there was no communication with the timing receiver), or an error number with explanation will appear (indicating that the query was unacceptable for the displayed reason).

After you've queried a given parameter, you don't have to re-select it from the Query menu the next time you want to make query it.  The command entry box keeps a list of commands you have used.  You can access this list from the down-arrow button at the far right of this control or by using the up or down arrow keys on the keyboard to scroll through prior selections.  Once you've made a choice, you can then edit the entry as appropriate.

The selections found on the Query menu are dependent on the product you are using.


Control & Query Form: Service Menu

The Service Menu provides access to the Download Firmware...selection, which is used when the firmware that operates the GPS Timing Receiver needs to be updated.


Control & Query Form: Help Menu

Provides access to this help information.


Control & Query Form: Clear Button

Use this button to clear out the scrollable region to the left.  You might do this before beginning a session where you intend to save the responses.  Note that when you're done, you can copy the scrollable region to the clipboard using Edit->Copy to Clipboard.


Control & Query Form: Send Command Button

Use this button to send a command or query to the GPS Timing Receiver.  The command/query sent will be whatever is entered in the edit region just to the left of this button.  If you prefer, you can use the enter key to send the command instead of this button.  While the command is being processed, this button will be disabled (gray), to indicate that anoher command can't yet be sent.


Control & Query Form: Clear Command Button

Use this button to clear out the command/query entry area to the left of this button.  You might use this before typing in a new command.


Control & Query Form: Response Area

The scrollable text box on the Control & Query form provides a log of all user-initiated communications with the timing receiver.  Use the vertical scroll bar to scan through prior communications that you initiated with the timing receiver.  If for any reason you want to clear out this log, use the <--Clear button just to the right of the communication log.  One reason for doing this would be just prior to performing a Copy to Clipboard (see Edit menu), to isolate a particular piece of information to copy.


Control & Query Form: Command/Query Entry Area

Use the command entry box (the lower-most text entry control on this form) to send commands to the timing receiver.  You can access pre-selected commands from the Control or Query menus, or you can directly enter any command here by using standard edit methods.  For pre-selection commands, a brief explanation of what the command does is provided below the command entry area.  When you're ready to send the command, select the Send Cmd button or press the enter key.  An indication that you have attempted to send the command will appear in the Communication Log, just above this entry form.

After you've sent a command, you can re-access it from a history list that is updated with each new command.  You can access this list from the down-arrow button at the far right of this control, or by using the up or down arrow keys on the keyboard to scroll through prior selections.  Once you've made a choice, you can send it to the timing receiver, or edit if first and then send it.

Use the Clear Cmd button to clear a command that appears in the entry area.


Communications Settings Form: RS-232 Settings
Communication Settings Form: RS-232 Settings

This form is used to select appropriate communication settings for the RS-232 (serial) port that you're using to communicate with the GPS Timing Receiver.


Firmware Download Form: Selected File

The file that you've selected for download should appear in this area.  You can either type the filename directly or use the File... button to browse for the proper file to download.


Firmware Download Form: File Button

Select this button to choose the file that you will use for the download.  When selected, a form will appear that allows access to all drives (and files on them) that are available to your PC.  After selection of the file, its name and path will appear in the File to Download display area.


Firmware Download Form: Download Button

Selecting this button initiates the actual firmware downloading process.  You will first be asked to confirm that this is really what you want to do.  If you choose to proceed, the flash memory will be erased, and the file records will be sent to the GPS Timing Receiver.  Other displays on this form will allow you to observe the progress of the download.


Firmware Download Form: Close Button

Use this button to close this form.  While the download is progressing, this button won't be available (grayed out).  During the download, a button will appear just to the left of the Close button, which will say Stop Download.  You can use that button to terminate the download at any time.


Firmware Download Form: Lines Sent

As the download proceeds, this area will identify the number of S-records that have been sent to the GPS Timing Receiver.


Firmware Download Form: Lines Retried

Occasionally, during a download, an S-record will fail to program properly.  When this happens, it will be resent, generally with a successful outcome.  This area will accumulate the total number of re-tries that have occurred during the download process.  A non-zero value does not mean that anything is wrong.  If an S-record can't be programmed successfully, it will be repeatedly retried until it either becomes successful or eventually a form will appear indicating that an excessive number of errors have occurred.


Firmware Download Form: Activity Indicator

While the download is taking place, this area will show you the individual S-records that are being sent to the GPS Timing Receiver.  Think of it as an activity indicator, since you won't have time to observe each record in detail.