NAVSYNC CW25 User manual

CW25 GPS
Receiver
User Manual
Issue: R03
Bulletin NS15-UM
Revision 03
Date 16 June 2008

CW25 Software User Manual Page 2 of 50 Rev 03 Date: 06/16/08
Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
1. DESCRIPTION .............................................................................................................................................................. 4-6
1.1 Introduction...................................................................................................................................................4
1.2 Global Positioning System ...........................................................................................................................5
1.3 GPS Positioning and Navitation ..................................................................................................................5
1.4 Standard Positioning Service (SPS)............................................................................................................6
1.5 Precise Positioning Service (PPS) ..............................................................................................................6
2.SPECIFICATION ............................................................................................................................................................ 7-8
2.1 Performance .................................................................................................................................................7
2.2 Recommended Ratings ...............................................................................................................................7
2.3 Absolute Maximum Ratings.........................................................................................................................8
2.4 Block Diagram ..............................................................................................................................................8
3. PHYSICAL CHARACTERISTICS............................................................................................................................... 9-10
3.1 Physical Interface Details ............................................................................................................................9
3.2 MCM Dimensions...................................................................................................................................... 10
3.3 Solder Pad Size and Placement .............................................................................................................. 10
4. SIGNAL DESCRIPTION............................................................................................................................................ 11-14
4.1 Power Signals ........................................................................................................................................... 11
4.2 RF Signals ................................................................................................................................................. 12
4.3 Emulation/Test Signals ............................................................................................................................. 12
4.4 Control Signals.......................................................................................................................................... 13
4.5 I/O Signals ............................................................................................................................................ 13-14
5. FEATURES..................................................................................................................................................................... 15
5.1 Power on Reset ......................................................................................................................................... 15
5.2 Time Transfer ............................................................................................................................................. 15
5.3 CW25 Embedded Identification................................................................................................................ 15
5.4 Build Options ............................................................................................................................................. 15
6.OPERATING MODES...................................................................................................................................................... 16
6.1 Stand Alone Operation ............................................................................................................................. 16
6.2 Net Assisted Operation ............................................................................................................................. 16
7. POWER MANAGEMENT ............................................................................................................................................... 16
7.1 Coma Mode............................................................................................................................................... 16
8. COMMUNICATIONS PROTOCOLS.......................................................................................................................... 17-30
8.1 Port Configurations ................................................................................................................................... 17
8.2 Output Format....................................................................................................................................... 17-24
8.2.1 NMEA Messages ............................................................................................................................. 17
8.2.1.1 GPGLL - Geographic position, Lat/Lon ................................................................................... 17
8.2.1.2 GPGGA - GPS fix data.............................................................................................................. 18
8.2.1.3 GPGSA - GPS DOP and Active satellites ................................................................................ 18
8.2.1.4 GPGSV - GPS Satellites in View .............................................................................................. 19
8.2.1.5 GPRMC - Recommended Minimum data................................................................................ 19
8.2.1.6 PVTG - Course over ground and Ground speed. ................................................................... 20
8.2.1.7 GPZDA - UTC Time and Date .................................................................................................. 20
8.2.1.8 POLYT - Time of Day................................................................................................................. 20
8.2.1.9 POLYP- Position Data............................................................................................................... 21
8.2.1.10 POLYS - Satellite Status ......................................................................................................... 22
8.2.1.11 POLYI, Additional Information Message ................................................................................ 22
8.2.2 Debug Messages........................................................................................................................ 23-24
8.2.2.1 Navigation and Timing Summary ($11) .................................................................................. 23
8.2.2.2 RF & AGC data ($52)................................................................................................................ 24
TABLE OF CONTENTS

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CW25 Software User Manual Page 3 of 50 Rev 03 Date: 06/16/08
8.3 Command Format * .............................................................................................................................. 25-29
8.3.1 PRTH<Q|R>, VERS: Software Version ............................................................................................ 25
8.3.2 PRTH<Q|S|R>, DYNA: RECEIVER DYNAMICS............................................................................. 26
8.3.3 PRTH<Q|S|R>, ITIM: INITIALISE TIME AND DATE ........................................................................ 26
8.3.4 PRTH<Q|S|R>, RSET: RE-SET THE RECEIVER ........................................................................... 27
8.3.5 PRTH<Q|S|R>, INTM:INTERMITTENT OPERATION PARAMETERS............................................ 27
8.3.6 PRTH<Q|S|R>, ILLH: INITIALIZED LAT, LONG, HEIGHT POSITION............................................. 28
8.3.7 PRTH<Q|S|R>, COMA: COMA MODE ............................................................................................. 28
8.3.8 PRTH<Q|S|R>, FRQD: FREQUENCY OUTPUT SELECT .............................................................. 28
8.3.9 PRTH<Q|S|R>, MMSV:MIN & MAX SATELLITES FOR A POSITION SOLUTION ......................... 29
8.3.10 PRTH<Q|S|R>, DRLM: DEAD RECKONING LIMIT ...................................................................... 29
8.3.11 PRTH<Q|S|R>, ELVM: SATELLITE ELEVATION MASK ................................................................ 29
8.4 Network Assistance Input ......................................................................................................................... 30
8.4.1 Message Definition .......................................................................................................................... 30
9. NMEA and UART Configuration Details................................................................................................................. 31-32
9.1 NMEA Configuration Query ($PRTHQ, UxOP): ....................................................................................... 31
9.2 NMEA Configuration Set ($PRTHS,UxOP): ............................................................................................. 31
9.3 UART Configuration Query ($PRTHQ, UxCM): ....................................................................................... 32
9.4 UART Configuration Set ($PRTHQ,UxCM) .............................................................................................. 32
10. LED INTERFACE ......................................................................................................................................................... 32
11. ILD NETWORK ASSIST MESSAGE FORMAT....................................................................................................... 33-39
11.1 Message Definitions .................................................................................................................... 34-39
11.1.1 #EPH, Ephemeris Sub frame Message.................................................................................... 34
11.1.2 #ALM, Almanac Subframe Message ........................................................................................ 34
11.1.3 #KLB, Klobuchar Ionospheric Parameters Message.............................................................. 35
11.1.4 #UCP, UTC Correction Parameters Message .......................................................................... 35
11.1.5 #TIM, Time Input Message ........................................................................................................ 36
11.1.6 #LOC, Location Message ......................................................................................................... 36
11.1.7 Example Sequence Of Messages ....................................................................................... 37-39
12.TIME PULSE INTERFACE ........................................................................................................................................... 40
13. FREQUENCY OUTPUT ............................................................................................................................................... 40
14. APPLICATION HINTS ............................................................................................................................................. 41-43
14.1 Power Supply .................................................................................................................................... 41
14.2 RF Connection .................................................................................................................................. 41
14.3 Grounding ......................................................................................................................................... 42
14.4 Battery Backup .................................................................................................................................. 42
14.5 Over Voltage & Reverse Polarity Protection ..................................................................................... 43
14.6 Reset Generation .............................................................................................................................. 43
14.7 Boot Options...................................................................................................................................... 43
14.7.1 Flash Programming ................................................................................................................... 43
APPENDIX 1 ................................................................................................................................................................. 44-46
Glossary ............................................................................................................................................... 44-46
APPENDIX 2 ...................................................................................................................................................................... 47
Contact Details .......................................................................................................................................... 47
APPENDIX 3 ...................................................................................................................................................................... 47
World Wide Web Information .................................................................................................................... 47
APPENDIX 4 ...................................................................................................................................................................... 48
Tape & Reel Specifications ....................................................................................................................... 48
Solder Profile............................................................................................................................................. 48
TABLE OF CONTENTS

CW25 Software User Manual Page 4 of 50 Rev 03 Date: 06/16/08
Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
1. DESCRIPTION
1.1 Introduction
The CW25 GPS receiver (CW25) is a small size GPS OEM module that has been specifically designed for use in weak
signal GPS environments and for rapid integration into host systems, while maintaining all the features of a standard GPS
solution, such as high accuracy.
Normal GPS systems cannot track satellites below –176 dBW (-146 dBm) however the CW25 can track down a further
10 dB resulting in tracking down to –186 dBW (-156 dBm).This makes it possible to track the person, asset or vehicle as
they enter buildings, move under dense vegetation, or drive through dense urban canyons. Furthermore the CW25 can
also acquire the satellites in these locations when using Network Assistance techniques, or pre-loaded information. In
order to obtain this level of performance the CW25 uses an innovative GPS engine built into its BB25 IC, which enables the
system to search in parallel 12,288 time/frequency bins. Not only does this enable better sensitivity but also makes for very
rapid acquisition of the satellites. At outdoor signal levels the time taken to obtain a ‘hot’ position fix is under 2 seconds.
With a size of just over an inch square (25 x 27 mm) the CW25 is specifically designed to be integrated with communi-
cations devices such as GSM, CDMA, UMTS modems or any other communications medium.The CW25 is also optimised
for the output of time/ frequency information.
Key Features of the CW25 include:
• Enables indoor use
–155 dBm acquisition with network assist
–156 dBm tracking
–473 dBW acquisition stand alone
• Rapid Time To Fix
<2 second outdoor
<5 second indoor (-148dBm)
• Standalone CW25 module
No GPS knowledge required for hardware integration
• Module dimensions 25 mm x 27 mm x 4.2 mm
This document provides information on the Hardware and Software elements of the CW25.
Key information includes:
• Specification
• Physical Characteristics
CW25 Dimensions, castellation information
Solder Pad and placement information
• Signal Descriptions
• Features
• Application Information
The CW25 is available in a number of standard software builds, depending on the application for which it is to be used. In
special cases, the CW25 may be supplied with a slightly different hardware build. The specifications in this manual refer to
the standard builds.

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CW25 Software User Manual Page 5 of 50 Rev 03 Date: 06/16/08
1. DESCRIPTION continued
1.2 GLOBAL POSITIONING SYSTEM (GPS)
The Global Positioning System (GPS) is a military satellite based navigation system developed by the U.S. Department of
Defence, which is also made freely available to civil users.
Civilian use of GPS is made available at the user’s own risk, subject to the prevailing DoD policy or limitations, and to
individuals understanding of how to use the GPS.
In today’s satellite constellation there are a minimum of 24 operational satellites (plus several operational spares) in 6
orbital planes, at an altitude of about 22,000 km. The GPS system can give accurate 3-D position, velocity, time, and fre-
quency, 24 hours a day, anywhere around the world.
GPS satellites transmit a code for timing purposes, and also a ‘Navigation message’, which includes their exact orbital
location and system integrity data. Receivers use this information, together with data from their internal almanacs, to pre-
cisely establish the satellite location.The receiver determines position by measuring the time taken for these signals to
arrive. At least three satellites are required to determine latitude and longitude if your altitude is known (e.g. a ship at sea),
and at least a fourth to obtain a 3-D fix.
1.3 GPS positioning and navigation
The CW25 Receiver needs to be able to see at least 4 satellite vehicles (SV’s) to obtain an accurate 3-D position fix. When
travelling in a valley or built-up area, or under heavy tree cover, you will experience difficulty acquiring and maintaining a
coherent satellite lock. Complete satellite lock may be lost, or only enough satellites (3) tracked to be able to compute a 2-
D position fix or even a poor 3D fix due to insufficient satellite geometry (i.e. poor DOP). Note also, that inside a building or
beneath a bridge, it probably will not be possible to update a position fix.The Receiver can operate in 2-D mode if it goes
down to seeing only 3 satellites by assuming its height remains constant. But this assumption can lead to very large errors,
especially when a change in height does occur. A 2-D position fix is not to be considered a good or accurate fix; it is simply
“better than nothing”.
The receiver’s antenna must have a clear view of the sky to acquire satellite lock. Remember always, it is the location
of the antenna that will be given as the position fix. If the antenna is mounted on a vehicle, survey pole, or backpack, al-
lowance for this must be made when using the solution.
To measure the range from the satellite to the receiver, two criteria are required: signal transmission time, and signal
reception time. All GPS satellites have several atomic clocks that keep precise time and these are used to time-tag the
message (i.e. code the transmission time onto the signal) and to control the transmission sequence of the coded signal.
The receiver has an internal clock to precisely identify the arrival time of the signal. Transit speed of the signal is a known
constant (the speed of light), therefore: time x speed of light = distance.
Once the receiver calculates the range to a satellite, it knows that it lies somewhere on an imaginary sphere whose
radius is equal to this range. If a second satellite is then found, a second sphere can again be calculated from this range
information. The receiver will now know that it lies somewhere on the circle of points produced where these two spheres
intersect.
When a third satellite is detected and a range determined, a third sphere would intersect the area formed by the other
two.This intersection occurs at just two points.The correct point is apparent to the user, who will at least have a very rough
idea of position. A fourth satellite is then used to synchronise the receiver clock to the satellite clocks.
In practice, just 4 satellite measurements are sufficient for the receiver to determine a position, as one of the two points will
be totally unreasonable (possibly many kilometres out into space).
This assumes the satellite and receiver timing to be identical. In reality, when the CW25 Receiver compares the incom-
ing signal with its own internal copy of the code and clock, the two will no longer be synchronised. Timing error in the satel-
lite clocks, the Receiver, and other anomalies, mean that the measurement of the signals transit time is in error. This
effectively, is a constant for all satellites, since each measurement is made simultaneously on parallel tracking channels.
Because of this, the resultant ranges calculated are known as “pseudo-ranges”.
To overcome these errors, the CW25 Receiver then matches or “skews” its own code to become synchronous with the
satellite signal.This is repeated for all satellites in turn, thus measuring the relative transit times of individual signals. By
accurately knowing all satellite positions, and measuring the signal transit times, the user’s position can be accurately
determined.
Utilizing its considerable processing power, the CW25 Receiver rapidly updates these calculations from satellite data to
provide a real time position fix. Memory options allow storage of navigation and position data for subsequent post-pro-
cessing or post-mission analysis, all within a single unit.

CW25 Software User Manual Page 6 of 50 Rev 03 Date: 06/16/08
Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
1.4 Standard positioning service (SPS)
Civil users worldwide are able to use the SPS without restriction or charge.
Dilution Of Precision (DOP) is a measure of the satellite geometry, and is an indicator of the potential quality of the solu-
tions.The lower the numerical value, the better the potential accuracy (for example, a PDOP below 3 indicates good satel-
lite geometry). For 3-D positioning, fluctuations in DOP can be harmful to the solution, especially in Kinematic/Dynamic
modes.
The following DOP terms are computed by CW25:
HDOP Horizontal Dilution of Precision (Latitude, Longitude)
VDOP Vertical Dilution of Precision (Height)
TDOP Time Dilution of Precision (Timing errors)
PDOP Position Dilution of Precision (3-D positioning)
GDOP Geometric Dilution of Precision (3-D position & Time)
Estimated accuracy = DOP x measurement accuracy
While each of these terms can be individually computed, they are formed from co-variances, and are not independent
of each other. For example, a high TDOP will cause receiver clock errors that will eventually result in increased position
errors.
Horizontal accuracy figure of 95% is the equivalent to 2RMS (twice root-mean-square), or twice the standard deviation
radial error.
Similarly, for vertical and time errors, a figure of 95% is the value of 2 standard deviations of vertical or time error.
• Root-mean-square (RMS) error is the value of one standard deviation (67%) of error.
• Circular Error Probability (CEP) is the value of the radius of a circle, centred at a position containing 50% of the
position estimates.
• Spherical Error Probability (SEP) is the spherical equivalent of CEP, which is centred at a position containing
50% of the position estimates.
CEP and SEP are not affected by large errors, which could make the values an overly optimistic measurement. These
probability statistics are not suitable for use in a high accuracy positioning system. The CW25 reports all accuracy’s in the
form of a standard deviation (RMS) value.
1.5 Precise positioning service (PPS)
This service is only available to authorised users with cryptographic equipment and special receivers. Access is limited to
the U.S. and allied military, U.S. Government agencies, and selected civil users specifically approved by the U.S. Govern-
ment.
1. DESCRIPTION continued

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CW25 Software User Manual Page 7 of 50 Rev 03 Date: 06/16/08
2. SPECIFICATION
2.1 Performance
CW25 GPS RECEIVER SPECIFICATIONS1
Physical Module dimensions 25mm (D) x 27mm (W) x 4.2mm (H)
Supply voltages 3V3 (Digital I/O), 3V3 (RF), 1V8 (Core option), 3V (Standby Battery)
Operating Temp -30°C to +80°C 2
Storage Temp -40°C to +85°C 2
Humidity 5% to 95% non-condensing
Max Velocity / Altitude 515ms-1 / 18,000m
(increased rating version available subject to export license)
Max Acceleration / Jerk 4g / 1gs-1 (sustained for less than 5 seconds)
Sensitivity Acquisition with network assist -155dBm
Tracking -156dBm
Acquisition Stand Alone -143dBm
Acquisition Hot Start with network assist Outdoor: <2s
Time Indoor (-148dBm): <5s
Stand Alone (Outdoor) Cold: <45s
Warm: <38s
Hot: <5s
Re-acquisition: <1s (90% confidence)
Accuracy Position: Outdoor / Indoor <5m rms / <50m rms
Velocity <0.05ms-1
Latency <200ms
Raw Measurement Accuracy Pseudorange <0.3m rms, Carrier phase <5mm rms
Tracking Code and carrier coherent
Power 1 fix per second 0.6W typically
Coma Mode Current <10mA
(RF3V3+DIG3V3)
Standby Current (VBATT) 1.5µA
Interfaces Serial 3 UART ports, CMOS levels
Multi function I/O 1PPS
Frequency Output available on GPIO [0]
Event Counter/Timer Input
Up to 4 x GPIO (multi-function)
2 x LED Status Drive
I2C, External Clock (on special build)
Protocols Network Assist, NMEA 0183, Proprietary ASCII and binary message formats
1pps Timing Output 30ns rms accuracy, <5ns resolution, Factory customisable pulse width
Event Input 30ns rms accuracy, <10ns resolution
Frequency Output (GPIO [0]) 0 MHz to 20 MHz (CW25-NAV)
10 Hz to 30 MHz (CW25-TIM)
Receiver Type 12 parallel channel x 32 taps up to 32 point FFT. Channels, taps
and FFT can be switched off to minimize power or simulate
simpler designs.
General Processor ARM 966E-S on a 0.18 micron process at up to 120 MHz.
Note: 1. The features listed above may require specific software builds and may not all be available in the initial release.
2. Please contact factory for other temperature options.
Table 1 CW25 Specification
2.2 Recommended Ratings
Symbol Parameter Min Max Units
RF_3V3 RF Supply Voltage +3.0 +3.6 Volts
DIG_3V3 Digital Supply Voltage +3.0 +3.6 Volts
DIG_1V8 Digital Supply Voltage +1.65 +1.95 Volts
VBATT Battery Backup Voltage +2.7 +3.5 Volts
ANT_SUPPLY Antenna Supply Voltage +3.0 +12 Volts
Table 2 Absolute Maximum Ratings

CW25 Software User Manual Page 8 of 50 Rev 03 Date: 06/16/08
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Figure 1 Block Diagram
RF Block
Front
End
Filter
Clock
IF
Filter
Regulator
& Reset Regulator
ANT_SUPPLY RF_3V3 DIG_3V3
RF_IN
TRIM/EXT_CLK
DIG_1V8/+1V8_OUT
RTC &
EEPROM
NPOR VBATT
I2C
Control
Emulation
Comms & I/O
RF25IC BB25IC
2.4 Block Diagram
2.3 Absolute Maximum Ratings
Symbol Parameter Min Max Units
RF_3V3 RF Supply Voltage -0.3 +6.5 Volts
DIG_1V8 Digital Supply Voltage -0.3 +2.0 Volts
DIG_3V3 Digital Supply Voltage -0.3 +3.7 Volts
VBATT Battery Backup Voltage -0.5 +7.0 Volts
ANT_SUPPLY Antenna Supply Voltage -15 +15 Volts
DIG_SIG_IN Any Digital Input Signal -0.3 +5.5 Volts
RF_IN RF Input -15 +15 Volts
TSTORE Storage temperature -40 +85 °C
IOUT Digital Signal Output Current -6 +6 mA
Table 3 Absolute Maximum Ratings
2. SPECIFICATION continued

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CW25 Software User Manual Page 9 of 50 Rev 03 Date: 06/16/08
3. PHYSICAL CHARACTERISTICS
The CW25 is a multi-chip module (MCM) built on an FR4 fiberglass PCB. All digital and power connections to the MCM
are via castellations on the 25 x 27 mm PCB. The RF connection is via castellations or an RF connector. The general ar-
rangement of the CW25 is shown in the diagram below. Dimensions are in mm (inches/1000).
O
.
: . - -
HIROSE H.FL CONNECTOR
PART NO:H.FL-R-SMT
Figure 2 CW25 Form and Size
3.1 Physical Interface Details
The interface to the CW25 is via 1mm castellation on a 2mm pitch. There are 42 connections in all. There is also an RF
connector for connecting to the GPS antenna. The details of the interface connections are given below.
Pin Function Pin Function
1 TX[0] 22 TMS
2 RX [0] 23 RF_GND
3 TX[2] 24 RF_IN
4 RX [2]/EV2_IN 25 RF_GND
5 TX[1] 26 ANT_SUPPLY
6 RX [1] 27 VBATT
7 EXT_CLK 28 N2WCK
8 LED_RED 29 N2WDA
9 LED_GRN 30 USBP
10 NRESET 31 USBN
11 BOOTSEL 32 FREQ_OUT 3
12 TRIM 33 +1V8_OUT
13 TDO 34 DIG_1V8
14 TDI 35 DIG_GND
15 NTRST 36 DIG_3V3
16 NPOR 37 EVENT_IN
17 RFV_OUT 38 1PPS
18 RF_GND 39 GPIO [0]/PWM_OUT
19 RF_3V3 40 GPIO [1]/TIME_SYNC
20 TCK 41 GPIO [2]/NEXT_INT
21 JTAGSEL/RTCK 42 GPIO [3]/FREQ_IN
Note: 3. Frequency Output is available on pin 32 (FREQ_OUT) with custom software only.
Table 4 CW25 Signal List

CW25 Software User Manual Page 10 of 50 Rev 03 Date: 06/16/08
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RF_IN
PIN 22
Figure 3 MCM Dimensions
Figure 4 Solder Pad Size and Placement
3.3 Solder Pad Size and Placement
It is recommended that the footprint of the solder pad under each castellation be 2mm x 1mm, centered on the nominal
center point of the radius of the castellation.The castellations are gold plated and so are lead free. Note that if the RF_IN
connector is being used, there should not be a pad or solder resist under the RF_IN castellation. If the RF_IN castellation
is to be used, the pad should be shortened by 0.5mm underneath the CW25 and standard RF design practices must be
observed.The diagram below shows the placement of the pads under the castellations.
3.2 MCM Dimensions
The figure below provides the dimensions of the positioning of the CW25 castellations. Dimensions are in mm (inches/1000).
3. PHYSICAL CHARACTERISTICS continued

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CW25 Software User Manual Page 11 of 50 Rev 03 Date: 06/16/08
4. SIGNAL DESCRIPTION
The signals on the CW25 are described in the table below. All Test, Control and I/O ports are CMOS 3.3V compatible un-
less specified otherwise.
4.1 Power Signals
RF_3V3 Type: Power Direction: Input Pin: 19
The RF supply input.This 3.3V ± 10% input supplies the 3.0V LDO regulator in the RF
section of the CW25. It is important that this supply is well filtered with no more that 50mV
peak to peak noise with respect to RF_GND.
RF_GND Type: Power Direction: Input/Output Pins: 18, 23, 25
The RF input ground connect to common ground. This is the return path for the RF_3V3
supply and the ground for the antenna feed.The RF_GND must be tied to the DIG_GND
externally to the CW25.
RFV_OUT Type: Power Direction: Output Pin: 17
The output from the LDO regulator (3.0V) that is powered by the RF_3V3 signal. This
supplies the power to the RF subsystem of the CW25. This may also be used to power
external RF components but care must be taken not to inject noise onto this signal. No more
than an additional 30mA may be taken from this signal by external circuitry.
ANT_SUPPLY Type: Power Direction: Input Pin: 26
The antenna supply voltage. This may be used to supply power to the RF_IN signal, for use
by an active antenna. The maximum voltage should not exceed ±15V and the current should
be limited to 50mA to prevent damage to the CW25.
DIG_3V3 Type: Power Direction: Input Pin: 36
The digital supply input.This 3.3V ± 10% input supplies the I/O ring of the BB25IC chip and
the LDO regulator in the digital section of the CW25. It is important that this supply is well
filtered with no more that 50mV peak to peak noise with respect to DIG_GND.
DIG_1V8 Type: Power Direction: Input Pin: 34
The 1.8V ± 5% digital core supply for the BB25IC. This is normally connected directly to the
+1V8_OUT signal. However, if an external 1.8V ± 5% is available, a lower overall system
power consumption may be achieved by using an external supply.
+1V8_OUT Type: Power Direction: Output Pin: 33
The 1.8V output from the LDO regulator that is powered by the DIG_3V3 signal. Normally,
this is connected to the DIG_1V8 signal.This loops back the regulated 1.8V to run the
processor core. If not connected the core will not run. This may also be used to power
external logic but care must be taken not to inject noise onto this signal. No more than an
additional 50mA may be taken from this signal by external logic.
DIG_GND Type: Power Direction: Input/Output Pin: 35
The digital ground. This is the return path for the DIG_3V3 supply and the ground reference
for all the digital I/O.The DIG_GND must be tied to the RF_GND externally to the CW25.
VBATT Type: Power Direction: Input/Output Pin: 27
The battery backup supply. The CW25 has an on board Real Time Clock (RTC).This is
powered from the VBATT signal. A supply of typically 3V (greater than 2.5V and less than
DIG_3V3) should be applied to this signal. This signal can be left floating if not required. The
input has a blocking diode and so rechargeable batteries will need an external charging
circuit. Typically, a 1K resister in series with this signal and the external battery will provide
an easy method of measuring the current consumption from VBATT during test.

CW25 Software User Manual Page 12 of 50 Rev 03 Date: 06/16/08
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4.2 RF Signals
RF_IN Type: RF Direction: Input Pin: 24
The RF input signal.This attaches to the GPS antenna. Standard RF design rules must be
used when tracking to this signal. This signal has an RF blocked connection to the
ANT_SUPPLY signal.This is the same signal presented on the RF connector on the CW25.
Only one antenna connection should be made. If the RF connector is to be used, then there
should be no connection, even an unconnected pad, to this castellation.
TRIM Type: RF Direction: Input Pin: 12
This signal trims the output frequency of the VCTCXO.This signal is normally left open.
When floating, this signal is biased to the control voltage of the VCTCXO. Any noise injected
into this signal will severely compromise the performance of the CW25. This signal should
only be used in conjunction with specific application notes.
EXT_CLK Type: RF Direction: Input Pin: 7
This input is the external clock input. This signal is to be used only in special builds of the
CS25 that are not fitted with an internal VCTCXO. For the normal build, containing the
VCTCXO, do not connect this input. The external clock is a 20 MHz clipped
sinewave input with an amplitude between 1V and 3V peak to peak.The return path for
this signal is RF_GND.
4.3 Emulation/Test Signals
TDI Type: Test Direction: Input Pin: 14
The Test Data In signal. This is the standard JTAG test data input.
The signal return path is DIG_GND.
TDO Type: Test Direction: Output Pin: 13
The Test Data Out signal. This is the standard JTAG test data output.
The signal return path is DIG_GND.
TCK Type: Test Direction: Input Pin: 20
The Test Clock signal. This is the standard JTAG test clock input.
The signal return path is DIG_GND.
TMS Type: Test Direction: Input Pin: 22
The Test Mode Select signal.This is the standard JTAG test mode input.
The signal return path is DIG_GND.
JTAGSEL/RTCK Type: Test Direction: Input/Output Pin: 21
This is a dual function signal. When the NPOR signal is asserted (low), this signal is an input
and selects the function of the JTAG interface. When high, JTAG emulation into the embedded
ARM9 processor is selected. When low, the BB25IC chip boundary scan mode is selected.
The value on this signal is latched when NPOR de-asserts (goes high). When NPOR is de
asserted (high) and the JTAG emulation mode has been latched, this signal provides the
return clock to the ARM Multi-ICE. Because the ARM9 functions off a single clock domain,
the TCK has to be internally synchronised in the ARM9. This can cause a variable length delay
in the validity of the TDO signal.The RTCK is a synchronised version of the TCK signal.The
Multi-ICE uses the RTCK output signal to indicate when the TDO signal is valid.The signal
return path is DIG_GND. Pull it to VCC (DIG_3V3) through a 1K resistor for normal operation.
NTRST Type: Test Direction: Input Pin: 15
The Test Reset signal. This is the active low JTAG test reset signal.The signal return path is
DIG_GND. Pull it to ground through a 1K resistor for normal operation.
4. SIGNAL DESCRIPTION continued

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CW25 Software User Manual Page 13 of 50 Rev 03 Date: 06/16/08
4.4 Control Signals
NPOR Type: Control Direction: Input/Output Pin: 16
The Power On Reset signal.This active low, open collector signal is the master reset for the
CW25.This should be driven with an open collector reset circuit for a minimum of 100ms. An
external pull-up is not required if the 100K internal pull-up is sufficient. The CW25 can be
held in reset by asserting this signal. The signal can be used to reset external circuitry, but
care must be taken to ensure no DC current is drawn from this signal as the internal pull-up
resistor value is 100K.
NRESET Type: Control Direction: Input/Output Pin: 10
The system reset signal. This active low, open collector signal is generated by the BB25IC
chip in response to the assertion of the NPOR. It may also be driven to reset the ARM9
processor in the BB25IC without completely re-initialising the chip.
BOOTSEL Type: Control Direction: Input Pin: 11
TThe boot select signal.The BB25IC has four boot up modes, but only two are supported by
the CW25.This signal is sampled when the NPOR is de-asserted. If the BOOTSEL signal is
high or left floating, then the CW25 boots from its on-chip FLASH memory. If the BOOTSEL
signal is pulled low, the CW25 boots from its on-chip ROM.
4.5 I/O Signals
TX [0] Type: I/O Direction: Output Pin: 1
The transmit signal for UART 1. This is a standard UART output signal.
The signal return path is DIG_GND.
TX [1] Type: I/O Direction: Output Pin: 5
The transmit signal for UART 2. This is a standard UART output signal.
The signal return path is DIG_GND.
TX [2] Type: I/O Direction: Output Pin: 3
The transmit signal for UART 3. This is a standard UART output signal.
The signal return path is DIG_GND.
RX [0] Type: I/O Direction: Input Pin: 2
The receive signal for UART 1. This is a standard UART input signal.
The signal return path is DIG_GND.
RX [1] Type: I/O Direction: Input Pin: 6
The receive signal for UART 2 . This is a standard UART input signal.
The signal return path is DIG_GND.
RX [2]/EV2_IN Type: I/O Direction: Input Pin: 4
This is a dual mode signal. Normally, this is the receive signal for UART 3, a standard UART
receive signal. Under software control, it can also be used as general purpose I/O or to
detect events. It can be used to detect the timing of the leading edge of the start bit of the
incoming data stream. The signal return path is DIG_GND.
FREQ_OUT Type: I/O Direction: Input/Output Pin: 32
Optional frequency output signal. It is NOT the same signal as Pin 39.This signal is turned off
by default. This is a complex signal which under software can provide any of either an NCO
generated output frequency, a PWM signal, a GPS aligned EPOCH pulse or general purpose
I/O signal.The signal return path is DIG_GND.
1PPS Type: I/O Direction: Input/Output Pin: 38
The 1 pulse per second signal. This is normally a 1 pulse aligned with GPS time, but can
under software control also provide general purpose I/O or an additional even input. The
pulse width of the 1PPS is software selectable with a default of 100µs. The signal return path
is DIG_GND.
4. SIGNAL DESCRIPTION continued

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Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
4.5 I/O Signals continued
EVENT_IN Type: I/O Direction: Input/Output Pin: 37
The event input signal. This is normally an event timer or counter. Events are timed against
GPS time. Under software control, this input can be used as an external 48 MHz input for the
USB interface or this input can also be used for general purpose I/O. The signal return path
is DIG_GND.
N2WCK Type: I/O Direction: Input/Output Pin: 28
The NavSync 2 Wire Clock signal. This is the open collector I2C compatible clock signal for
the 2 wire serial interface. The signal return path is DIG_GND. 4
N2WDA Type: I/O Direction: Input/Output Pin: 29
The NavSync 2 Wire Data signal. This is the open collector I2C compatible data signal for the
2 wire serial interface. The signal return path is DIG_GND. 4
USBP Type: I/O Direction: Input/Output Pin: 30
The positive USB signal. The signal return path is DIG_GND. 5
USBN Type: I/O Direction: Input/Output Pin: 31
The negative USB signal. The signal return path is DIG_GND. 5
LED_RED Type: I/O Direction: Output Pin: 8
This is a dual function signal. Normally this signal is used to drive a red LED. Standard
software builds use this signal to indicate GPS status. In special software builds, this signal
can be used as GPIO. This signal has a 3.3V CMOS drive. A series limiting resistor is
required to limit output current to ±5mA (typically 270 ohms).
The signal return path is DIG_GND.
LED_GRN Type: I/O Direction: Output Pin: 9
This is a dual function signal. Normally this signal is used to drive a green LED. Standard
software builds use this signal to indicate GPS status. In special software builds, this signal
can be used as GPIO.This signal has a 3.3V CMOS drive. A series limiting resistor is
required to limit output current to ±5mA (typically 270 ohms).
The signal return path is DIG_GND.
GPIO[0]/PWM Type: I/O Direction: Input/Output Pin: 39
Normally the GPIO[0]/PWM output provides a Frequency Output that defaults to 10 MHz, and is
user configurable from 10 Hz to 30 MHz signal. The output is enabled on power-up and is
steered by the GPS solution. Custom software versions can also configure this pin for
general I/O, PWM or EPOCH output.The signal return path is DIG_GND.
GPIO[1]/TIME_SYNC Type: I/O Direction: Input/Output Pin: 40
The GPIO[1]/TIME_SYNC pin provides a synchronization pulse generated by the onboard
RTC. Custom software versions can also configure this pin for general pupose I/O, or an
additional PPS output.The signal return path is DIG_GND.
GPIO[2]/NEXT_INT Type: I/O Direction: Input/Output Pin: 41
The GPIO[2]/NEXT_INT output provides an active high status indicator for the Frequency
Output available on pin 39 (GPIO[0]/PWM). Custom software versions can also configure this
pin for general pupose I/O.The signal return path is DIG_GND.
GPIO[3]/FREQ_IN Type: I/O Direction: Input/Output Pin: 42
The GPIO[3]/FREQ_IN output provides an activehigh status 3D fix indicator.This indicator
can also be used to determine the validity of the pin 38 (1PPS) output. The signal return
path is DIG_GND.
Notes
4. Accessible with custom software only.
5. USB is not supported in the current software build. Leave these two pins unconnected.
4. SIGNAL DESCRIPTION continued

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CW25 Software User Manual Page 15 of 50 Rev 03 Date: 06/16/08
5. Features
5.1 Power on Reset
The power on reset for the CW25 is generated on-board by the regulator in the RF section from the RF_3V3 signal. The
RF_3V3 signal must be applied to the CW25 at the same time as the DIG_3V3, if the on-board power on reset is to be
used. If an external source of reset is to be applied to the NPOR signal after both the RF_3V3 and the DIG_3V3 signals are
valid, this restriction does not apply.
5.2 Time Transfer
In order to aid time transfer between fixes during which the CW25 has been unable to maintain an accurate perception of
time (eg. In deep sleep or powered down states), the on-board RTC can be set to provide a signal derived from the
32.768Hz crystal.
5.3 CW25 Embedded Identification
The hardware version number is hard coded onto the CW25; firmware also contains a version number allowing for easy
identification of the hardware and software version in embedded applications.
5.4 Build Options
There are two versions of the CW25 available:
CW25-NAV: This is the general navigation version of the CW25 GPS Receiver. It includes Network Assistance, which al-
lows the receiver to be sent ephemeris data from a base-station (such as the CW55) over a communications link, which
allow the receiver to acquire initial positional lock in harsh environments, down to signal levels of –185dBW (–155dBm).
CW25-TIM: This version of the CW25 has position-hold software included, which allows for very stable output frequency
control for timing applications. CW25-TIM has network assistance and stand - alone operation also. See specification in
Section 2.1
These two options have same physical characteristics and most features have no difference. They are two options with
different software programming included. The table below details the differences.
Options GPIO [0]/PWM_OUT1Dynamics2$PRTHS Commands6
CW25-NAV Defaults to 0 MHz (disabled), Default is 3. VERS, DYNA, ITIM, RSET, INTM,
20 MHz (maximum). Output Maximum is 5. FRQD, UxOP, UxCM
enabled when frequency error
below 10 ppb.
CW25-TIM Defaults to 10 MHz, Default is 1; change to 0 VERS, DYNA, ITTM, RSET, INTM.
30 MHz maximum. after 10-minute location FRQD, UxOP, UxCM
Output always enabled. survey completed.
Receiver must be and
remain stationary.
Table 5 Differences between CW25-NAV and CW25 TIM software
Notes
1. Refer to Section 8.3.10 and Section 13
2. Refer to Section 8.3.6 to see how to set PRTH<Q|S|R>, DYNA Command.

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Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
7. Power Management
The CW25 GPS receiver is a low power module consuming less than 0.6W typically for a 1Hz update of position.The re-
ceiver contains software to dynamically reduce power consumption wherever possible. Where channels and taps are not
needed they are switched off. When the processor is not required it is put into a halt until interrupt state and the chips
clock system is geared down to reduce power consumption. All of these things are performed automatically without any
user configuration. If further power saving is required the receiver can be reprogrammed with smaller GPS configurations
thereby permanently switching off portions of the GPS hardware and allowing the processor speed to be reduced, thereby
saving power.
7.1 Coma Mode
For powered battery application, which needs to reduce the power consumption, it is possible to switch the receiver into
Coma mode.This configures the RF front end into sleep mode, switches off internal peripherals and places the processor
in a sleep state waiting for an interrupt.
Coma mode is initiated through the COMA serial command, details of which can be found in section 8.3.7.
Care must be taken in the implementation of the CW25 to ensure power consumption is minimized. All input pins with-
out bias resistors have potential to float mid rail and consume power during coma mode.Three GPIO pins default as inputs
and do not have bias resistors. GPIO [1]/TIME_SYNC can be factory programmed to provide either an additional PPS out-
put or a time synchronization input to the GPS engine. GPIO [2]/NEXT_INT can provide an interrupt event from an active
low external input. GPIO [3]/FREQ_IN provide a frequency counter input. Care must be taken to ensure that the pins have
external bias resistors off board to ensure they are not left floating. It is recommended that all unterminated test, Control
and I/O ports are pulled high or low as appropriate (making note of the active state of some ports e.g. BSEL), with typically
100k ohms.
6. Operating Modes
6.1 Stand Alone Operation
For stand alone operation the receiver will perform cold starts with no prior knowledge of position or GPS satellite data
such as almanacs and ephemeris provided the antenna has a clear view of the sky to provide signal strengths of 35dB or
higher. The receiver should be allowed to track satellites for a minimum period of 15 minutes to ensure all almanac infor-
mation has been received. The GPS data is stored in the EEPROM memory fitted to the CW25. Once the receiver has
been initialised and has current almanac and ephemeris data it may then be taken indoors for test with low level signals.
Hot starts (current ephemeris data held in EEPROM) can be performed with low level signals (indoors).
6.2 Network Assist Operation
For network assist operation the Navsync Network Assistance Base Station must be connected to an external antenna and
be tracking all satellites in view. The network assistance data connection is provided by an RS232 link between port 3 on
the network assistance base station and port 3 on the CW25.
With the network assistance base station connected the development system can be started in indoor or outdoor envi-
ronments.
For more information on the Network Assistance data format please refer to section 8.4.

Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
CW25 Software User Manual Page 17 of 50 Rev 03 Date: 06/16/08
8. Communication Protocols
Full descriptions of the communications protocols used by the CW25 can be found in section 8.2 and 8.3.
8.1 Port Configuration
There are three serial ports available on the CW25. They are three UARTs of the CW25 receiver.
These are configured as follows:
Port Baud Rate Function
1 38400 NMEA
2 38400 Debug
3 38400 Network Assistance
Table 6 Port Configurations
All ports are configured as 8, bits no Parity, with no handshaking.
8.2 Output Format
There are two types of messages that can be output from the CW25 receiver, these are split into NMEA sentences and
Debug messages. Both types of outputs are ASCII strings.
8.2.1 NMEA Messages
There are two main types of sentence, ‘Approved’ and ‘Proprietary’. All sentences start with $ delimited with commas and
ending with <CR><LF>. Approved sentences are recognized by the first 5 characters after the $, which define both the
kind of talker providing the information (2 characters, GP in the case of a GPS), and the type of information (3 characters).
Proprietary sentences are indicated by a P following the $, as the first of the 5 characters, the next 3 indicating the manu-
facturer (from a listing of mnemonic codes), and the 5th character being selected by that manufacturer for the particular
sentence structure. Proprietary sentences must conform to the general NMEA structures, but are otherwise undefined out-
side of the Manufacturers own documentation.
The following Approved messages are available from the CW25 receiver:
GPGLL - Geographic Position - Latitude longitude
GPGGA - Global Positioning System Fix Data
GPGSA - GNSS DOP and Active Satellites
GPGSV - GNSS Satellites in View
GPRMC - Minimum required sentence
GPVTG - Velocity and track over ground
GPZDA - Date and time
POLYT - Navsync Proprietary time of day message
POLYP - Navsync Proprietary status message
POLYS - Navsync Proprietary satellite status message (GPGGA + GPGSV)
POLYI - Navsync Proprietary net assist information message
Approved NMEA messages
8.2.1.1 GPGLL - Geographic position, Lat/Lon
Latitude and longitude, with time of position fix and status.
$
GPGLL , Latitude, N, Longitude ,E, hhmmss.sss, Status, Mode*cs
Name Description
$GPGLL NMEA sentence header (Position Data)
Latitude User datum latitudedegrees, minutes, decimal minutes format (ddmm.mmmmmm)
N Hemisphere ‘N’= North, or ‘S’ = South
Longitude User datum longitudedegrees, minutes, decimal minutes format (dddmm.mmmmmm)
E Longitude Direction ‘E’= East, or ‘W’ = West
hhmmss.sss UTC Time in hours, minutes, seconds and decimal seconds format.
Status StatusV=navigation receiver warning, A=data valid
Mode Mode indicator:A=Valid, Autonomous, D=Valid, Differential, E=Invalid, Estimated,
N=Invalid, Not valid
Cs Message checksum in hexadecimal

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Copyright ©2007 NavSync Ltd.All Rights Reserved Specifications subject to change without notice.
8.2.1.2 GPGGA - GPS fix data
Time and position, together with GPS fixing related data.
$
GPGGA , hhmmss.sss, Latitude, N, Longitude , E, FS, NoSV, HDOP , Altref , M, msl , M, DiffAge , DiffStation*cs
Name Description
$GPGGA NMEA sentence header (Position Data)
hhmmss.sss UTC Time in hours, minutes, seconds and decimal seconds format.
Latitude User datum latitude degrees, minutes, decimal minutes format (ddmm.mmmmmm)
N Hemisphere ‘N’= North, or ‘S’ = South
Longitude User datum longitudedegrees, minutes, decimal minutes format (dddmm.mmmmmm)
E Longitude Direction:‘E’= East, ‘W’ = West
FS Fix Status: 0 No fix
1 Standard GPS
2 Differential GPS
NoSv Number of satellites used in the position solution
HDOP 2-D Horizontal Dilution of Precision (0.00 to 99.99)
AltRef Altitude (metres) above user datum ellipsoid
M Units of height (metres)
msl Mean Sea Level
M Units of Mean Sea Level (meters)
DiffAge Age of differential correction
DiffStation Differential base station ID
cs Message checksum in hexadecimal
8.2.1.3 GPGSA - GPS DOP and Active satellites
GPS receiver operating mode, satellites used for navigation, and DOP values.
$GPGSA,Smode,FS,sv,sv,sv,sv,,,,,,,,PDOP,HDOP,VDOP*cs
Name Description
$GPGSA NMEA sentence header (Satellite Data)
Smode A= Automatic switching 2D/3D M=Manually fixed 2D/3D
FS Fix Status: 1 No fix
2 2D GPS Fix
3 3D GPS Fix
sv Satellites in use, null for unused fields (12 available fields)
PDOP 3-D Position Dilution of Precision (0.00 to 99.99)
HDOP 2-D Horizontal Dilution of Precision (0.00 to 99.99)
VDOP Vertical Dilution of Precision (0.00 to 99.99)
cs Message checksum in hexadecimal
8. Communication Protocols continued

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CW25 Software User Manual Page 19 of 50 Rev 03 Date: 06/16/08
8.2.1.4 GPGSV - GPS Satellites in View
The number of satellites in view, together with each PRN, elevation and azimuth, and C/No value. Up to four satel-
lite details are transmitted in one message, with up to three messages used as indicated in the first field.
$GPGSV, NoMsg, MsgNo, NoSv{,sv,elv,az,cno}{,sv,elv,az,cno….}*cs
Note: {} designate optional sections that appear only if there is satellite data.
Name Description
$GPGSV NMEA sentence header (Satellite Data)
NoMsg Total number of GPGSV messages being output
MsgNo Number of this messages
NoSv Number of satellites in view
sv Satellites ID
elv Satellite elevation angle (degrees)
az Satellite azimuth angle (degrees)
cno Satellite signal/Noise ration (dB/Hz)
cs Message checksum in hexadecimal
8.2.1.5 GPRMC - Recommended Minimum data
The ‘Recommended Minimum’ sentence is defined by NMEA for GPS/Transit system data.
$GPRMC,hhmmss.sss,status,latitude,N,Hemisphere,longitude,E,spd,cmg,ddmmyy,mv,mvd,Mode*cs
Name Description
$GPRMC NMEA sentence header (Recommended Minimum Sentence)
hhmmss.sss UTC Time in hours, minutes, seconds.
status Status:V=navigation receiver warning, A=data valid
Latitude User datum latitudedegrees, minutes, decimal minutes format (ddmm.mmmmmm)
N Hemisphere:‘N’= North, or ‘S’ = South
Longitude User datum longitude degrees, minutes, decimal minutes format (dddmm.mmmmmm)
E Longitude Direction:‘E’= East, ‘W’ = West
spd Speed over ground (knots).
cmg Course made good
ddmmyy Date in Day, MonthYear format
mv Magnetic variation
mvd Magnetic variation direction
Mode Mode Indicator: D = Valid, Differential, A = Valid, Autonomous, E = Invalid, Estimated,
N = Invalid, Not Valid
cs Message checksum in hexadecimal
8. Communication Protocols continued

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8.2.1.6 GPVTG - Course over ground and Ground speed.
Velocity is given as Course over Ground (COG) and Ground Speed
$GPVTG,cogt,T,cogm ,M ,knots,N,kph,K,Mode*cs
Name Description
$GPVTG NMEA sentence header (Speed and heading)
cogt Course over ground (true)
T True - fixed field
cogm Course over ground (magnetic)
M Magnetic - fixed field
knots Speed over ground (knots)
N Knots - fixed field
kph Speed over ground (kph)
K Kilometers per hour – fixed field
Mode Mode Indicator:D = Valid, Differential, A = Valid, Autonomous, E = Invalid, Estimated,
N = Invalid, Not Valid
cs Message checksum in hexadecimal
8.2.1.7 GPZDA - UTC Time and Date
This message transfers UTC Time and Date. Since the latency of preparing and transferring the message is vari-
able, and the time does not refer to a particular position fix, the seconds’ precision is reduced to 2 decimal places.
$GPZDA,hhmmss.sss,dd,mm,yyyy,Int,Unsigned*cs
Name Description
$GPZDA NMEA sentence header (Time and Date)
hhmmss.sss UTC Time in hours, minutes, seconds.
dd UTC day
mm UTC month
yyyy UTC year
Int Unsigned Local zone hours
Int Unsigned Local zone minutes
kph Speed over ground (kph)
K Kilometers per hour – fixed field
cs Message checksum in hexadecimal
Proprietary NMEA Messages
8.2.1.8 POLYT - Time of Day
$POLYT,hhmmss.sss,ddmmyy, UTC_TOW ,week, GPS_TOW ,Clk_B , Clk_D ,PG,LocalTTag,BAcc,TAcc,BLANK*cs
Name Description
$POLYT Navsync Proprietary NMEA sentence header (Position Data)
hhmmss.sss UTC Time in hours, minutes, seconds and decimal seconds format.
ddmmyy Date in day, month, year format.
UTC_TOW UTC Time of Week (seconds with microseconds resolution)
week GPS week number (continues beyond 1023)
GPS_TOW GPS Time of Week (seconds with microseconds resolution)
Clk_B Receiver clock Bias (nanoseconds)
Clk_D Receiver clock Drift (nanoseconds/second)
PG 1PPS Granularity (nanoseconds)
LocalTTag Local receiver time-tag since start-up [msec]
BAcc Bias Accuracy
TAcc Time Accuracy
cs Message checksum in hexadecimal
8. Communication Protocols continued