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A-28 Lassen-SK8 Embedded GPS Module
Trimble Standard Interface Protocol
A.17.20 Command Packet 0x39
Normally the GPS receiver selects only healthy satellites (based on transmitted values in
the ephemeris and almanac) which satisfy all mask values, for use in the position solution.
This packet allows you to override the internal logic and force the receiver to either
unconditionally disable a particular satellite or to ignore a bad health flag. The GPS
receiver returns Packet 0x59 for operation modes 3 and 6 only.
It should be noted that when viewing the satellite disables list, the satellites are not
numbered but are in numerical order. The disabled satellites are signified by a “1” and
enabled satellites are signified by a “0”.
This information is not held in battery-backed memory. At power-on and after a reset the
default values are set for all satellites.
I
Caution – Ignoring satellite health flags can cause the GPS receiver software to lock up.
An unhealthy satellite may contain defective data. Use extreme caution when ignoring
satellite health flags.
A.17.21 Command Packet 0x3C
This packet requests the current satellite tracking status. The GPS receiver returns Packet
0x5C if data is available.
Table A-23. Command Packet 0x39 Data Formats
Byte Item Type Value Meaning
0 Operation Byte 1
2
3
4
5
6
Enable for selection (default)
Disable for selection
Request enable - or - disable
status of all 32 satellites
Heed health on satellite
(default)
Ignore health on satellite
Request heed - or - ignore
health on all 32 satellites
1 Satellite # Byte 0
1 - 32
all 32 satellites
any one satellite PRN number
Table A-24. Command Packet 0x3C Data Format
Byte Item Type Value Meaning
0 Satellite # Byte 0
1 - 32
All satellites in the current
tracking set
Desired satellite