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Trimble ThunderBolt E GPS Disciplined Clock User Guide 47
Trimble Standard Interface Protocol A
Command Packet 0x38: Request Satellite System Data
This packet requests current satellite data.The GPS receiver returns packet 0x58.
Command Packet 0x39: Set or Request SV Disable and Health Use
Normally the GPS receiver selects only healthy satellites (based on transmitted values
in the ephemeris and almanac) which satisfy all mask values. This packet allows
overriding the internal logic and forces the receiver to either unconditionally disable a
particular satellite or to ignore a bad health flag. The GPS receiver returns packet 0x59
if operation 3 or 6 is requested; otherwise there is no reply.
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".
Note – At power-on and after a reset the default values are set for all satellites.
C
CAUTION – Improperly ignoring health can cause the GPS receiver software to lock up, as
an unhealthy satellite may contain defective data. Use extreme caution in ignoring
satellite health.
Byte Item Type Value Meaning
0 Operation UINT8 1 Must always be '1'
1 Type of data UINT8 2 Almanac
3 Health page, toa, WNa
4 Ionosphere
5UTC
6 Ephemeris
2 Sat PRN UINT8 0 Data not satellite ID specific
1 - 32 Satellite PRN number
Byte Item Type Value Meaning
0 Operation UINT8 1 Enable satellite (default)
2 Disable satellite
3 Request enable/disable status of all 32
satellites
4 Heed health (default)
5 Ignore health
6 Request heed or ignore health on all 32
satellites
1 Sat PRN UINT8 0 All 32 satellites
1-32 Any one satellite PRN number