Garmin GPS 16 HVS Receiver 010-00258-53 Manuale Utente
Codici prodotto
010-00258-53
190-00228-21
GPS 16/17 Technical Specifications
Rev. A
Page 27
Ephemeris Download Procedure
The following is the sequence of events that occurs when downloading ephemeris.
Send a packet containing the command that requests ephemeris data (
IOP_DOWN_LOAD_EPH)
. The packet should
look like this:
TX Packet: Ephemeris Data Request
Byte Description
Name
HEX Value
Delimiter
DLE
0x10
Command Data ID
IOP_CMND_DATA
0x0A
Number of bytes in data
SIZE
0x02
Request to D/L ephemeris
IOP_DOWN_LOAD_EPH
0x5D
Pad to 2 bytes
DATA
0x00
Checksum calculation
CHKSUM
0x97
*
Delimiter
DLE
0x10
End
ETX
0x03
*
From now on, checksum calculation will not be shown for every packet example
The unit will return an acknowledgement packet that will look like this:
RX Packet: Acknowledgement
Byte Description
Name
HEX Value
Delimiter
DLE
0x10
Acknowledgement ID
IOP_ACK_BYTE
0x06
Number of bytes in data
SIZE
0x02
Request to D/L ephemeris
IOP_CMND_DATA
0x0A
Pad
DATA
0x00
Checksum calculation
CHKSUM
----
Delimiter
DLE
0x10
End of packet
ETX
0x03
Then, the unit will immediately send a packet communicating how many data packets to expect for the ephemeris
download (a maximum of twelve):
download (a maximum of twelve):
RX Packet: Number of Data Packets to Expect
Byte Description
Name
HEX Value
Delimiter
DLE
0x10
Record ID
IOP_RECORDS
0x1B
Number of bytes in data
SIZE
0x02
Number of records
NUM_SV
0x0C
Pad
DATA
0x00
Checksum calculation
CHKSUM
----
Delimiter
DLE
0x10
End of packet
ETX
0x03
This packet requires acknowledgement, as shown below (note that the data field contains the
IOP_RECORDS
ID to
indicate the acknowledgement of the
IOP_RECORDS
packet):
TX Packet: Acknowledgement
Byte Description
Name
HEX Value
Delimiter
DLE
0x10
Record ID
IOP_ACK_BYTE
0x06
Number of bytes in data
SIZE
0x02
Pad
DATA
0x00
ID of packet being ACK’d
IOP_RECORDS
0x1B
Checksum calculation
CHKSUM
----
Delimiter
DLE
0x10
End of packet
ETX
0x03