NavCom LAND-PAK Rev.N - Manual (Page 52)

Technical Reference Manual Rev. N
Blk = All; Blu = IOP w/Internal Radio ; Red = IOP & LBM ; Grn = Engine only 50
0x44 - Packed Almanac loading - 44 bytes
From a cleared memory without an almanac present, it takes 12.5 minutes after satellite lock to
obtain and display complete almanac information. With an almanac present, it takes only a
matter of seconds.
This message contains navigation data corresponding to data-words 3 through 10 (without
parity) of the specified page and subframe. The entire message is repeated 35 times, once for
each of the pages/subframes containing pertinent almanac entries. The Almanac data
subframes for SV PRNs 1 - 32 is sent first, in that order. The final 3 messages consist of those
pages/subframes containing ionosphere and UTC parameters, AS flags, SV configuration and
SV health. ACK/NAK (W1, B2) messaging is used to maintain integrity of the full almanac set.
Record
Usage Command - Yes
Response - Yes
Input: Use 0x20 Wn6 set to 0 to output the entire almanac file; The almanac
can be input to the GPS by sending all 35 almanac records at once;
Output: provides stored almanac
Ref Message Field Description Data Type Units Range Scale
Byte
Count
STX 02 (hex) U08 1
PRA1 99 (hex) U08 1
PRA2 66 (hex) U08 1
ID 44 (hex) U08 1
Length 0x002C U16 2
W1
Command Action
B1=0: Do not store in NVRAM
1: Store in NVRam
B2=0: Do not use ACK/NAK
1: Use ACK/NAK
B6=1: Factory NVRam
0: User NVRam
U08 1
W2
GPS week of collection; since 6
Jan 1980
U16 week 0-65535 2
W3 Time of the week of collection U32 seconds 0-604800 4
W4
Almanac reference week; since 6
Jan 1980
U16 week 0-65535 2
W5 Almanac reference time U32 seconds 0-604800 4
W6 Almanac health U08 1
W7 Almanac source SV U08 1
W8
Data ID
0x01 - 0x19: Page number
B7=0: Subframe 4
1: Subframe 5
U08
1 to 25
1
W9 Data byte 01 U08 1
... Data byte x U08 22
W32 Data byte 24 U08 1
CKSM Checksum U08 1
ETX 03 (hex) U08 1
See notes on next page…