st20-gp1 STMicroelectronics, st20-gp1 Datasheet - Page 15

• Manufacturer Part Number: st20-gp1
• Description: Gps Processor
• Manufacturer: STMicroelectronics

For channels 0 and 1, RTCA-SC159 satellite codes can also be selected. This is achieved by
setting the PRNcode0-11 register appropriately and also writing the initial value for the satellite to
the PRNinitialVal0-1 register, see Table 3.8. If uninitialized by the software, the PRNinitialVal
register defaults to 11 1111 1111 (#3FF) as required for GPS satellites.
The PRNcode0-11 and PRNinitialVal0-1 registers are normally written only when the satellite is
first chosen.
PRNphase0-11 registers
The PRN0-11phase registers determine the relative delay between the receiver master clock, and
the start of the one millisecond repetitive code sequence. The code sequence starts when the
receiver clock counter (invisible to the software except through message timestamps) reaches the
value written to the PRNphase0-11 register. The PRNphase0-11 register must only be written
once per satellite milliseconds-epoch, which varies from the receiver epoch dynamically due to
satellite motion. Synchronism with the software is achieved by reading the register, when a write
enable flag is returned. If not enabled, the write operation is abandoned by the software.
a. Refer to the US DoD document ICD-GPS-200.
b. It is the responsibility of the software to ensure that when this value is selected, a suitable value has
been written into the PRNinitialVal0-1 register. If this channel is later used for a standard GPS sat-
ellite, the PRNinitialVal0-1 must be set to all ones (#3FF).
Satellite ID
WAAS
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
-
-
-
-
-
b
Table 3.3 PRNcode0-11 register value
PRNcode0-11
register value
#29
#41
#52
#63
#74
#05
#16
#31
#64
#75
#06
#17
#28
#61
#72
#03
#14
#25
#24
#71
#02
#24
#20
Taps selected from G2 shift register
by bits 6 to 4
10
10
10
10
10
10
4
5
6
7
8
9
3
6
7
8
9
6
7
8
9
7
8
by bits 3 to 0
9
1
2
3
4
5
6
1
4
5
6
7
8
1
2
3
4
5
4
1
2
4
0
a
ST20-GP1
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