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7: 12-Channel Correlator
GP4020 GPS Baseband Processor Design Manual 79
the register state for the time of the second code chip. Table 7.28 on page 79 shows the values required to select
one of the 37 GPS, 19 WAAS or the 8 INMARSAT–GIC possible PRN (Pseudo Random Noise) patterns.
In UPDATE mode, the C/A code generated by the CODE GENERATOR will be changed at the DUMP following the
write to CHx_SATCNTL and at this DUMP the Accumulated Data will be valid for the previous code selection. Later
Dumps will be valid for the new code.
If all zeros are loaded into the G2 register, it will not clock out, and the G1 generator code will be seen on the
output. This is an illegal state, which is only of use for chip testing.
Notes:
• PRN sequences 33 to 37 are reserved for non-satellite uses (e.g. Ground transmitters - "Pseudolites")
• C/A codes 34 and 37 are equivalent.
• PRN sequences 120 to 138 are selected for the Wide Area Augmentation System (WAAS).
• PRN sequences 201 to 211 are selected for INMARSAT GIC (GPS Integrity Channel) use.
Due to the initialisation of the Early–Prompt–Late shift register, all codes will always start with a ”1” for the first bit of
the sequence after a Code change or a Code Slew. Subsequent cycles of the PRN sequence will be correct for the
chosen satellite.
GPS PRN
Signal No
G2_LOAD
[9:0]
GPS PRN
Signal No
G2_LOAD
[9:0]
GPS PRN
Signal No
G2_LOAD
[9:0]
1 0x3F6 24 0x338 127 0x1E7
2 0x3EC 25 0x270 128 0x2B5
3 0x3D8 26 0x0E0 129 0x22A
4 0x3B0 27 0x1C0 130 0x10E
5 0x04B 28 0x380 131 0x12D
6 0x096 29 0x22B 132 0x215
7 0x2CB 30 0x056 133 0x337
8 0x196 31 0x0AC 134 0x0C7
9 0x32C 32 0x158 135 0x0E2
10 0x3BA 136 0x20F
11 0x374 33 0x2B0 137 0x3C0
12 0x1D0 34 0x058 138 0x029
13 0x3A0 35 0x18B
14 0x340 36 0x316 201 GIC 0x2C4
15 0x280 37 0x058 202 GIC 0x10A
16 0x100 205 GIC 0x3E3
17 0x113 120 0x2C4 206 GIC 0x0F8
18 0x226 121 0x30A 207 GIC 0x25F
19 0x04C 122 0x1DA 208 GIC 0x1E7
20 0x098 123 0x0B2 209 GIC 0x2B5
21 0x130 124 0x3E3 211 GIC 0x10E
22 0x260 125 0x0F8
23 0x267 126 0x25F
Table 7.28 G2 LOAD settings required for C/A code generator, for valid PRN Numbers