GP2021
CHx_l_TRACK,
The pattern to load is the register state for the time of the
second code chip. The followinqtable shows the values
required to select one of the 37 GPS 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_SATCNTLand at this DUMP theAccumulated
Data will be valid for the previous code selection. Later
DUMPs will be valid for the new code.
CHx_Q_TRACK,
CHx_l_PROMPT,
CHx_Q_PROMPT
(Read Address)
Bits 15 to 0: Accumulated Data registers, which are used
on each DUMP to store the 16-bit Integrate-and-Dump
accumulator results. The values contained in the registers
are 2’s complement values with the valid range of the data
from 2215 to 1(21521)
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.
These registers are read-only registers which can be read
at any time. Their content is not protected by any overwrite
protection mechanism, so the set of four registers must be
read soon after an ACCUM_INT to be sure that newer
data will not cause an overwrite part way through the set.
The CHx_l_PROMPT and CHx_Q_PROMPT contain the
Accumulated Data from the Prompt arm. The
CHx_l_TRACK and CHx_Q_TRACK contain the
Accumulated Data from the Tracking arm.
Notes:
G PRN sequences 33 to 37 are reserved for non-satellite
uses (e.g. Ground transmitters - ‘Pseudo-Lites’)
G C/A codes 34 and 37 are equivalent.
G PRN sequences 120 to 138 are selected for the Wide
Area Augmentation System (WAAS).
G PRN sequences 201 to 211 are selected for INMARSAT
GIC (GPS Integrity Channel) use.
To track satellites correctly, only data read with the
CHx_NEW_ACCUM_DATA bit set High should be used.
An overflow or underflow condition cannot be reached.
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 Siew.
Subsequent cycles of the PRN sequence will be correct
for the chosen satellite.
CHx_SATCNTL,
MULTI_ SATCNTL,
ALL_SATCNTL
(Write Address)
GPS
PRN
signal
no.
GPS
PRN
signal
no.
GPS
PRN
signal
no.
G2_LOAD
[9:0]
G2_LOAD
[9:0]
G2_LOAD
[9:0]
Bit name
Bit
(hex)
(hex)
(hex)
15
14-13
12
11
10
GPS_NGLON
TRACK_SEL
PRESET/UPDATEB
CODE_OFF/ONB
SOURCESEL
1
2
3
4
5
6
7
8
3F6
3EC
3D8
3B0
04B
096
2CB
196
32C
3BA
374
1D0
3A0
340
280
100
113
24
25
26
27
28
29
30
31
32
338
270
0E0
1C0
380
22B
056
0AC
158
127
128
129
130
131
132
133
134
135
136
137
138
1E7
2B5
22A
10E
12D
215
337
0C7
0E2
20F
3C0
029
9-0
G2_LOAD (9 to 0)
Table 17
CHx_SATCNTL is a write-only register that can be written
into at any time.Any modification to the content is effective
at the next DUMP in UPDATE mode or at the next TIC in
PRESET mode for all bits, apart from PRESET/UPDATEB,
which defines whether a channel is in PRESETor UPDATE
mode. It is important to program this register first when
starting the initialisation of a PRESET sequence to get the
channe linto PRESET mode, or the other write operations
will act too soon.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
33
34
35
36
37
2B0
058
18B
316
058
201GIC
202GIC
205GIC
206GIC
207GIC
208GIC
209GIC
211GIC
2C4
10A
3E3
0F8
25F
1E7
2B5
10E
120
121
122
123
124
125
126
2C4
30A
1DA
0B2
3E3
0F8
25F
G2_LOAD (9 to 0), bits 9 to 0: C/A CODE SELECTION
FUNCTION: The CHx_SATCNTL register programs the
CODE GENERATOR by setting the G2 register to the
appropriate starting pattern to generate the required GPS
or INMARSAT-GIC codes. The G2_LOAD register may
be programmed at any time but the value is only used
when the code sequence restarts, at the following DUMP
in UPDATE mode, or at the followingTIC in PRESET mode.
226
04C
098
130
260
267
Table 18 G2_LOAD settings required for satellite reception
36
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
