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32 WAAS GUS Signal Generator User Guide Rev 1
Chapter 5 Messages
SUB-CHIP FIELD
This value specifies the initial sub-chip phase to be loaded into the Code DDS in increments of 1/256 code chip.
Table 20 shows the Sub-Chip field byte and bit format.
Table 20: Sub-Chip Field
CODE CHIP ADVANCE FIELD
This value specifies the initial code chip advance from zero chip count. Table 21 shows the Chip Advance field byte
and bit format.
Table 21: Code Chip Advance Field
SYMBOL ADVANCE FIELD
This value specifies the initial symbol epoch advance from zero epoch count. At 500 SPS, the symbol epoch is 2
ms, at 1000 SPS, the symbol epoch is 1 ms.
Table 22 shows the Symbol Advance field bit format. If 500 SPS is
selected, the MSB indicates which 1 ms epoch is selected within the initial symbol epoch. A ‘0’ indicates that the
even 1 ms epoch is selected within the initial 2 ms symbol epoch. A ‘1’ indicates that the odd 1 ms epoch is selected
within the 2 ms symbol epoch.
Table 22: Symbol Advance Field
L1 I CHANNEL G2 CODER INITIALIZATION FIELD
This field contains the initial state (10 bits) of the L1 I Channel G2 code generator. See Table 23 for the I channel
G2 coder initialization field bit format.
Table 23: L1 I Channel G2 Coder Initialization Field
Byte [8]
D7 D6 D5 D4 D3 D2 D1 D0
MSB LSB
LS Byte [9] MS Byte [10]
D7 D6 D5 D4 D3 D2 D1 D0 D15 D14 D13 D12 D11 D10 D9 D8
LSB MSB
LS Byte [9] MS Byte [10]
D7 D6 D5 D4 D3 D2 D1 D0 D15 D14 D13 D12 D11 D10 D9 D8
LSB MSB
LS Byte [13] MS Byte [14]
D7 D6 D5 D4 D3 D2 D1 D0 - - - - - - D9 D8
LSB MSB
G2I(7) (6) (5) (4) (3) (2) (1) G2I(0) - - - - - - G2I(9) G2I(8)