ST20-GP1 datasheet(17/116 Pages) STMICROELECTRONICS

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ST20-GP1

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NCOphase0-11 registers

The NCOphase0-11 registers contents are added to the accumulated phase to correct the carrier

for the ﬁnal 1 Hz that cannot be resolved by the NCO frequency. This addition is not cumulative,

and the value must be updated regularly by the software as a result of carrier phase errors

measured on the satellite signal. The register holds a signed 7-bit ﬁeld representing +/-180

degrees total in steps of 2.8125 degrees (360/128).

PRNinitialVal0-1 registers

The initial value for the two RTCA-SC159 capable satellites channels should be written to the

PRNinitialVal0-1 registers. The value can be found in the

RTCA-SC159 Specification.

Note: The value written to the register is the Initial Value deﬁned by RTCA-SC159 for the PRN

required. The conversion from ‘big-endian’ as used in the speciﬁcation to ‘little-endian’ as

conventionally used in ST20 architectures has been implemented in the hardware.

If uninitialized by the software, this register defaults to 11 1111 1111 (#3FF) as required for GPS

satellites.

NCOphase0-11

DSP base address + #C4 to #EC

Write only

Bit

Bit ﬁeld

Function

6:0

NCOphase

NCO phase as a signed 7-bit value representing +/-180 degrees total in steps of

2.8125 degrees (360/128).

Table 3.7 NCOphase0-11 register format

PRNinitialVal0-1

DSP base address + #100, #104

Write only

Bit

Bit ﬁeld

Function

9:0

InitialValue

Initial value of the RTCA-SC159 satellite channel.

Table 3.8 PRNinitialVal0-1 register format

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