st20-gp1 STMicroelectronics, st20-gp1 Datasheet - Page 17

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

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
Bit
6:0
PRNinitialVal0-1
Bit
9:0
Bit field
NCOphase
Bit field
InitialValue
DSP base address + #C4 to #EC
DSP base address + #100, #104
Function
NCO phase as a signed 7-bit value representing +/-180 degrees total in steps of
2.8125 degrees (360/128).
Function
Initial value of the RTCA-SC159 satellite channel.
Table 3.8 PRNinitialVal0-1 register format
Table 3.7 NCOphase0-11 register format
ST20-GP1
Write only
Write only
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