st20-gp6 STMicroelectronics, st20-gp6 Datasheet - Page 17

• Manufacturer Part Number: st20-gp6
• Description: Gps Processor
• Manufacturer: STMicroelectronics

erator. Note, the PRNphase0-11 register should only be updated when the PRNphase0-11WrEn
register has been cleared by the hardware.
NCOfrequency0-11 registers
The NCOfrequency0-11 registers hold a signed 18-bit value that is added repetitively, ignoring
overflows, to the accumulated NCO phase from which the NCO sine and cosine waveforms are
generated. The addition is performed at a 264 KHz rate (16.368MHz/62). The accumulated NCO
phase is not accessible to the software, but can be cleared when initialising the channel if enabled
by the DSPControl register.
Each
1.007080078125 Hz.
If the extreme values are written, #1FFFF and #20000, the sine wave generated will be at approxi-
mately +132 KHz, and precisely -132 KHz respectively.
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 mea-
sured on the satellite signal. The register holds a signed 7-bit field representing +/-180 degrees
total in steps of 2.8125 degrees (360/128).
PRNphase0-11WrEn
Bit
0
NCOfrequency0-11
Bit
17:0
NCOphase0-11
Bit
6:0
unit
Bit field
PRNphaseWrEn
Bit field
NCOfrequency
Bit field
NCOphase
value
in
DSP base address + #40 to #6C
DSP base address + #80 to #AC
DSP base address + #C4 to #EC
Table 3.5 PRNphase0-11WrEn register format
Table 3.6 NCOfrequency0-11 register format
the
Function
Set when the corresponding
Function
NCO frequency as a signed 18-bit value.
Function
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
NCOfrequency0-11
PRNphase0-11
register
represents
register is set.
264KHz/(2
Write only
Write only
Read only
ST20-GP6
18
),
17/123
i.e.