ST20-GP6 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST20-GP6

GPS PROCESSOR

STMicroelectronics 

ST20-GP6

byte header contains: a ‘sync’ byte with the value #1B, and a ‘sample rate’ byte which contains the

two SampleRate bits from the DSPControl register, see Table 3.1.

Packets are delivered at the rate selected by the DSPControl register, even if new data is not avail-

able. In this case, the data value for the field is set to #8000. This guarantees that synchronism is

maintained between the satellite one-millisecond epochs and the receiver, despite time-of-recep-

tion variations due to the varying path length from the satellite.

16-bit

header

62 byte packet every 840/970/31/62 µs

12 x 16-bit

I values

12 x 16-bit

Q values

Absent 16-bit values padded with #8000

12 x 8-bit

time values

sync

sample

rate

Tracking mode

T[7:6] = 10

T[5:0] = time[5:0]

Acquisition mode

First packet (in SV ms)

T[7:6] = 10

T[5:0] = time[5:0]

Remaining packets

T[7:6] = 00

T[5:0] = sequence number

(sequence numbers are 2 to

16 or 32)

Figure 3.2 DSP packet format

3.1 DSP module registers

The GPS hardware channels of the ST20-GP6 are controlled by three sets of registers:

1 DSPControl register

2 PRNcode0-11 and PRNphase0-11 registers

3 NCOfrequency0-11 and NCOphase0-11 registers

The base addresses for the DSP registers are given in the Memory Map chapter.

DSPControl register

The DSPControl register determines whether the PRN generators are on (normal use) or disabled

(for built-in-self-test of a system), whether the system is in tracking mode (840/970 µs output rate)

or initial acquisition mode (31/62 µs), and selects which of the two rates for each mode. It also

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