STS1TX datasheet(37/70 Pages) STMICROELECTRONICS

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STS1TX

Transmission and reception

9.2

RF channel frequency settings

RF channels can be defined using the CHSPACE and CHNUM registers.

The channel center frequency can be programmed as:

Equation 2

This allows the setting of up to 256 channels with a programmable raster. The raster

granularity is about 793 Hz at 26 MHz and becomes about 1587 Hz at 52 MHz.

The actual channel spacing is from 793 Hz to 202342 Hz in 793 Hz steps for the 26 MHz

configuration and from 1587 to 404685 Hz in 1587 Hz steps for the 52 MHz configuration.

The base carrier frequency, i.e. the carrier frequency of channel #0, is controlled by the

SYNT0, SYNT1, SYNT2, and SYNT3 registers according to the following formula:

Equation 3

where:

•

fXO is the frequency of the XTAL oscillator (typically 24 MHz, 26 MHz, 48 MHz, or 52

MHz)

•

SYNT is a programmable 26-bit integer.

Equation 4

Equation 5

The offset frequency is a correction term which can be set to compensate the crystal

inaccuracy after e.g. lab calibration.

Equation 6

CHNUM

CHSPACE

offset

base

⋅













⋅

base

SYNT

M, S

B5)

(

)

(

)

(

)

very

{{

1 if REFDIV 0 (internal reference divider is disabled)

2 if REFDIV 1 (internal reference divider is enabled)







OFFSET

offset

⋅

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