STA002 datasheet(17/43 Pages) STMICROELECTRONICS

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Carrier frequency registers (CARINTG)

Internal address: 94 H

Reset Value: 00H

MSB

LSB

signed number

This register is formed by the 8 integrator MSBs

of the carrier loop filter.

The value of this register, when the system is

locked, is an image of the frequency offset.

It may be read or written at any time by the micro.

When written the integrator LSBs are reset.

Carrier NCO frequency setting register (IFFREQ)

Internal address: 93 H 92 H 91 H 90 H

Reset Value

: 00H C1H 1DH 37H

MSB

LSB

b31

b30

b29

b28

b27

b26

b25

b24

IFFREQ4

MSB

LSB

b23

b22

b21

b20

b19

b18

b17

b16

IFFREQ3

MSB

LSB

b15

b14

b13

b12

b11

b10

IFFREQ2

MSB

LSB

IFFREQ1

This register is divided into four bytes.

The LSB byte is named IFFREQ1, the MSB is

named IFFREQ4.

The 26 bits value to be written into this register is

given by:

IFFREQ

= INT 



Fck







For example if M_CLK = 39.02687179MHz,

Fck = M_CLK/4

IFFREQ = 12655927 = (C11D37)HEX

which is the Reset Value.

Actual Carrier Frequency Register (CARFREQ)

Internal address: 96 H, 97 H, 98 H

MSB

LSB

b23

b22

b21

b20

b19

b18

b17

b16

CAR FREQ 3

MSB

LSB

b15

b14

b13

b12

b11

b10

CAR FREQ 2

MSB

LSB

CAR FREQ 1

This register contains the actual carrier frequency

value when the system is locked.

It is divided into 3 registers: CARFREQ3, down to

1 (CARFREQ3 is the MSB).

This register may be read at any time and it is

useful to store the value of the recovered carrier.

If the system unlocks (due, to a lack of signal

etc.) the carrier NCO could be initialized with this

value to speed-up the tracking process.

3.4.2 Loop parameters

Like the timing loop the carrier loop is a second

TABLE 1. Timing loop parameters (m= 22; KD = 0.356; M_CLK = 39.02687179MHz)

beta_tmg

012

3456789

fn(Hz)

102

144

204

288

408

577

alpha_tmg

Damping factor

0.71

1.42

2.85

5.70

11.4

22.8

45.6

0.50

1.01

2.01

4.03

8.06

16.1

32.2

0.36

0.71

1.42

2.85

5.70

11.4

22.8

0.25

0.50

1.01

2.01

4.03

8.06

16.1

0.18

0.36

0.71

1.42

2.85

5.70

11.4

0.13

0.25

0.50

1.01

2.01

4.03

8.06

0.09

0.18

0.36

0.71

1.42

2.85

5.70

0.06

0.13

0.25

0.50

1.01

2.01

4.02

0.04

0.09

0.18

0.36

0.71

1.42

2.85

0.03

0.06

0.13

0.25

0.50

1.01

2.01

STA002

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