L64780 LSI Logic Corporation, L64780 Datasheet - Page 70

• Manufacturer Part Number: L64780
• Description: Dvb-t Cofdm Demodulator Technical Manual 2/00
• Manufacturer: LSI Logic Corporation

4-18
AFC_POL
AFC_SENSITIVITY
Register Descriptions
If the Loop is stalled (1), the integrator inside the L64780
keeps its internal value constant, enabling you to set the
Frequency Offset by means of software (using
AFC_INIT_FREQ).
The initial condition for the AFC_STALL is 0, the normal
working mode.
AFC VCO Polarity
These bits determine the polarity of the external VCO.
If the polarity is positive (this bit is 0), the output
frequency of the external down-converter must increase
with increasing voltage from the AFCOUT pin.
If the polarity is negative (this bit is 1), the output
frequency of the external down-converter must decrease
with increasing voltage from the AFCOUT pin.
The initial condition for the AFC_POL is 0 (positive).
AFC Loop Gain
These bits adjust the AFC Gain of the Loop Filter. The
value is set according to the sensitivity of the AFC input
of the external down-converter. The values in digital AFC
loop mode are:
The initial condition for these bits is 0b110, or
AFC_SENSITIVITY[2:0]
K
0
0
0
0
1
1
1
1
SENS
9.8
0
0
1
1
0
0
1
1
10
–
4
.
0
1
0
1
0
1
0
1
Definition
K
K
K
K
K
K
K
K
SENS
SENS
SENS
SENS
SENS
SENS
SENS
SENS
1.52
3
6
1.22
2.44
4.88
9.8
1.95
10
10
10
–
–
10
10
10
10
10
5
5
–
4
–
–
–
–
–
5
4
4
4
3
R/W [2:0]
R/W 3