L64704 LSI Logic Corporation, L64704 Datasheet - Page 117

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

Figure 5.6
Frequency
Sweeping
CAR_LWSL register (Group 4, APR 31:32), the VCOF block automati-
cally tells the sweep generator to increase the VCO frequency. If the
prescaled frequency is above the upper limit set in the CAR_USWL
register, the VCOF block tells the sweep generator to decrease the VCO
frequency.
frequency within the established limits.
Sweep
Sweep
Sweep
For example, consider the following frequency values:
With these values, the lower prescaled frequency is (480 – 3)/32 =
14.90625 MHz, and the upper prescaled frequency is (480 + 3)/32 =
15.09375 MHz.
Carrier Synchronizer
Upper
Lower
Point
Limit
Limit
Start
VCO nominal frequency = 480 MHz
Frequency uncertainty = 3 MHz
prescaling ratio = 32
f
Figure 5.6
illustrates how the sweep generator keeps the VCO
t
5-13