L64724 LSI Logic Corporation, L64724 Datasheet - Page 145

• Manufacturer Part Number: L64724
• Description: Satellite Receiver
• Manufacturer: LSI Logic Corporation

5.7.1 Carrier Acquisition
5.7.1.1 Frequency Sweep Limits
5.7.1.2 Frequency Sweep
Because the outputs of off-the-shelf tuners for DVB satellite receivers
have a large frequency uncertainty (a common order of magnitude is
generator for signal acquisition.
The L64724 implements the entire carrier recovery loop digitally.
During carrier acquisition, the internal frequency sweep generator
searches for the correct frequency. To vary the sweep rate, change the
value in the CAR_SWR register (Group 4, APR 32, 33). To start the
sweep generator, set the CAR_SW bit (Group 4, APR 41) to 1.
The CAR_USWL (Group 4, APR 34, 35) and CAR_LSWL (Group 4,
APR 36, 37) registers set the upper and lower limits, respectively, of the
frequency sweep.
In the case shown in
APR 34, 35) and CAR_LSWL (Group 4, APR 36, 37) registers must be
set. The state of the CAR_SWP_SWAP (Group 4, APR 41) bit controls
the sweep direction. Even though the Carrier Synchronizer controls the
frequency sweep rate based on the value in the CAR_SWR register
(Group 4, APR 32, 33), the microcontroller can monitor the sweep
direction itself.
Figure 5.6
Upper
Sweep
Limit
Carrier Recovery Loop
Lower
Sweep
Limit
Sweep
Start
Point
5 MHz), the L64724 Carrier Synchronizer includes a frequency sweep
frequency
Frequency Sweeping
Figure
time
5.6, both the CAR_USWL (Group 4,
5-13