L64704 LSI Logic Corporation, L64704 Datasheet - Page 196

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

B.3
QPSK
Demodulator
Configuration
Example
B-8
Step 5. Set the CAR_SW and CAR_OPEN bits in the Carrier Loop
Step 6. If the carrier still does not lock, check the following parameters:
Step 7. If the carrier seems to lock and stops sweeping, then check the
Step 8. If all of the flags in the Carrier and FEC Synchronization Status
This section shows an example of how to configure the QPSK Demodu-
lator section of the L64704 through its microcontroller interface. This
example configuration is optimized for fixed rate operation with the fol-
lowing parameters:
L64704 Application Notes
Transmission Rate:
Clock VCO:
Carrier VCO:
Xtal OSC:
ADC:
DC offset control:
Loop Configuration register. These bits control the sweep direc-
tion and the polarity of the CAR_VCOxN/P outputs.
Configuration register to b01. The loop should now lock or at
least slow down near the center of the frequency range.
Each one of these parameters affects the behavior of the loop.
Carrier and FEC Synchronization Status register (Group 3,
APR 9) for the status. All flags should be set to one when the
carrier and clock are locked.
register are set to 1, then set the CAR_SW and CAR_OPEN
bits in the Carrier Loop Configuration register r to b00, This
turns off the sweep.
CAR_KP
CAR_KD
CAR_SWR
Recalculate RC values
42.6 Mbps (21.3 Mbaud)
42.6 MHz (1 MHz/V)
479.75 MHz (1.8 MHz/V)
10.00 MHz
Input: 1.0 V p-to-p
not used