VP305 Datasheet, PDF (82/85 Pages) Mitel Networks Corporation – Satellite Channel Decoder

VP305/6
DRAFT - PRELIMINARY DATA
9. APPENDIX 2: LOCK ACQUISITION ALGORITHM.
9.1. Pre conditions.
Set the frequency sweep limits in CR_USWL and CR_LSWL registers, also the reference period
CR_RP, see page 12. Set the carrier threshold CR_THSL = 72 and the carrier sweep rate
CR_SWR = 150.
9.2. Lock acquisition algorithm.
The Symbol loop phase lock acquisition is automatically handled in the VP305/6. It is initiated by
turning on the carrier sweep function with the carrier loop open. The NDAML carrier phase
detector is enabled. These three items are selected in CR_CONFIG[2:0] register 30. Next the
carrier loop is closed and a program loop started to detect when lock occurs.
The carrier phase lock acquisition is indicated in the STATUS register (3) by CR_LC (bit 1) going
high. When this event occurs, the carrier sweep is turned off. The lock condition is checked five
times to ensure it is stable then the program loop is exited.
Example of pseudo code fragment (using decimal number representation):
Write CR_CONFIG = 39 to register address 30. (Sweep on, Loop open, NDAML)
Write CR_CONFIG = 37 to register address 30. (Sweep on, Loop closed, NDAML)
Initialise variables:
TREND = 0, A_FLAG = 0,
Loop: For A_LOOP = 0 to 200 Do
LOOP_STAT = read CR_LC from STATUS[1] register address 3.
If LOOP_STAT = 1 Then
TREND = TREND + 1
Write CR_CONFIG = 36 to register address 30.
(Sweep off, Loop closed, NDAML)
If TREND > 5 Then
A_FLAG = 1
GOTO EX_ACQ
End If
End If
If LOOP_STAT = 0 Then
TREND = 0
End If
Next A_LOOP
EX_ACQ: sucess
If sucessful, the loop exits with A_FLAG = 1, otherwise, A_FLAG = 0.
The duplication or disclosure of data contained on this sheet is subject to the restrictions
on the title page of this document.
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