Programming Information
29
input signal is likely to experience a noisy environment, selection of more mod-
erate Eb/No settings will allow for a wider loop bandwidth setting and more
consistent operation.
➢
Eliminating loop stress during demodulator setup
Loop stress can have an affect the demodulator’s tuning process. If the input to
the demodulator is different than the source being applied to the input, it is best
to remove stress from the input loop by switching to an unused input and then
returning to the original input.
If both inputs are being used, prior to tuning the loop, set the demodulator low
pass filter step in register 3Ch to the lowest setting (111b). Set the input low pass
filter (register 31h) value to all zeros. This action filters all inputs during loop
tuning acquisition.
3.4
Critical Register Programming Sequences
The 4430-V/VN has a few critical register programming sequences. These reg-
isters should be programmed in a sequential fashion for proper operation of the
board.
To initialize the board, the critical sequence of registers should be programmed
as shown in the steps below. Registers that are not included below are not con-
sider sequence critical.
1.
Demodulator Carrier Frequency NCO - Synchronous Mode Control
2.
Demodulator Carrier Frequency NCO - Asynchronous Mode Control
3.
Demodulator Carrier Frequency NCO - Register 1 (Bits 7-0)
Demodulator Carrier Frequency NCO - Register 2 (Bits 15-8)
Demodulator Carrier Frequency NCO - Register 3 (Bits 23-16)
Demodulator Carrier Frequency NCO - Register 4 (Bits 31-24)
4.
Demodulator Quadrature NCO - Register 1 (Bits 7-0)
Demodulator Quadrature NCO - Register 2 (Bits 15-8)
Demodulator Quadrature NCO - Register 3 (Bits 23-16)
Demodulator Quadrature NCO - Register 4 (Bits 31-24)
5.
Demodulator Carrier Frequency NCO - Phase Accumulator Reset
Demodulator Quadrature NCO - Phase Accumulator Reset
6.
NCO Strobe/Modulator Control Register (Low Clock Strobe)
7.
NCO Strobe/Modulator Control Register (High Clock Strobe)
8.
Demodulator Carrier Frequency NCO - Phase Accumulator Reset
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