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SPPDF-01 Development Suite
User’s Manual
SPPDB-01
Manual FIR Filter Selection
Appendix A - Example 1
For Manual FIR Filter Selection a 10-bit DIP-switch on the SPPDB-01 is used to select a
filter to run for each SPPDM-01 channel. It is designated as D
0
to D
9
, where D
9
is the most sig-
nificant bit (MSB), while D
0
is the least significant bit (LSB). In the SPPDF-01 Suite, D
9
is used
as a channel selection bit (Channel 1 (0) and Channel 2 (1)). D
0
to D
8
are used as frequency
selection bits. The DSP checks the switch status at the rate of 48 kHz. If the status has
changed, the DSP follows these steps:
•
Check D
9
bit. If D
9
is ‘0’, the filter number selection is set for channel one (1), if D
9
is
‘1’, the filter number selection is set for channel two (2).
•
Extract bits D
0
to D
8
and get the filter setting number.
•
According to the filter number, calculate the coefficient set address in flash memory.
•
Copy the coefficient set into the DSP internal memory.
•
Run with new coefficients.
With 9-bit tuning (D
0
thru D
8
), up to 512 different filter numbers (coefficients) can be
selected for each channel on SPPDM-01. Although the FCG can create 1 to 682 sets of filter
coefficients at one time, only the first 512 sets are accessible. To select a filter number, set D
0
to
D
8
according to the following formula.
FN=1+D
0
+D
1
*2+D
2
*4+D
3
*8+D
4
*16+D
5
*32+D
6
*64+D
7
*128+D
8
*256. Where FN means Filter
Number.
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