AFE8201PFBR BURR-BROWN [Burr-Brown Corporation], AFE8201PFBR Datasheet - Page 15

• Manufacturer Part Number: AFE8201PFBR
• Description: IF Analog-to-Digital Converter with Digital Downconverter
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

For example, using the ODD mode in the first cycle of MCLK, the filter coefficient at BASE_ADDR is applied to two
values in data memory, the most recent at address N and the oldest at address N+10. In the next cycle of MCLK the
coefficient at BASE_ADDR+1 is applied to the data values at N+1 and N+9, and so on until the last coefficient at
BASE_ADDR+5 is reached. Because this is an odd filter, the final coefficient is applied only to the data value at
address N+5. The full cycle is shown in Table 3.
Figure 17 clearly illustrates that the overall filter length is different in different filter mode even if NCOEFF is
unchanged. For NCOEFF = 6, filter length ranges from 6 taps for ARBITRARY mode to 19 taps for HALFBAND mode.
The dc gain of the FIR filter depends on the coefficient values and the filter mode.
For ODD mode and for HALFBAND mode, the dc gain is given by:
where h
For EVEN mode the dc gain is:
while for ARBITRARY mode the gain is:
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n
is the nth of NCOEFF filter coefficients stored in memory.
Cycle
1
2
3
4
5
6
Table 3. ODD Mode Calculation Example with Six Filter Coefficients
GAIN + h
GAIN +
GAIN +
NCOEFF
Filter Coefficient Address
NCOEFF
)
n + 1
NCOEFF
n + 1
S
S
BASE_ADDR+1
BASE_ADDR+2
BASE_ADDR+3
BASE_ADDR+4
BASE_ADDR+5
NCOEFF * 1
BASE_ADDR
n + 1
2h
S
h
n
n
2
2h
2
15
15
n
* 1
* 1
2
15
* 1
SBWS016A − OCTOBER 2003 − REVISED JANUARY 2005
Applied to Data Address
N+1 and N+9
N+2 and N+8
N+3 and N+7
N+4 and N+6
N and N+10
N+5
AFE8201
(10)
(12)
(11)
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