IPR-FIR Altera, IPR-FIR Datasheet - Page 34

• Manufacturer Part Number: IPR-FIR
• Description: IP CORE Renewal Of IP-FIR
• Manufacturer: Altera
• Type: MegaCorer

Specifications of IPR-FIR

• Software Application: IP CORE, DSP Filters And Transforms
• Supported Families: Arria GX, Arria II GX, Cyclone, HardCopy, Stratix
• Core Architecture: FPGA
• Core Sub-architecture: Arria, Cyclone, Stratix
• Rohs Compliant: NA
• Function: Finite Impulse Response Compiler
• License: Renewal License
• Lead Free Status / RoHS Status: na
• Lead Free Status / RoHS Status: na

3–10
FIR Compiler User Guide
1
The FIR Compiler calculates how many bits your filter requires for full resolution
using two methods: actual coefficients or the coefficient bit widths. These parameters
define the maximum positive and negative output values. Select either Bit Width
Only or Actual Coefficients in the Output Specification drop-down box. The FIR
Compiler will extrapolate the number of bits required to represent that range of
values. For full precision, you must use this number of bits in your system.
If your filter has coefficient reloading or multiple sets of coefficients, you must select
Bit Width Only.
You can use full or limited precision for the filtered output (out). To use full precision,
leave the Output Number System set to Full Resolution (default). To limit the
precision, select Custom Resolution or Signed Binary Fractional from the drop down
box.
When the Output Number System is set to Custom Resolution, you can choose to
truncate or saturate the most significant bit (MSB) and to truncate or round the least
significant bit (LSB). Saturation, truncation, and rounding are non-linear operations.
Table 3–2
Table 3–2. Options for Limiting Precision
Figure 3–8
Figure 3–8. Removing Bits from the MSB and LSB
Alternatively, you can select Signed Binary Fractional notation and specify the
number of bits to keep. The FIR Compiler displays how many bits are removed.
MSB
LSB
Bit Range
Bits Removed from MSB
Precision
Full
D15
D14
D13
D12
D11
D10
D9
D8
.
.
D0
shows the options for limiting the precision of your filter.
shows an example of removing bits from the MSB and LSB.
Truncate
Saturate
Truncate
Round
Option
Precision
Limited
D9
D8
.
.
D0
In truncation, the filter disregards specified bits.
In saturation, if the filtered output is greater than the maximum positive
or negative value that can be represented, the output is forced (or
saturated) to the maximum positive or negative value.
Same process as for MSB.
The output is rounded away from zero.
Bits Removed from LSB
Precision
Full
D15
D14
.
.
.
.
D4
D3
D2
D1
D0
Precision
Limited
D11
D10
.
.
.
D1
D0
Result
Bits Removed from both MSB & LSB
Precision
Specify the Input and Output Specifications
Full
D15
D14
D13
D12
.
.
.
D3
D2
D1
D0
© December 2010 Altera Corporation
Chapter 3: Parameter Settings
(Figure
Precision
Limited
D10
D9
.
.
.
D1
D0
3–8).