
Altera Corporation
7–13
September 2004
Stratix Device Handbook, Volume 2
Implementing High Performance DSP Functions in Stratix & Stratix GX Devices
Basic FIR Filter Implementation Results
Table 7–6 shows the results of the serial implementation of an 18-bit 8 tap
Basic FIR Filter Design Example
Download the Basic FIR Filter (base_fir.zip) design example from the
Time-Domain Multiplexed FIR Filters
A TDM FIR filter is clocked n-times faster than the sample rate in order to
reuse the same hardware. Consider the 8-tap filter shown in
Figure 7–2.The TDM technique can be used with a TDM factor of 2, i.e., n = 2, to
implement this filter using only four multipliers, provided the filter is
clocked two times faster internally.
To understand this concept, consider
Figure 7–7 that shows a TDM filter
with a TDM factor of 2. A 2
× -multiplied clock is required to run the filter.
On cycle 0 of the 2
× clock, the user loads four coefficients into the four
multiplier inputs. The resulting output is stored in a register. On cycle 1
of the 2
× clock, the user loads the remaining four coefficients into the
multiplier inputs. The output of cycle 1 is added with the output of cycle
page 7–14 section for details on the coefficient loading schedule.
The TDM implementation shown in
Figure 7–7 requires only four
multipliers to achieve the functionality of an 8-tap filter. Thus, TDM is a
good way to save logic resources, provided the multipliers can run at n-
times the clock speed. The coefficients can be stored in ROM/RAM, or
any other muxing scheme.
Table 7–6. Basic FIR Filter Implementation Results
Part
EP1S10F780
Utilization
LCELL: 130/10570 (1%)
DSP Block 9-bit elements: 16/48 (33%)
Memory bits: 288/920448 (<1%)
Performance
247 MHz