HC4GX15 Datasheet, PDF (32/668 Pages) Altera Corporation – HardCopy IV Device Handbook

3–2
Chapter 3: DSP Block Implementation in HardCopy IV Devices
DSP Operational Mode and Feature Support
An example of efficient logic area usage is evident when comparing the 18 × 18
independent multiplier implementation in Stratix IV devices using the dedicated DSP
block versus the implementation in HardCopy IV devices using HCells. If the
Stratix IV DSP function only calls for one 18 × 18 multiplier, the other three 18 × 18
multipliers and the DSP block's adder output block are not used, as shown in
Figure 3–1. In HardCopy IV devices, the HCell-based logic fabric that is not used for
DSP functions can be used to implement other combinational logic, adder, register,
and MLAB functions.
Figure 3–1. Stratix IV DSP Block versus HardCopy IV HCell 18 × 18-Bit Independent Multiplier Implementation
Stratix IV DSP Block
HardCopy IV HCell-Based Logic Fabric
Input
Registers
18 × 18
Multiplier
Output
Registers
Input
Registers
18 × 18
Multiplier
Output
Registers
18 × 18
Multiplier
Input
Registers
18 × 18
Multiplier
Adder/
Subtractor/
Accumulator
Block
Output
Registers
18 × 18
Multiplier
These elements are implemented
using HCell macros.
Unused logic area can
be used to perform other
logic functions.
Used portions of the block
Unused portions of the block
DSP Operational Mode and Feature Support
HardCopy IV devices support all Stratix IV DSP configurations (9 × 9, 12 × 12,
18 × 18, and 36 × 36 multipliers) and all Stratix IV DSP block features, such as
dynamic sign controls, dynamic addition/subtraction, dynamic rounding and
saturation, and dynamic input shift registers.
HardCopy IV devices use DSP HCell macros to implement all five operational modes
of the Stratix IV DSP block:
■ Independent Multiplier (9 × 9, 12 × 12, 18 × 18, 36 × 36)
■ Two-Multiplier Adder
■ Four-Multiplier Adder
■ Multiply Accumulate
■ Shift
HardCopy IV Device Handbook, Volume 1
© December 2008 Altera Corporation