Design Considerations; Operational Modes; Internal Coefficient And Pre-Adder; Accumulator - Altera Cyclone V Device Handbook

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Design Considerations

You should consider the following elements in your design:

Operational Modes

The Quartus II software includes megafunctions that you can use to control the operation mode of the

multipliers. After entering the parameter settings with the MegaWizard Plug-In Manager, the Quartus II

software automatically configures the variable precision DSP block.

Altera provides two methods for implementing various modes of the Cyclone V variable precision DSP

block in a design—using the Quartus II DSP megafunction and HDL inferring.

The following Quartus II megafunctions are supported for the Cyclone V variable precision DSP blocks

implementation:

ALTMULT_ACCUM

ALTMULT_COMPLEX

Related Information

Introduction to Megafunction User Guide

Integer Arithmetic Megafunctions User Guide

Floating-Point Megafunctions User Guide

Quartus II Software Help

Internal Coefficient and Pre-Adder

To use the pre-adder feature, all input data and multipliers must have the same clock setting.

The input cascade support is not available when you enable the pre-adder feature.

In both 18-bit and 27-bit modes, you can use the coefficient feature and pre-adder feature independently.

The accumulator in the Cyclone V devices supports double accumulation by enabling the 64-bit double

accumulation registers located between the output register bank and the accumulator.

The double accumulation registers are set statically in the programming file.

Chainout Adder

You can use the output chaining path to add results from other DSP blocks.

Altera Corporation

Variable Precision DSP Blocks in Cyclone V Devices

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