Stratix® 10 Variable Precision DSP Blocks User Guide

ID 683832
Date 7/08/2024
Public
Document Table of Contents

2.7. Accumulator, Chainout Adder, and Preload Constant for Fixed-Point Arithmetic

The Stratix® 10 variable precision DSP block supports accumulator and adder up to 64 bits for fixed-point arithmetic.

The following signals can dynamically control the function of the accumulator and the chainout adder:

  • NEGATE
  • LOADCONST
  • ACCUMULATE

The accumulator and chainout adder features are not available in two fixed-point arithmetic independent 18 x 19 modes.

Table 8.   Accumulator Functions and Dynamic Control Signals
Function Description NEGATE LOADCONST ACCUMULATE
Zeroing Disables the accumulator. 0 0 0
Preload The result is always added to the preload value. Only one bit of the 64-bit preload value can be “1”. You can use this function to round the DSP result to any position of the 64-bit result. 0 1 0
Accumulation Adds the current result to the previous accumulate result. 0 X 1
Decimation + Accumulation This function takes the current result, converts it into two’s complement, and adds it to the previous result. 1 X 1
Decimation + Chainout Adder This function takes the current result, converts it into two’s complement, and adds it to the output of previous DSP block. 1 0 0