Intel Agilex® 7 Variable Precision DSP Blocks User Guide

ID 683037
Date 4/11/2023
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2.1.7. Accumulator, Chainout Adder, and Preload Constant for Fixed-point Arithmetic

The Intel® Agilex™ 7 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
  • DISABLE_CHAINOUT

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

Table 7.   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