Cyclone® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683375
Date 10/18/2023
Document Table of Contents

3.5.6. Accumulator and Chainout Adder

The Cyclone® V variable precision DSP block supports a 64-bit accumulator and a 64-bit adder.

The following signals can dynamically control the function of the accumulator:


The accumulator 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.

The accumulator and chainout adder features are not supported in two independent 18 x 19 modes and three independent 9 x 9 modes.

Table 16.   Accumulator Functions and Dynamic Control Signals This table lists the dynamic signals settings and description for each function. In this table, X denotes a "don't care" value.
Zeroing Disables the accumulator. 0 0 0
Preload Loads an initial value to the accumulator. Only one bit of the 64-bit preload value can be “1”. It can be used as rounding 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 This function takes the current result, converts it into two’s complement, and adds it to the previous result. 1 X 1