bit_count.md

bit_count

Property	Value
Kind	module
RTL source	rtl/base/bit_ops.sv
Availability	Synthesizable RTL

Summary

Combinational population-count primitive.

Functional Behavior

Combinational population-count primitive. It is a self-contained base primitive with the behavior and parameter checks implemented in the linked RTL source.

Suitable Applications

Use as a structured building block for control, encoding, ECC, hashing, masking, replacement, or observability logic.

Parameters

The declaration below is canonical; retain the RTL-enforced parameter range.

Parameter	Declaration
WIDTH	parameter int WIDTH = 32
COUNT_WIDTH	parameter int COUNT_WIDTH = $clog2(WIDTH + 1)

Interface Definition

module bit_count #(
    parameter int WIDTH       = 32,
    parameter int COUNT_WIDTH = $clog2(WIDTH + 1)
) (
    input  logic [      WIDTH-1:0] value_i,
    output logic [COUNT_WIDTH-1:0] count_o
);

Port Summary

Signal	Direction	Declaration
value_i	input	input logic [ WIDTH-1:0] value_i
count_o	output	output logic [COUNT_WIDTH-1:0] count_o

Integration and Use

Honor validity/error outputs and parameter constraints. Combinational cells do not provide timing isolation or CDC protection.

bit_count #(
    .WIDTH(WIDTH),
    .COUNT_WIDTH(COUNT_WIDTH)
) u_bit_count (
    .value_i(value_i),
    .count_o(count_o)
);

Dependencies and Verification

The linked RTL source is the implementation authority and contains local assertions for unsupported parameter combinations. See docs/design.md for repository-wide CDC, reset, stream, and storage contracts, and docs/verification.md for the verification matrix.