common/docs/reference/utils/regfield.md

regfield

Property	Value
Kind	module
RTL source	rtl/utils/regfield.sv
Availability	Synthesizable RTL

Summary

Masked register-field update primitive.

Functional Behavior

Masked register-field update primitive. Its exact parameters and ports are reproduced below from the implementation declaration.

Suitable Applications

Use as a small reusable datapath, state, coding, delay, or verification primitive.

Parameters

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

Parameter	Declaration
DATA_WIDTH	parameter DATA_WIDTH = 32
SW_ACS	parameter SW_ACS = "rw", // rw, ro, wo, w1c, w1s, w0c, rc
RST_VAL	parameter logic [DATA_WIDTH-1:0] RST_VAL = '0 // Reset value

Interface Definition

module regfield #(
    parameter                        DATA_WIDTH = 32,
    parameter                        SW_ACS     = "rw",  // rw, ro, wo, w1c, w1s, w0c, rc
    parameter logic [DATA_WIDTH-1:0] RST_VAL    = '0     // Reset value
) (
    input                         clk_i,
    input                         rst_n_i,
    // from sw, in case of rc, top connects rd pulse to sw_wen_i
    input                         sw_wen_i,
    input        [DATA_WIDTH-1:0] sw_wdata_i,
    // from hw: valid for hrw, hwo
    input                         hw_wen_i,
    input        [DATA_WIDTH-1:0] hw_wdata_i,
    // output to hw and reg rd
    output logic                  data_en_o,
    output logic [DATA_WIDTH-1:0] data_o
);

Port Summary

Signal	Direction	Declaration
clk_i	input	input clk_i
rst_n_i	input	input rst_n_i
sw_wen_i	input	input sw_wen_i
sw_wdata_i	input	input [DATA_WIDTH-1:0] sw_wdata_i
hw_wen_i	input	input hw_wen_i
hw_wdata_i	input	input [DATA_WIDTH-1:0] hw_wdata_i
data_en_o	output	output logic data_en_o
data_o	output	output logic [DATA_WIDTH-1:0] data_o

Integration and Use

Keep parameter values within RTL assertions and add required clocking, reset, or CDC protection at the caller boundary.

regfield #(
    .DATA_WIDTH(DATA_WIDTH),
    .SW_ACS(SW_ACS),
    .RST_VAL(RST_VAL)
) u_regfield (
    .clk_i(clk_i),
    .rst_n_i(rst_n_i),
    .sw_wen_i(sw_wen_i),
    .sw_wdata_i(sw_wdata_i),
    .hw_wen_i(hw_wen_i),
    .hw_wdata_i(hw_wdata_i),
    .data_en_o(data_en_o),
    .data_o(data_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.