Indentation and alignment

Indentation

• All indents must be in 4 space increments.

An example is shown below.

always_comb begin
    if(enable_1)
        if(enable_2)
            data = 1'b1;
        else
            data = 1'b0;
    else
        if(enable_3)
            data = 1'b0;
        else
            data = 1'b1;
end

Warning

“tab” and “4 spaces” look very similar, but don’t use tab instead of 4 spaces.

Some editors have automatically replaced the tab key with 4 spaces.

• Each sub code block must be indented one level.

These are a few examples.

module pipe (
    // IO is a sub code block for module
    input           clk     ,
    input           rst_n   ,
    input           din0    ,
    input           din1    ,
    output logic    dout0   ,
    output logic    dout1
);
    // RTL content is a sub code block for module
    always_ff @(posedge clk or negedge rst_n) begin

        //if-else is a sub code block for always
        if(rst_n) begin

            // this is a sub code block for if-else
            dout0 <= 1'b0;
            dout1 <= 1'b0;
        end
        else begin
            dout0 <= din0;
            dout1 <= din1;
        end
    end

    // In fact, begin ... end form a sub block, but by convention,
    // "begin" can be left alone, "end" is new but not indented,
    // and the rest of the sub block code must be new and indented.

endmodule

Alignment

In general, variable names, operators, keywords, etc. should be aligned in several lines with similar functions, as shown in the following examples.

assign res0  = din0  + din1    ;
assign res32 = din45 + din235  ;

always_comb begin
    out_en  = in_en  ;
    out_pld = in_pld ;
end

input               out_ready   ,
output logic        out_valid   ,
output logic [31:0] out_payload ,

reg_slice u_rs (
    .clk         (clk         ),
    .rst_n       (rst_n       ),
    .in_valid    (in_valid    ),
    .in_ready    (in_ready    ),
    .in_payload  (in_payload  ),
    .out_valid   (out_valid   ),
    .out_ready   (out_ready   ),
    .out_payload (out_payload )
);