Index 2 out of range [1:0] out_sin_buf_taylor

[bonnom]

I like the code!

Is there a mistake at the lines '214' and '275' of dds.sv?

always_ff @(posedge clk) begin
       integer k;
       for (k = 0; k < TAYLOR_OUT_PIPELINE_STAGES; k = k + 1) begin

Shouldn't it be:

always_ff @(posedge clk) begin
integer k;
       for (k = 0; k < TAYLOR_OUT_PIPELINE_STAGES-1; k = k + 1) begin 

Otherwise it doesn't make sense with:

reg signed [OUT_DW - 1 : 0] out_sin_buf_taylor[TAYLOR_PIPELINE_STAGES - 2 : 0];
reg signed [OUT_DW - 1 : 0] out_cos_buf_taylor[TAYLOR_PIPELINE_STAGES - 2 : 0]; 

Since otherwise the index goes out of range!

[catkira]

Hi,
I think it does not go out of range because there is an if around the assignment

 else if (k < TAYLOR_PIPELINE_STAGES -1) begin  // stages 6-7
                    out_sin_buf_taylor[k]           <= out_sin_buf_taylor[k-1];

[bonnom]

Yes you are correct, except for the if(!reset_n) part.

It seems that some synthesize software doesn't like it if index goes out of range for !reset_n
Probably most synthesize tools recognize it is a reset, so they don't bother that it goes out of range.

        integer k;
        for (k = 0; k < TAYLOR_PIPELINE_STAGES; k = k + 1) begin
            if (!reset_n) begin
                out_sin_buf_taylor[k] <= '0;
                out_cos_buf_taylor[k] <= '0;
                sin_extended[k] <= '0;
                cos_extended[k] <= '0;
                phase_error_multiplied_buf[k] <= '0;
                phase_error_multiplied_buf2[k] <= '0;
                valid_taylor[k] <= '0;
            end else begin
                if(k == 0) begin

[catkira]

yes u r right. The code could be a bit cleaned up in general. PRs are welcome :)