Need help with timing in Verilog functions

Question

I'm doing a filtering project and I'm writing a module that feeds a lot of data to some compute units. There's a lot of really repetitive code and I was wondering if there was any way to condense it, like a task or a function.

I looked into it though and it seems that tasks are non-synthesizable but allow for timing constraints. Usually used in simulation and testbenches. Functions are synthesizable but do not allow timing constraints.

case(row_count) 
        
            0: begin //row_count = 0 means in between frames
                pixel_address <= 0;
                pixel_value <= 0;
                pixel_valid <= 0;
                minion0_select <= 0;
                minion1_select <= 0;
                minion2_select <= 0;
                byte_count <= 0;
                target_row <= 0;
            end
            
            1: begin //greyscale_valid has gone high for the first time in the frame
                minion0_select <= 1; //select minion 1
                minion0_target <= 0; //set minion0 to compute row 0
                case(greyscale_valid)
                    0: begin
                        pixel_address <= 0;
                        pixel_value <= 0;
                        pixel_valid <= 0;
                    end
                    1: begin //send the data until greyscale_valid is deasserted
                        case(fsm_state) 
                            s0_default: begin
                                pixel_address <= byte_count * 8;
                                pixel_value <= greyscale_value;
                                pixel_valid <= 1;
                                fsm_state <= s1_timer;
                                count <= 7;
                            end
                            s1_timer: begin
                                count <= (count == 0) ? 0:(count-1);
                                fsm_state <= (count == 0) ? s0_default:s1_timer;
                                byte_count <= (count == 0) ? (byte_count + 1):byte_count;
                            end
                        endcase
                    end
                endcase
            end
            
            2: begin //greyscale_valid has gone high for the second time in the frame
                minion1_select <= 1; //minion0 is already selected, select minion1 as well
                minion1_target <= 1; //set minion1 to compute row 1
                case(greyscale_valid)
                    0: begin
                        pixel_address <= 0;
                        pixel_value <= 0;
                        pixel_valid <= 0;
                    end
                    1: begin //send the data until greyscale_valid is deasserted
                        case(fsm_state) 
                            s0_default: begin
                                pixel_address <= byte_count * 8;
                                pixel_value <= greyscale_value;
                                pixel_valid <= 1;
                                fsm_state <= s1_timer;
                                count <= 7;
                            end
                            s1_timer: begin
                                count <= (count == 0) ? 0:(count-1);
                                fsm_state <= (count == 0) ? s0_default:s1_timer;
                                byte_count <= (count == 0) ? (byte_count + 1):byte_count;
                            end
                        endcase
                    end
                endcase
            end
            
            3: begin //greyscale_valid has gone high for the third time in the frame
                minion2_select <= 1; //select minion2, all minions currently receiving data
                case(greyscale_valid)
                    0: begin
                        pixel_address <= 0;
                        pixel_value <= 0;
                        pixel_valid <= 0;
                    end
                    1: begin //send the data until greyscale_valid is deasserted
                        case(fsm_state) 
                            s0_default: begin
                                pixel_address <= byte_count * 8;
                                pixel_value <= greyscale_value;
                                pixel_valid <= 1;
                                fsm_state <= s1_timer;
                                count <= 7;
                            end
                            s1_timer: begin
                                count <= (count == 0) ? 0:(count-1);
                                fsm_state <= (count == 0) ? s0_default:s1_timer;
                                byte_count <= (count == 0) ? (byte_count + 1):byte_count;
                            end
                        endcase
                    end
                endcase
            end
        
            
        endcase
endcase

It's pretty much just that case statement case(greyscale_valid). Any help would be appreciated!

Answer 1

I would move the case grayscale_valid completely outside (and after) the case row_count.

Wrap the case grayscale_valid in if (row_count > 0) so it only gets executed when row_count is not zero.