ℹ️ Select 'Choose Exercise', or randomize 'Next Random Exercise' in selected language.

Choose Exercise:
Timer 00:00
WPM --
Score --
Acc --
Correct chars --

Verilog Pipeline Scheduler for Task Execution

Verilog

Goal -- WPM

Ready
Exercise Algorithm Area
1module pipeline_scheduler (
2input wire clk,
3input wire reset,
4
5// Task input signals
6input wire task_valid_in,
7input wire [7:0] task_data_in,
8output wire task_ready_out,
9
10// Stage control signals
11output wire fetch_enable,
12output wire decode_enable,
13output wire execute_enable,
14
15// Data output
16output wire [7:0] result_data_out,
17output wire result_valid_out
18);
19
20// Pipeline registers
21logic task_valid_reg1, task_valid_reg2, task_valid_reg3;
22logic [7:0] task_data_reg1, task_data_reg2, task_data_reg3;
23logic result_valid_reg;
24logic [7:0] result_data_reg;
25
26// Dependency detection signals
27logic decode_hazards, execute_hazards;
28
29// Stage enable signals
30assign fetch_enable = task_valid_in && task_ready_out;
31assign decode_enable = task_valid_reg1 && !decode_hazards;
32assign execute_enable = task_valid_reg2 && !execute_hazards;
33
34// Output assignments
35assign task_ready_out = !task_valid_reg1 || decode_hazards;
36assign result_data_out = result_data_reg;
37assign result_valid_out = result_valid_reg;
38
39// Pipeline register updates
40always @(posedge clk or posedge reset) begin
41if (reset) begin
42task_valid_reg1 <= 1'b0;
43task_data_reg1 <= 8'b0;
44task_valid_reg2 <= 1'b0;
45task_data_reg2 <= 8'b0;
46task_valid_reg3 <= 1'b0;
47task_data_reg3 <= 8'b0;
48result_valid_reg <= 1'b0;
49result_data_reg <= 8'b0;
50end else begin
51// Stage 1: Fetch to Decode
52if (fetch_enable) begin
53task_valid_reg1 <= task_valid_in;
54task_data_reg1 <= task_data_in;
55end else if (!task_ready_out) begin // Stall
56task_valid_reg1 <= task_valid_reg1;
57task_data_reg1 <= task_data_reg1;
58end else begin // Bubble
59task_valid_reg1 <= 1'b0;
60task_data_reg1 <= 8'b0;
61end
62
63// Stage 2: Decode to Execute
64if (decode_enable) begin
65task_valid_reg2 <= task_valid_reg1;
66task_data_reg2 <= task_data_reg1;
67end else if (!task_ready_out && task_valid_reg1) begin // Stall
68task_valid_reg2 <= task_valid_reg2;
69task_data_reg2 <= task_data_reg2;
70end else begin // Bubble
71task_valid_reg2 <= 1'b0;
72task_data_reg2 <= 8'b0;
73end
74
75// Stage 3: Execute to Result
76if (execute_enable) begin
77task_valid_reg3 <= task_valid_reg2;
78task_data_reg3 <= task_data_reg2;
79end else if (!task_ready_out && task_valid_reg2) begin // Stall
80task_valid_reg3 <= task_valid_reg3;
81task_data_reg3 <= task_data_reg3;
82end else begin // Bubble
83task_valid_reg3 <= 1'b0;
84task_data_reg3 <= 8'b0;
85end
86
87// Result register update
88if (execute_enable) begin
89result_valid_reg <= task_valid_reg3;
90result_data_reg <= task_data_reg3; // Simplified execution
91end else begin
92result_valid_reg <= 1'b0;
93result_data_reg <= 8'b0;
94end
95end
96end
97
98// Simplified hazard detection (e.g., RAW dependency on previous instruction)
99// In a real system, this would be more complex, checking against register file state.
100// For this example, assume a hazard if the previous stage has data and is not ready.
101assign decode_hazards = task_valid_reg1 && task_valid_reg2;
102assign execute_hazards = task_valid_reg2 && task_valid_reg3;
103
104endmodule
Algorithm description viewbox

Verilog Pipeline Scheduler for Task Execution

Algorithm description:

This Verilog module implements a basic three-stage pipeline scheduler for task execution. It manages data flow through Fetch, Decode, and Execute stages, including rudimentary hazard detection to stall the pipeline. This design is crucial for improving instruction throughput in processors and other sequential processing systems.

Algorithm explanation:

The pipeline scheduler uses three stages: Fetch, Decode, and Execute, with registers between each stage to hold intermediate data and validity signals. The `task_ready_out` signal indicates if the pipeline can accept new tasks, which is asserted when the first stage is ready or if there's a hazard preventing further advancement. Hazard detection (`decode_hazards`, `execute_hazards`) is simplified here; in a real CPU, this would involve checking register file dependencies. When a hazard is detected, the pipeline stalls by not advancing the valid signals and data through the affected stages. Bubbles (invalid data) are introduced when a stage is not enabled. The space complexity is O(1) as the number of registers is fixed by the pipeline depth. The time complexity for a task to pass through the pipeline is O(N) where N is the number of stages, but the throughput can approach O(1) per cycle in the absence of hazards.

Pseudocode:

Define pipeline stages: Fetch, Decode, Execute.
Define pipeline registers for valid bits and data for each stage.

On positive clock edge or positive reset:
  If reset:
    Clear all pipeline registers.
  Else:
    // Update Fetch stage register based on input and pipeline readiness.
    // If pipeline stalls, hold current values.
    // If no input and no stall, introduce a bubble.

    // Update Decode stage register based on Fetch stage output and hazards.
    // If Decode stage is enabled and no hazards:
    //   Move data from Fetch register to Decode register.
    // Else if pipeline stalls and Fetch stage has data:
    //   Hold Decode register values.
    // Else (bubble):
    //   Clear Decode register.

    // Update Execute stage register based on Decode stage output and hazards.
    // Similar logic to Decode stage update.

    // Update result register based on Execute stage output.

Determine pipeline readiness (task_ready_out) based on Fetch stage readiness and hazards.
Determine hazard conditions (e.g., RAW dependencies between stages).