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`timescale 1ns / 1ps
module line_buffer #(
parameter DATA_WIDTH=8,
parameter IMAGE_SIZE=5,
parameter NUM_LINES=3,
parameter PADDING=1
)(
input wire clk,
input wire rst,
input wire pixel_valid,
input wire [DATA_WIDTH-1:0] pixel_in,
output wire [DATA_WIDTH*NUM_LINES*NUM_LINES-1:0] window,
output reg window_valid
);
localparam IMAGE_SIZE_PADDED = IMAGE_SIZE+2*PADDING;
localparam FIFO_DEPTH = IMAGE_SIZE * IMAGE_SIZE;
// Padding registers
reg [$clog2(IMAGE_SIZE_PADDED)-1:0] col_count_pad;
reg [$clog2(IMAGE_SIZE_PADDED)-1:0] row_count_pad;
reg [DATA_WIDTH-1:0] fifo [0:FIFO_DEPTH-1];
reg [$clog2(FIFO_DEPTH)-1:0] write_ptr;
reg [$clog2(FIFO_DEPTH)-1:0] read_ptr;
reg fifo_empty;
reg is_padding;
// Padded pixel output
reg [DATA_WIDTH-1:0] padded_pixel;
reg padded_pixel_valid;
// Line buffer registers
reg [DATA_WIDTH-1:0] line_buf [0:NUM_LINES-1][0:IMAGE_SIZE_PADDED-1];
reg [DATA_WIDTH-1:0] window_bufs [0:NUM_LINES-1][0:NUM_LINES-1];
reg [$clog2(IMAGE_SIZE_PADDED)-1:0] buf_ptr;
reg [$clog2(NUM_LINES)-1:0] row_count;
reg [$clog2(IMAGE_SIZE*IMAGE_SIZE):0] window_count;
reg frame_complete;
integer i, j;
// Padding logic
always @(*) begin
if (PADDING) begin
is_padding = (row_count_pad == 0) || (row_count_pad == IMAGE_SIZE_PADDED-1) ||
(col_count_pad == 0) || (col_count_pad == IMAGE_SIZE_PADDED-1);
if (!is_padding) begin
padded_pixel = fifo[read_ptr];
padded_pixel_valid = !fifo_empty;
end else begin
padded_pixel = 0;
padded_pixel_valid = pixel_valid;
end
end else begin
padded_pixel = pixel_in;
padded_pixel_valid = pixel_valid;
end
end
// FIFO and counter
always @(posedge clk) begin
if (rst) begin
col_count_pad <= 0;
row_count_pad <= 0;
write_ptr <= 0;
read_ptr <= 0;
fifo_empty <= 1'b1;
end else if (PADDING) begin
if (pixel_valid) begin
fifo[write_ptr] <= pixel_in;
write_ptr <= (write_ptr == FIFO_DEPTH-1) ? 0 : write_ptr + 1;
fifo_empty <= 1'b0;
end
if (!is_padding && !fifo_empty) begin
read_ptr <= (read_ptr == FIFO_DEPTH-1) ? 0 : read_ptr + 1;
fifo_empty <= (read_ptr + 1 == write_ptr);
end
if (col_count_pad == IMAGE_SIZE_PADDED-1) begin
col_count_pad <= 0;
row_count_pad <= (row_count_pad == IMAGE_SIZE_PADDED-1) ? 0 : row_count_pad + 1;
end else begin
col_count_pad <= col_count_pad + 1;
end
end
end
// Line buffer shifting
always @(posedge clk) begin
if (rst) begin
buf_ptr <= 0;
row_count <= 0;
window_valid <= 0;
window_count <= 0;
frame_complete <= 0;
end else begin
for (i=NUM_LINES-1; i>0; i=i-1) begin
line_buf[i][buf_ptr] <= line_buf[i-1][buf_ptr];
end
line_buf[0][buf_ptr] <= padded_pixel;
if (buf_ptr == IMAGE_SIZE_PADDED-1) begin
buf_ptr <= 0;
row_count <= (row_count == NUM_LINES) ? row_count : row_count + 1;
end else begin
buf_ptr <= buf_ptr + 1;
end
window_valid <= (!frame_complete && row_count == NUM_LINES && buf_ptr >= NUM_LINES-1) ? 1 : 0;
if (window_valid) begin
if (window_count == (IMAGE_SIZE*IMAGE_SIZE)-1) begin
window_valid <= 0;
window_count <= 0;
frame_complete <= 1;
end else begin
window_count <= window_count + 1;
end
end
end
end
// Window buffer shifting
always @(posedge clk) begin
if (rst) begin
for (i=0; i<NUM_LINES; i=i+1) begin
for (j=0; j<NUM_LINES; j=j+1) begin
window_bufs[i][j] <= 0;
end
end
end else begin
for (i=0; i<NUM_LINES; i=i+1) begin
window_bufs[i][NUM_LINES-1] <= line_buf[i][buf_ptr];
for (j=NUM_LINES-1; j>0; j=j-1) begin
window_bufs[i][j-1] <= window_bufs[i][j];
end
end
end
end
// Window output generation
generate
genvar k, l;
for (k=0; k<NUM_LINES; k=k+1) begin
for (l=0; l<NUM_LINES; l=l+1) begin
assign window[((NUM_LINES-1-k)*NUM_LINES+l)*DATA_WIDTH+:DATA_WIDTH] = window_bufs[k][l];
end
end
endgenerate
endmodule
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