diff options
| -rw-r--r-- | design/vga.v | 130 |
1 files changed, 91 insertions, 39 deletions
diff --git a/design/vga.v b/design/vga.v index e652ea6..b46dcbd 100644 --- a/design/vga.v +++ b/design/vga.v @@ -17,11 +17,11 @@ /* Non-wishbone */ input wire clock_25mhz, - output reg h_sync, - output reg v_sync, - output reg [2:0] red, - output reg [2:0] green, - output reg [2:0] blue + output wire h_sync, + output wire v_sync, + output wire [2:0] red, + output wire [2:0] green, + output wire [2:0] blue ); reg powered_on; @@ -156,18 +156,10 @@ $readmemb(FONT_FILE, font, 0, 128 * 16 - 1); end - wire [6:0] char_x; - wire [4:0] char_y; - wire [12:0] char_flat_idx; - wire [15:0] text_memory_field; - wire [7:0] char; - assign char_x = h_counter / 8; - assign char_y = v_counter / 16; - assign char_flat_idx = char_x + char_y * LINE_LENGTH; - assign text_memory_field = text_memory[char_flat_idx[12:1]]; - assign char = char_flat_idx[0] ? - text_memory_field[15:8] : text_memory_field[7:0]; + parameter FG_COLOR = {3'b010, 3'b111, 3'b101}; + parameter BG_COLOR = {3'b000, 3'b000, 3'b111}; + /* display this for non-ascii characters */ wire [0:7] replacement_char [0:16]; assign replacement_char[0] = 8'b00000000; assign replacement_char[1] = 8'b00011000; @@ -186,38 +178,90 @@ assign replacement_char[14] = 8'b00011000; assign replacement_char[15] = 8'b00000000; - wire [2:0] char_pixel_x; - wire [3:0] char_pixel_y; + wire [6:0] char_x; + wire [4:0] char_y; + wire [12:0] char_flat_idx; + assign char_x = h_counter / 8; + assign char_y = v_counter / 16; + assign char_flat_idx = char_x + char_y * LINE_LENGTH; + + /* + * hs[0], vs[0], fetched_memory_field, is_high_byte, char, char_pixel_x[0], + * char_pixel_y and display_on[0] get loaded first, then, one tick later, + * hs[1], vs[1], char_pixel_x[1], display_on[1], char_pixel_row, + * replacement_pixel_row and is_ascii_char get loaded and finally, another + * tick later, color gets loaded + */ + reg [2:0] hs; + reg [2:0] vs; + reg [15:0] fetched_memory_field; + reg is_high_byte; + reg [2:0] char_pixel_x [1:0]; + reg [3:0] char_pixel_y; + reg [1:0] display_on; + reg [0:7] char_pixel_row; + reg [0:7] replacement_pixel_row; + reg is_ascii_char; + reg [8:0] color; + + wire [7:0] char; + wire [0:7] pixel_row_to_use; wire pixel_on; - wire display_on; - assign char_pixel_x = h_counter % 8; - assign char_pixel_y = v_counter % 16; - /* Replace non-ASCII characters (i.e. chars with values above 127) */ - assign pixel_on = char[7] ? replacement_char[char_pixel_y][char_pixel_x] : - font[char[6:0] * 16 + char_pixel_y][char_pixel_x]; - assign display_on = h_stage == H_STAGE_ACTIVE_VIDEO && - v_stage == V_STAGE_ACTIVE_VIDEO; + assign char = is_high_byte ? fetched_memory_field[15:8] : + fetched_memory_field[7:0]; + assign pixel_row_to_use = is_ascii_char ? char_pixel_row : + replacement_pixel_row; + assign pixel_on = pixel_row_to_use[char_pixel_x[1]]; - parameter FG_COLOR = {3'b010, 3'b111, 3'b101}; - parameter BG_COLOR = {3'b000, 3'b000, 3'b111}; + /* Assign module's outputs */ + assign h_sync = hs[2]; + assign v_sync = vs[2]; + assign {red, green, blue} = color; always @ (posedge clock_25mhz) begin + /* Stuff, that gets loaded first */ if (h_stage == H_STAGE_SYNC) - h_sync <= H_POLARITY; + hs[0] <= H_POLARITY; else - h_sync <= ~H_POLARITY; + hs[0] <= ~H_POLARITY; if (v_stage == V_STAGE_SYNC) - v_sync <= V_POLARITY; + vs[0] <= V_POLARITY; else - v_sync <= ~V_POLARITY; + vs[0] <= ~V_POLARITY; + + fetched_memory_field <= text_memory[char_flat_idx[12:1]]; + is_high_byte <= char_flat_idx[0]; + + char_pixel_x[0] <= h_counter % 8; + char_pixel_y <= v_counter % 16; + + display_on[0] <= h_stage == H_STAGE_ACTIVE_VIDEO && + v_stage == V_STAGE_ACTIVE_VIDEO; + + /* Stuff, that gets loaded one tick later */ + hs[1] <= hs[0]; + vs[1] <= vs[0]; + + char_pixel_x[1] <= char_pixel_x[0]; + + display_on[1] <= display_on[0]; + + char_pixel_row <= font[char[6:0] * 16 + char_pixel_y]; + replacement_pixel_row <= replacement_char[char_pixel_y]; + + is_ascii_char <= ~char[7]; + + /* Stuff, that gets loaded another tick later */ + hs[2] <= hs[1]; + vs[2] <= vs[1]; if (!display_on) - {red, green, blue} <= 9'b0; + color <= 9'b0; else if (pixel_on) - {red, green, blue} <= FG_COLOR; + color <= FG_COLOR; else - {red, green, blue} <= BG_COLOR; + color <= BG_COLOR; end // always @ (posedge clock_25mhz) `ifdef SIMULATION @@ -227,9 +271,18 @@ powered_on_latched <= 0; ack <= 0; - h_sync <= ~H_POLARITY; - v_sync <= ~V_POLARITY; - {red, green, blue} <= 9'b0; + hs <= {3{~H_POLARITY}}; + vs <= {3{~V_POLARITY}}; + fetched_memory_field <= 16'b0; + is_high_byte <= 0; + char_pixel_x[0] <= 0; + char_pixel_x[1] <= 0; + char_pixel_y <= 0; + display_on <= 2'b0; + char_pixel_row <= 8'b0; + replacement_pixel_row <= 8'b0; + is_ascii_char <= 0; + color <= 9'b0; h_counter <= 0; h_stage <= H_STAGE_RB_OR_FP; @@ -239,4 +292,3 @@ end `endif endmodule // vga - |