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https://github.com/sehugg/8bitworkshop.git
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274 lines
7.1 KiB
Verilog
274 lines
7.1 KiB
Verilog
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`include "hvsync_generator.v"
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`include "sprite_bitmap.v"
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`include "sprite_renderer.v"
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`include "cpu8.v"
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/*
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A simple racing game with two sprites and a scrolling playfield.
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This version uses the 8-bit CPU.
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*/
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module racing_game_cpu_top(clk, reset, hsync, vsync, hpaddle, vpaddle, rgb);
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input clk, reset;
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input hpaddle, vpaddle;
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output hsync, vsync;
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wire display_on;
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wire [8:0] hpos;
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wire [8:0] vpos;
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output [3:0] rgb;
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parameter PADDLE_X = 0; // paddle X coordinate
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parameter PADDLE_Y = 1; // paddle Y coordinate
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parameter PLAYER_X = 2; // player X coordinate
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parameter PLAYER_Y = 3; // player Y coordinate
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parameter ENEMY_X = 4; // enemy X coordinate
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parameter ENEMY_Y = 5; // enemy Y coordinate
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parameter ENEMY_DIR = 6; // enemy direction (1, -1)
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parameter SPEED = 7; // player speed
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parameter TRACKPOS_LO = 8; // track position (lo byte)
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parameter TRACKPOS_HI = 9; // track position (hi byte)
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parameter IN_HPOS = 8'h40; // CRT horizontal position
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parameter IN_VPOS = 8'h41; // CRT vertical position
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// flags: [0, 0, collision, vsync, hsync, vpaddle, hpaddle, display_on]
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parameter IN_FLAGS = 8'h42;
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reg [7:0] ram[0:15]; // 16 bytes of RAM
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reg [7:0] rom[0:127]; // 128 bytes of ROM
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wire [7:0] address_bus; // CPU address bus
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reg [7:0] to_cpu; // data bus to CPU
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wire [7:0] from_cpu; // data bus from CPU
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wire write_enable; // write enable bit from CPU
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// 8-bit CPU module
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CPU cpu(.clk(clk),
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.reset(reset),
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.address(address_bus),
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.data_in(to_cpu),
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.data_out(from_cpu),
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.write(write_enable));
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// RAM write from CPU
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always @(posedge clk)
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if (write_enable)
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ram[address_bus[3:0]] <= from_cpu;
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// RAM read from CPU
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always @(*)
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casez (address_bus)
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// RAM
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8'b00??????: to_cpu = ram[address_bus[3:0]];
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// special read registers
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IN_HPOS: to_cpu = hpos[7:0];
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IN_VPOS: to_cpu = vpos[7:0];
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IN_FLAGS: to_cpu = {2'b0, frame_collision,
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vsync, hsync, vpaddle, hpaddle, display_on};
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// ROM
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8'b1???????: to_cpu = rom[address_bus[6:0]];
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default: to_cpu = 8'bxxxxxxxx;
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endcase
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// sync generator module
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hvsync_generator hvsync_gen(
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.clk(clk),
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.reset(0),
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.hsync(hsync),
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.vsync(vsync),
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.display_on(display_on),
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.hpos(hpos),
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.vpos(vpos)
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);
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// flags for player sprite renderer module
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wire player_vstart = {1'b0,ram[PLAYER_Y]} == vpos;
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wire player_hstart = {1'b0,ram[PLAYER_X]} == hpos;
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wire player_gfx;
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wire player_is_drawing;
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// flags for enemy sprite renderer module
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wire enemy_vstart = {1'b0,ram[ENEMY_Y]} == vpos;
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wire enemy_hstart = {1'b0,ram[ENEMY_X]} == hpos;
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wire enemy_gfx;
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wire enemy_is_drawing;
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// select player or enemy access to ROM
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wire player_load = (hpos >= 256) && (hpos < 260);
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wire enemy_load = (hpos >= 260);
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// wire up car sprite ROM
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// multiplex between player and enemy ROM address
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wire [3:0] player_sprite_yofs;
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wire [3:0] enemy_sprite_yofs;
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wire [3:0] car_sprite_yofs = player_load ? player_sprite_yofs : enemy_sprite_yofs;
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wire [7:0] car_sprite_bits;
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car_bitmap car(
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.yofs(car_sprite_yofs),
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.bits(car_sprite_bits));
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// player sprite renderer
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sprite_renderer player_renderer(
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.clk(clk),
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.vstart(player_vstart),
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.hstart(player_hstart),
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.load(player_load),
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.rom_addr(player_sprite_yofs),
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.rom_bits(car_sprite_bits),
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.gfx(player_gfx),
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.in_progress(player_is_drawing));
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// enemy sprite renderer
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sprite_renderer enemy_renderer(
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.clk(clk),
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.vstart(enemy_vstart),
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.hstart(enemy_hstart),
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.load(enemy_load),
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.rom_addr(enemy_sprite_yofs),
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.rom_bits(car_sprite_bits),
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.gfx(enemy_gfx),
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.in_progress(enemy_is_drawing));
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// collision detection logic
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reg frame_collision;
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always @(posedge clk)
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if (player_gfx && (enemy_gfx || track_gfx))
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frame_collision <= 1;
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else if (vpos==0)
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frame_collision <= 0;
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// track graphics
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wire track_offside = (hpos[7:5]==0) || (hpos[7:5]==7);
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wire track_shoulder = (hpos[7:3]==3) || (hpos[7:3]==28);
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wire track_gfx = (vpos[5:1]!=ram[TRACKPOS_LO][5:1]) && track_offside;
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// RGB output
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wire r = display_on && (player_gfx || enemy_gfx || track_shoulder);
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wire g = display_on && (player_gfx || track_gfx);
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wire b = display_on && (enemy_gfx || track_shoulder);
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assign rgb = {1'b0,b,g,r};
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//////////// CPU program code
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`ifdef EXT_INLINE_ASM
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initial begin
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rom = '{
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__asm
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.arch femto8 ; FEMTO-8 architecture
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.org 128 ; origin = 128 ($80)
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.len 128 ; length = 128 ($80)
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; define constants
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.define PADDLE_X 0
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.define PADDLE_Y 1
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.define PLAYER_X 2
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.define PLAYER_Y 3
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.define ENEMY_X 4
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.define ENEMY_Y 5
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.define ENEMY_DIR 6
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.define SPEED 7
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.define TRACKPOS_LO 8
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.define TRACKPOS_HI 9
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.define IN_HPOS $40
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.define IN_VPOS $41
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.define IN_FLAGS $42
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.define F_DISPLAY 1
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.define F_HPADDLE 2
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.define F_VPADDLE 4
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.define F_HSYNC 8
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.define F_VSYNC 16
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.define F_COLLIDE 32
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Start:
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lda #128 ; load initial positions
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sta PLAYER_X ; player_x = 128
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sta ENEMY_X ; enemy_x = 128
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sta ENEMY_Y ; enemy_y = 128
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lda #180
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sta PLAYER_Y ; player_y = 180
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zero A
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sta SPEED ; player speed = 0
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inc A
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sta ENEMY_DIR ; enemy dir = 1 (right)
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; read horizontal paddle position
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DisplayLoop:
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lda #F_HPADDLE ; paddle flag -> A
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ldb #IN_FLAGS ; addr of IN_FLAGS -> B
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and none,[B] ; read B, AND with A
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bz DisplayLoop ; loop until paddle flag set
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ldb #IN_VPOS
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mov A,[B] ; load vertical position -> A
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sta PLAYER_X ; store player x position
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; wait for vsync
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lda #F_VSYNC
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ldb #IN_FLAGS
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WaitForVsyncOn:
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and none,[B]
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bz WaitForVsyncOn ; wait until VSYNC on
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WaitForVsyncOff:
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and none,[B]
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bnz WaitForVsyncOff ; wait until VSYNC off
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; check collision
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lda #F_COLLIDE
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ldb #IN_FLAGS
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and none,[B] ; collision flag set?
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bz NoCollision ; skip ahead if not
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lda #16
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sta SPEED ; speed = 16
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NoCollision:
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; update speed
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ldb #SPEED
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mov A,[B] ; speed -> A
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inc A ; increment speed
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bz MaxSpeed ; speed wraps to 0?
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sta SPEED ; no, store speed
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MaxSpeed:
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mov A,[B] ; reload speed -> A
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lsr A
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lsr A
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lsr A
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lsr A ; divide speed by 16
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; add to lo byte of track pos
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ldb #TRACKPOS_LO
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add B,[B] ; B <- speed/16 + trackpos_lo
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swapab ; swap A <-> B
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sta TRACKPOS_LO ; A -> trackpos_lo
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swapab ; swap A <-> B again
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bcc NoCarry ; carry flag from earlier add op
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; add to hi byte of track pos
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ldb #TRACKPOS_HI
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mov B,[B] ; B <- trackpos_hi
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inc b ; increment B
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swapab ; swap A <-> B
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sta TRACKPOS_HI ; A -> trackpos_hi
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swapab ; swap A <-> B again
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NoCarry:
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; update enemy vert pos
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ldb #ENEMY_Y
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add A,[B]
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sta ENEMY_Y ; enemy_y = enemy_y + speed/16
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; update enemy horiz pos
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ldb #ENEMY_X
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mov A,[B]
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ldb #ENEMY_DIR
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add A,[B]
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sta ENEMY_X ; enemy_x = enemy_x + enemy_dir
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sub A,#64
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and A,#127 ; A <- (enemy_x-64) & 127
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bnz SkipXReverse ; skip if enemy_x is in range
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; load ENEMY_DIR and negate
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zero A
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sub A,[B]
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sta ENEMY_DIR ; enemy_dir = -enemy_dir
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SkipXReverse:
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; back to display loop
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jmp DisplayLoop
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__endasm
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};
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end
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`endif
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endmodule
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