flag handling

README.md

@@ -32,7 +32,7 @@ yayacemu [PATH_TO_YOUR_ROM]
 ### Todo
 - [x] Graphics
 - [x] Corax+ Required Instructions
-- [ ] Proper Flag Handling 
+- [x] Proper Flag Handling 
 - [ ] Working Input
 - [ ] More Instructions
 - [ ] Tetris Working Running
@@ -46,3 +46,4 @@ yayacemu [PATH_TO_YOUR_ROM]
 ![Chip 8 Logo Demo](https://github.com/nickorlow/yayacemu/blob/main/screenshots/chip8-logo.png?raw=true)
 ![IBM Logo Demo](https://github.com/nickorlow/yayacemu/blob/main/screenshots/ibm-logo.png?raw=true)
 ![CORAX+ Test Demo](https://github.com/nickorlow/yayacemu/blob/main/screenshots/corax.png?raw=true)
+![Flag Test Demo](https://github.com/nickorlow/yayacemu/blob/main/screenshots/flags.png?raw=true)

yayacemu.cpp

@@ -14,6 +14,7 @@
 
 #define SCREEN_WIDTH 64
 #define SCREEN_HEIGHT 32
+#define EMULATION_HZ 480
 
 FILE *rom_file;
 SDL_Window *window;
@@ -89,10 +90,10 @@ int main(int argc, char** argv) {
     contextp->commandArgs(argc, argv);
     Vyayacemu* top = new Vyayacemu{contextp};
     //while (!contextp->gotFinish()) {
-    for (int i = 0; i < 20000; i++) { 
+    for (int i = 0; i < 2000; i++) { 
         top->clk_in ^= 1;
         top->eval(); 
-        usleep(500);
+        usleep(1000000/EMULATION_HZ);
     }
     printf("TB     : Testbench has reached end of simulation. Pausing for 10 seconds before exiting");
     fflush(stdout);

yayacemu.sv

@@ -8,16 +8,22 @@ module yayacemu (
     wire [7:0] registers [0:15];
     logic [3:0] stack_pointer;
     wire [15:0] stack [0:15];
+    logic [7:0] delay_timer;
+    logic [7:0] sound_timer;
+    int cycle_counter;
 
     logic [15:0] index_reg;
     logic rom_ready;
     logic [15:0] program_counter;
 
     rom_loader rl (memory, rom_ready);
-    chip8_cpu cpu (memory, clk_in, vram, stack, index_reg, stack_pointer, registers, program_counter);
+    chip8_cpu cpu (memory, clk_in, vram, stack, index_reg, stack_pointer, registers, delay_timer, sound_timer, cycle_counter, program_counter);
     chip8_gpu gpu (vram);
 
     initial begin 
+        sound_timer = 0;
+        delay_timer = 0;
+        cycle_counter = 0;
         program_counter = 'h200;
         stack_pointer = 4'b0000;
         init_screen();
@@ -33,13 +39,20 @@ module chip8_cpu(
     output wire [15:0] index_reg,
     output wire [3:0] stack_pointer,
     output wire [7:0] registers [0:15],
+    output logic [7:0] delay_timer,
+    output logic [7:0] sound_timer,
+    output int cycle_counter,
     output wire [15:0] program_counter 
     );
 
     logic [15:0] opcode;
+
     logic [15:0] scratch;
     logic [15:0] scratch2;
 
+    logic [7:0] scratch_8;
+    logic [7:0] scratch_82;
+
     logic [31:0] x_cord;
     logic [31:0] y_cord;
     logic [7:0] size;
@@ -56,6 +69,14 @@ module chip8_cpu(
         $display("HW     : opcode is 0x%h (%b)", opcode, opcode);
         $display("HW     : PC %0d 0x%h", program_counter, program_counter);
 
+        // 480Hz / 8 = 60 Hz
+        if (cycle_counter % 8 == 0) begin
+            if (delay_timer > 0)
+                delay_timer--;
+            if (sound_timer > 0)
+                sound_timer--;
+        end
+
         casez(opcode)
             'h00E0: begin 
                 $display("HW     : INSTR CLS");
@@ -127,28 +148,57 @@ module chip8_cpu(
             end
             'h8??4: begin
                 $display("HW     : INSTR ADD Vx, Vy");
+                scratch_8 = registers[(opcode & 'h0F00) >> 8];
                 registers[(opcode & 'h0F00) >> 8] += registers[(opcode & 'h00F0) >> 4];
+                registers[15] = {7'b0000000, scratch_8 > registers[(opcode & 'h0F00) >> 8]};
             end
             'h8??5: begin
                 $display("HW     : INSTR SUB Vx, Vy");
+                scratch_8 = registers[(opcode & 'h0F00) >> 8];
                 registers[(opcode & 'h0F00) >> 8] -= registers[(opcode & 'h00F0) >> 4];
+                registers[15] = {7'b0000000, scratch_8 >= registers[(opcode & 'h0F00) >> 8]};
             end
             'h8??6: begin
                 $display("HW     : INSTR SHR Vx {, Vy}");
+                scratch_8 = registers[(opcode & 'h0F00) >> 8];
                 registers[(opcode & 'h0F00) >> 8] = registers[(opcode & 'h00F0) >> 4]>> 1;
+                registers[15] = {7'b0000000,  ((scratch_8 & 8'h01) == 8'h01)};
             end
             'h8??7: begin
                 $display("HW     : INSTR SUBN Vx, Vy");
+                scratch_8 = registers[(opcode & 'h00F0) >> 4];
+                scratch_82 = registers[(opcode & 'h0F00) >> 8];
                 registers[(opcode & 'h0F00) >> 8] = registers[(opcode & 'h00F0) >> 4] - registers[(opcode & 'h0F00) >> 8];
+                registers[15] = {7'b0000000, (scratch_8 >= scratch_82)};
             end
             'h8??E: begin
                 $display("HW     : INSTR SHL Vx {, Vy}");
+                scratch_8 = registers[(opcode & 'h0F00) >> 8];
                 registers[(opcode & 'h0F00) >> 8] = registers[(opcode & 'h00F0) >> 4]<< 1;
+
+                registers[15] = {7'b0000000, (scratch_8[7]) };
+            end
+            'h9??0: begin
+                $display("HW     : INSTR SNE Vx, Vy");
+                if (registers[(opcode & 'h00F0) >> 4] != registers[(opcode & 'h0F00) >> 8]) begin
+                    program_counter += 2;
+                end
             end
             'hA???: begin
                 $display("HW     : INSTR LD I, addr");
                 index_reg = (opcode & 'h0FFF);
             end
+            'hb???: begin
+                $display("HW     : INSTR JP V0, addr");
+                program_counter = {8'h00, registers[0]} + (opcode & 'h0FFF) - 2;
+            end
+            'hc???: begin
+                $display("HW     : RND Vx, addr");
+                // TODO: use a real RNG module, this is not synthesizeable
+                scratch = {$urandom()%256}[15:0];
+                scratch2 = (opcode & 'h00FF);
+                registers[(opcode & 'h0F00) >> 8] = scratch[7:0] & scratch2[7:0];
+            end
             'hD???: begin
                 $display("HW     : INSTR DRW Vx, Vy, nibble");
                 x_cord = {24'h000000, registers[(opcode & 'h0F00) >> 8]};
@@ -174,45 +224,58 @@ module chip8_cpu(
                         end 
                   end 
                 end
-        end
+            end
-                'hF?33: begin
+            'hF?07: begin
-                   $display("HW     : INSTR LD B, Vx"); 
+                $display("HW     : INSTR LD Vx, DT");
-                    scratch = {8'h00, registers[(opcode & 'h0F00) >> 8]};
+                registers[(opcode & 'h0F00) >> 8] = delay_timer;
-                    scratch2 = scratch % 10;
+            end
-                    memory[index_reg + 2] = scratch2[7:0];
+            'hF?15: begin
-                    scratch /= 10;
+                $display("HW     : INSTR LD DT, Vx");
-                    scratch2 = scratch % 10;
+               delay_timer =  registers[(opcode & 'h0F00) >> 8];
-                    memory[index_reg + 1] = scratch2[7:0];
+            end
-                    scratch /= 10;
+            'hF?18: begin
-                    scratch2 = scratch % 10;
+                $display("HW     : INSTR LD ST, Vx");
-                    memory[index_reg + 0] = scratch2[7:0];
+               sound_timer =  registers[(opcode & 'h0F00) >> 8];
-                end
+            end
-                'hF?55: begin
+            'hF?1E: begin
-                   $display("HW     : INSTR LD [I], Vx"); 
+                $display("HW     : INSTR ADD I, Vx");
-                    scratch = (opcode & 'h0F00) >> 8;
+                index_reg = index_reg + {8'h00, registers[(opcode & 'h0F00) >> 8]};
-                    for (i8 = 0; i8 <= scratch[7:0]; i8++) begin 
+            end
-                      scratch2 = index_reg + {8'h00, i8};
+            'hF?33: begin
-                      memory[scratch2[11:0]] = registers[i8[3:0]];
+               $display("HW     : INSTR LD B, Vx"); 
-                    end 
+                scratch = {8'h00, registers[(opcode & 'h0F00) >> 8]};
-                    index_reg++;
+                scratch2 = scratch % 10;
-                end
+                memory[index_reg + 2] = scratch2[7:0];
-                'hF?65: begin
+                scratch /= 10;
-                    $display("HW     : INSTR LD Vx, [I]");
+                scratch2 = scratch % 10;
-                    scratch = (opcode & 'h0F00) >> 8;
+                memory[index_reg + 1] = scratch2[7:0];
-                    for (i8 = 0; i8 <= scratch[7:0]; i8++) begin 
+                scratch /= 10;
-                      scratch2 = index_reg + {8'h00, i8};
+                scratch2 = scratch % 10;
-                      registers[i8[3:0]] = memory[scratch2[11:0]];
+                memory[index_reg + 0] = scratch2[7:0];
-                    end 
+            end
-                    index_reg++;
+            'hF?55: begin
-                end
+               $display("HW     : INSTR LD [I], Vx"); 
-                'hF?1E: begin
+                scratch = (opcode & 'h0F00) >> 8;
-                    $display("HW     : INSTR ADD I, Vx");
+                for (i8 = 0; i8 <= scratch[7:0]; i8++) begin 
-                    index_reg = index_reg + {8'h00, registers[(opcode & 'h0F00) >> 8]};
+                  scratch2 = index_reg + {8'h00, i8};
-                end
+                  memory[scratch2[11:0]] = registers[i8[3:0]];
+                end 
+                index_reg++;
+            end
+            'hF?65: begin
+                $display("HW     : INSTR LD Vx, [I]");
+                scratch = (opcode & 'h0F00) >> 8;
+                for (i8 = 0; i8 <= scratch[7:0]; i8++) begin 
+                  scratch2 = index_reg + {8'h00, i8};
+                  registers[i8[3:0]] = memory[scratch2[11:0]];
+                end 
+                index_reg++;
+            end
             default: $display("HW     : ILLEGAL INSTRUCTION");
         endcase
         
         program_counter += 2;
+        cycle_counter++;
     end
 endmodule