Update README.md

Q bug?

.gitignore

@@ -2,3 +2,4 @@
 dumb8
 das
 *.bin
+examples/*.bin

README.md

@@ -1,8 +1,11 @@
 # Dumb8-CPU
 
+![image](dumb8.png)
+
 Continuing my exploration of the lower-level world...
 
 This project is the implementation of a CPU in a high-level language, C. It aims to have a reduced (minimalist) instruction set and still be Turing complete.
+In the future, I'd like to implement it in a hardware description language such as VHDL or Verilog. 
 
 ## How to test
 
@@ -20,7 +23,7 @@ make
 
 - 8-bit processing unit
 - RISC (reduced instruction set computer)
-- 4 general purpose registers (labeled R0 to R3)
+- 8 general purpose registers (labeled Rx)
 - 1 input port, 1 output port (via getchar and putchar)
 - Turing-completeness: bitwise and arithmetic operations
 
@@ -30,9 +33,14 @@ make
 ; Move register RY to register RX
 MOV RX, RY
 
-; Arithmetic addition and substraction stored in RX
+; Put value X in register RX
+PUT RX, X
+
+; Arithmetic operations. Result stored in RX
 ADD RX, RY
 SUB RX, RY
+MUL RX, RY
+DIV RX, RY
 
 ; Bitwise operations stored in RX
 OR RX, RY
@@ -64,4 +72,4 @@ HLT
 
 ## Known bugs
 
-- R0 is not usable (confusion with NOP opcode 0 in memory)
+- If you find one, please open an issue. Contributions are highly appreciated!

assembler/das.c

@@ -106,6 +106,24 @@ void assemble(char* filename)
 			buffer[i++] = reg1_n;
 			buffer[i++] = reg2_n;
 		}
+		else if (strncmp(line, "MUL", 3) == 0)
+		{
+			sscanf(line, "%s %[^,], %s", instruction, reg1, reg2);	
+			int reg1_n = reg1[1] - '0';
+			int reg2_n = reg2[1] - '0';
+			buffer[i++] = MUL;
+			buffer[i++] = reg1_n;
+			buffer[i++] = reg2_n;
+		}
+		else if (strncmp(line, "DIV", 3) == 0)
+		{
+			sscanf(line, "%s %[^,], %s", instruction, reg1, reg2);	
+			int reg1_n = reg1[1] - '0';
+			int reg2_n = reg2[1] - '0';
+			buffer[i++] = DIV;
+			buffer[i++] = reg1_n;
+			buffer[i++] = reg2_n;
+		}
 		else if (strncmp(line, "OR", 3) == 0)
 		{
 			sscanf(line, "%s %[^,], %s", instruction, reg1, reg2);	
@@ -135,10 +153,8 @@ void assemble(char* filename)
 		}
 		else if (strncmp(line, "JEQ", 3) == 0)
 		{
-			sscanf(line, "%s %[^,], %d", instruction, reg1, &addr);
-			int reg1_n = reg1[1] - '0';
+			sscanf(line, "%s %d", instruction, &addr);
 			buffer[i++] = JEQ;
-			buffer[i++] = reg1_n;
 			buffer[i++] = addr;
 		}
 		else if (strncmp(line, "JMP", 3) == 0)

cpu.c

@@ -26,6 +26,7 @@ void cpu_init()
 	cpu.halted = false;
 	cpu.equal_flag = false;
 	cpu.flag_clear_delay = 0;
+	cpu.increment = 0;
 	for (size_t i=0; i<NUM_REGISTERS; i++)
 	{
 		cpu.reg[i] = 0;
@@ -74,6 +75,16 @@ void cpu_exec(uint8_t opcode)
 			reg2 = cpu.memory[cpu.pc++];
 			cpu.reg[reg1] -= cpu.reg[reg2];
 			break;
+		case MUL:
+			reg1 = cpu.memory[cpu.pc++];
+			reg2 = cpu.memory[cpu.pc++];
+			cpu.reg[reg1] *= cpu.reg[reg2];
+			break;
+		case DIV:
+			reg1 = cpu.memory[cpu.pc++];
+			reg2 = cpu.memory[cpu.pc++];
+			cpu.reg[reg1] /= cpu.reg[reg2];
+			break;
 		case OR:
 			reg1 = cpu.memory[cpu.pc++];
 			reg2 = cpu.memory[cpu.pc++];
@@ -97,7 +108,6 @@ void cpu_exec(uint8_t opcode)
 			cpu.pc = addr;
 			break;
 		case JEQ:
-			reg1 = cpu.memory[cpu.pc++];
 			addr = cpu.memory[cpu.pc++];
 			if (cpu.equal_flag) {
 				cpu.pc = addr;
@@ -122,6 +132,7 @@ void cpu_exec(uint8_t opcode)
 			cpu.halted = true;
 			break;
 	}
+	cpu.increment++;
 }
 
 /*
@@ -175,6 +186,17 @@ void cpu_run()
 	{
 		uint8_t opcode = cpu.memory[cpu.pc++];
 		cpu_exec(opcode);
+		if (cpu.pc >= MEM_SIZE)
+		{
+			printf("\nProgram ended - program counter reached max memsize\n");
+			break;
+		}
+
+		if (cpu.increment > INF_LOOP_THRESHOLD)
+		{
+			printf("\nProgram ended - reached infinite loop threshold\n");
+			break;
+		}
 	}
 	printf("\n[END CPU OUTPUT]\n");
 }
@@ -187,9 +209,9 @@ void cpu_dump()
 {
 	printf("\n*** CPU state dump ***\nPC: 0x%x\nEqual flag: %d\nHalted: %d\n\n", cpu.pc, cpu.equal_flag, cpu.halted);
 
-	for (size_t i=0; i<NUM_REGISTERS; i++)
+	for (size_t i=0; i<NUM_REGISTERS; i+=2)
 	{
-		printf("R%lu: 0x%x\n", i, cpu.reg[i]);
+		printf("R%lu: 0x%04x  R%lu: 0x%04x\n", i, cpu.reg[i], i+1, cpu.reg[i+1]);
 	}
 	puts("");
 }
@@ -200,12 +222,12 @@ void cpu_dump()
 
 void mem_dump()
 {
-	printf("\n*** Memory dump ***\n");
+	printf("\n*** Memory dump ***");
 	for (size_t i=0; i<MEM_SIZE; i++)
 	{
 		if (i%20 == 0)
 		{
-			puts("");
+			printf("\n%04ld: ", i);
 		}
 
 		switch (cpu.memory[i])
@@ -218,6 +240,8 @@ void mem_dump()
 		
 			case 0xb0:
 			case 0xb1:
+			case 0xb2:
+			case 0xb3:
 				printf("\e[43m%02x\e[0m ", cpu.memory[i]);
 				break;
 
@@ -242,10 +266,14 @@ void mem_dump()
 				break;
 
 			// General purpose registers (colored foreground)
+			//case 0x00:
 			case 0x01:
 			case 0x02:
 			case 0x03:
 			case 0x04:
+			case 0x05:
+			case 0x06:
+			case 0x07:
 				printf("\e[36m%02x\e[0m ", cpu.memory[i]);
 				break;
 			default:

cpu.h

@@ -2,8 +2,9 @@
 #define CPU_H
 
 #define MEM_SIZE	256
-#define NUM_REGISTERS	4
+#define NUM_REGISTERS	8
 #define BUF_MAX     256
+#define INF_LOOP_THRESHOLD 10000
 
 /*
  * Instruction set
@@ -13,9 +14,6 @@
 
 typedef enum
 {
-	// 0x00 -> No operation
-	NOP 	= 0,
-
 	// 0xA? -> Memory operations
 	MOV 	= 0xA0,
 	PUT	= 0xA1,
@@ -23,6 +21,8 @@ typedef enum
 	// 0xB? -> Arithmetic operations
 	ADD 	= 0xB0,
 	SUB 	= 0xB1,
+	MUL	= 0xB2,
+	DIV	= 0xB3,
 
 	// 0xC? -> Bitwise operations
 	OR	= 0xC0,
@@ -39,12 +39,13 @@ typedef enum
 	CMP 	= 0xE2,
 	
 	// 0xF? -> Misc operations
+	NOP	= 0xFE,
 	HLT 	= 0xFF
 } instruction_set_t;
 
 /*
  * CPU structure definition
- * Contains 4 8-bit registers, memory, a program counter, a halt switch, and flags.
+ * Contains 8-bit registers, memory, a program counter, a halt switch, and flags.
 */
 
 typedef struct
@@ -55,6 +56,7 @@ typedef struct
 	bool halted;
 	bool equal_flag;
 	int flag_clear_delay;
+	int increment;
 } CPU_t;
 
 #endif

examples/hello.asm

@@ -0,0 +1,48 @@
+; Hello, world!
+
+PUT R1, 72
+PUT R2, 101
+PUT R3, 108
+
+OUT R1
+OUT R2
+OUT R3
+OUT R3
+
+XOR R1, R1
+XOR R2, R2
+XOR R3, R3
+
+PUT R1, 111
+PUT R2, 44
+PUT R3, 32
+
+OUT R1
+OUT R2
+OUT R3
+
+XOR R1, R1
+XOR R2, R2
+XOR R3, R3
+
+PUT R1, 119
+PUT R2, 111
+PUT R3, 114
+
+OUT R1
+OUT R2
+OUT R3
+
+XOR R1, R1
+XOR R2, R2
+XOR R3, R3
+
+PUT R1, 108
+PUT R2, 100
+PUT R3, 33
+
+OUT R1
+OUT R2
+OUT R3
+
+HLT

examples/looptext.asm

@@ -0,0 +1,10 @@
+; Loop a "Hi!"
+
+PUT R1, 104
+PUT R2, 105
+PUT R3, 32
+OUT R1
+OUT R2
+OUT R3
+JMP 0
+HLT

makefile

@@ -7,5 +7,9 @@ all: asm
 asm:
 	$(CC) assembler/*.c $(CFLAGS) -o das
 
+run:
+	./das program.asm
+	./dumb8 program.bin
+
 clean:
 	rm dumb8 das 

program.asm

@@ -1,7 +1,10 @@
 ;this is a comment
-PUT R2, 5
-MOV R1, R2
-
-ADD R1, R2
 
+PUT R0, 2
+PUT R1, 2
+CMP R0, R1
+JEQ 12
+HLT
+
+PUT R7, 10
 HLT