Kevin Sooter - Computer-Architecture

README.md

@@ -2,11 +2,12 @@
 
 ## Project
 
-* [Implement the LS-8 Emulator](ls8/)
+- [Implement the LS-8 Emulator](ls8/)
 
 ## Task List: add this to the first comment of your Pull Request
 
 ### Day 1: Get `print8.ls8` running
+
 - [ ] Inventory what is here
 - [ ] Implement `struct cpu` in `cpu.h`
 - [ ] Add RAM functions `cpu_ram_read` and `cpu_ram_write`
@@ -17,15 +18,18 @@
 - [ ] Add the `PRN` instruction
 
 ### Day 2: Add the ability to load files dynamically, get `mult.ls8` and `stack.ls8` running
+
 - [ ] Un-hardcode the machine code
 - [ ] Implement the `cpu_load` function to load an `.ls8` file given the filename passed in as an argument
 - [ ] Implement a Multiply instruction and Print the result (run `mult8.ls8`)
 - [ ] Implement the System Stack and be able to run the `stack.ls8` program
 
 ### Day 3: Get `call.ls8` running
+
 - [ ] Implement the CALL and RET instructions
 - [ ] Implement Subroutine Calls and be able to run the `call.ls8` program
 
 ### Stretch
+
 - [ ] Add the timer interrupt to the LS-8 emulator
 - [ ] Add the keyboard interrupt to the LS-8 emulator

ls8/cpu.c

@@ -1,40 +1,87 @@
 #include "cpu.h"
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
 
-#define DATA_LEN 6
+// ================== RAM functions ===================
+
+/**  Read from the CPU's ram at the specifc location 
+ */
+unsigned char cpu_ram_read(struct cpu *cpu, unsigned char MAR)
+{
+  return cpu->ram[MAR];
+}
+
+/**  Writes at index specified for the CPU's ram
+ */
+void cpu_ram_write(struct cpu *cpu, unsigned char MAR, unsigned char num)
+{
+  cpu->ram[MAR] = num;
+}
+
+// ================== Instrcution Handlers ===================
+
+// LDI function: Set the value of a register to an integer
+void handle_LDI(struct cpu *cpu)
+{
+  unsigned char regA = cpu_ram_read(cpu, (cpu->pc + 1));
+  unsigned char value = cpu_ram_read(cpu, (cpu->pc + 2));
+  cpu->registers[regA] = value;
+};
+
+// PRN function: Print numeric value stored in the given register
+void handle_PRN(struct cpu *cpu)
+{
+  unsigned char regA = cpu_ram_read(cpu, (cpu->pc + 1));
+  printf("%d\n", cpu->registers[regA]);
+}
+
+// HLT function: Halt the CPU (and exit the emulator)
+void handle_HLT()
+{
+  exit(0);
+}
+
+// ================== CPU functions ===================
 
 /**
  * Load the binary bytes from a .ls8 source file into a RAM array
  */
-void cpu_load(struct cpu *cpu)
+void cpu_load(struct cpu *cpu, char *argv)
 {
-  char data[DATA_LEN] = {
-    // From print8.ls8
-    0b10000010, // LDI R0,8
-    0b00000000,
-    0b00001000,
-    0b01000111, // PRN R0
-    0b00000000,
-    0b00000001  // HLT
-  };
+  FILE *ptr = fopen(argv, "r");
+  char c[100];
+  long ret;
 
   int address = 0;
-
-  for (int i = 0; i < DATA_LEN; i++) {
-    cpu->ram[address++] = data[i];
+  while (fgets(c, 100, ptr) != NULL)
+  {
+    if (c[0] == '1' || c[0] == '0')
+    {
+      ret = strtoul(c, NULL, 2);
+      cpu_ram_write(cpu, address++, ret);
+    }
   }
 
+  fclose(ptr);
+
   // TODO: Replace this with something less hard-coded
 }
 
 /**
  * ALU
  */
-void alu(struct cpu *cpu, enum alu_op op, unsigned char regA, unsigned char regB)
+void alu(struct cpu *cpu, enum alu_op op)
 {
-  switch (op) {
-    case ALU_MUL:
-      // TODO
-      break;
+  unsigned char regA = cpu_ram_read(cpu, (cpu->pc + 1));
+  unsigned char regB = cpu_ram_read(cpu, (cpu->pc + 2));
+
+  switch (op)
+  {
+  case ALU_MUL:
+    // TODO
+    cpu->registers[regA] = cpu->registers[regA] * cpu->registers[regB];
+    break;
 
     // TODO: implement more ALU ops
   }
@@ -45,16 +92,45 @@ void alu(struct cpu *cpu, enum alu_op op, unsigned char regA, unsigned char regB
  */
 void cpu_run(struct cpu *cpu)
 {
+
   int running = 1; // True until we get a HLT instruction
 
-  while (running) {
+  while (running)
+  {
     // TODO
     // 1. Get the value of the current instruction (in address PC).
     // 2. Figure out how many operands this next instruction requires
     // 3. Get the appropriate value(s) of the operands following this instruction
     // 4. switch() over it to decide on a course of action.
     // 5. Do whatever the instruction should do according to the spec.
     // 6. Move the PC to the next instruction.
+    unsigned char IR = cpu_ram_read(cpu, (cpu->pc));
+
+    switch (IR)
+    {
+    case LDI:
+      handle_LDI(cpu);
+      break;
+
+    case PRN:
+      handle_PRN(cpu);
+      break;
+
+    case HLT:
+      handle_HLT();
+      break;
+
+    case MUL:
+      alu(cpu, ALU_MUL);
+      break;
+
+    default:
+      printf("unexpected instruction 0x%02X at 0x%02X\n", IR, cpu->pc);
+      exit(1);
+    }
+
+    int opNum = (11000000 & IR) >> 6;
+    cpu->pc += (opNum + 1);
   }
 }
 
@@ -64,4 +140,8 @@ void cpu_run(struct cpu *cpu)
 void cpu_init(struct cpu *cpu)
 {
   // TODO: Initialize the PC and other special registers
+  cpu->pc = 0;
+  memset(cpu->registers, 0, sizeof(cpu->registers));
+  cpu->registers[7] = 0xF4;
+  memset(cpu->ram, 0, sizeof(cpu->ram));
 }

ls8/cpu.h

@@ -2,32 +2,39 @@
 #define _CPU_H_
 
 // Holds all information about the CPU
-struct cpu {
+struct cpu
+{
   // TODO
   // PC
+  unsigned char pc;
   // registers (array)
+  unsigned char registers[8];
   // ram (array)
+  unsigned char ram[256];
 };
 
 // ALU operations
-enum alu_op {
-	ALU_MUL
-	// Add more here
+enum alu_op
+{
+  ALU_MUL
+  // Add more here
 };
 
 // Instructions
 
 // These use binary literals. If these aren't available with your compiler, hex
 // literals should be used.
 
-#define LDI  0b10000010
-#define HLT  0b00000001
-#define PRN  0b01000111
+#define LDI 0b10000010
+#define HLT 0b00000001
+#define PRN 0b01000111
+#define MUL 0b10100010
+
 // TODO: more instructions here. These can be used in cpu_run().
 
 // Function declarations
 
-extern void cpu_load(struct cpu *cpu);
+extern void cpu_load(struct cpu *cpu, char *argv);
 extern void cpu_init(struct cpu *cpu);
 extern void cpu_run(struct cpu *cpu);
 

ls8/ls8.c

@@ -1,16 +1,30 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include "cpu.h"
 
 /**
  * Main
  */
-int main(void)
+int main(int argc, char *argv[])
 {
+  if (argc < 2)
+  {
+    fprintf(stderr, "Not enough arguments.\nUsage: ./ls8 {file path from current directory}\n");
+    exit(1);
+  }
+
+  FILE *fptr;
+  if ((fptr = fopen(argv[1], "r")) == NULL)
+  {
+    printf("No such file.\n");
+    exit(1);
+  }
+  fclose(fptr);
   struct cpu cpu;
 
   cpu_init(&cpu);
-  cpu_load(&cpu);
+  cpu_load(&cpu, argv[1]);
   cpu_run(&cpu);
 
   return 0;
-}
+}