Computer-Architecture - Pedro Montesinos

ls8/cpu.c

@@ -1,29 +1,38 @@
+#include "stdio.h"
+#include "stdlib.h"
+#include "string.h"
 #include "cpu.h"
 
 #define DATA_LEN 6
 
+unsigned cpu_ram_read(struct cpu *cpu, unsigned char address){
+  return cpu->ram[address];
+}
+
+void cpu_ram_write(struct cpu *cpu, unsigned char address, unsigned char val){
+  cpu->ram[address] = val;
+};
+
 /**
  * Load the binary bytes from a .ls8 source file into a RAM array
  */
-void cpu_load(struct cpu *cpu)
-{
-  char data[DATA_LEN] = {
-    // From print8.ls8
-    0b10000010, // LDI R0,8
-    0b00000000,
-    0b00001000,
-    0b01000111, // PRN R0
-    0b00000000,
-    0b00000001  // HLT
-  };
 
+void cpu_load(struct cpu *cpu, char *path)
+{
+  FILE *filepointer = fopen(path, "r");
+  if(filepointer == NULL){
+    printf("Couldn't open the program you entered: %s\n", path);
+    exit(2);
+  }
   int address = 0;
-
-  for (int i = 0; i < DATA_LEN; i++) {
-    cpu->ram[address++] = data[i];
+  char line[8000];
+  while(fgets(line, sizeof(line), filepointer) != NULL){
+    char *endpointer;
+    if(endpointer == line){
+      continue;
+    }
+
   }
-
-  // TODO: Replace this with something less hard-coded
 }
 
 /**
@@ -50,11 +59,32 @@ void cpu_run(struct cpu *cpu)
   while (running) {
     // TODO
     // 1. Get the value of the current instruction (in address PC).
+    unsigned char instruction = cpu_ram_read(cpu, cpu->PC);
     // 2. Figure out how many operands this next instruction requires
+      // Not needed if we use a switch statement
     // 3. Get the appropriate value(s) of the operands following this instruction
+    unsigned char op0 = cpu_ram_read(cpu, cpu->PC + 1);
+    unsigned char op1 = cpu_ram_read(cpu, cpu->PC + 2);
+    printf("trace: %02X: %02X    %02X   %02X\n", cpu->PC, instruction, op0, op1);
     // 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.
+    switch (instruction){
+      case LDI:
+        cpu->regs[op0] = op1;
+        cpu->PC += 3;
+        break;
+      case PRN:
+        printf("%d\n", cpu->regs[op0]);
+        cpu->PC += 2;
+        break;
+      case HLT: //HLT the cpu and exit the emulator
+        running = 0;
+        break;
+      default:
+        printf("unexpected instruction 0x%02X at 0x%02X\n", instruction, cpu->PC);
+        exit(1);
+    }
   }
 }
 
@@ -64,4 +94,12 @@ void cpu_run(struct cpu *cpu)
 void cpu_init(struct cpu *cpu)
 {
   // TODO: Initialize the PC and other special registers
+  for(int i = 0; i < 7; i++){
+    cpu->regs[i] = 0;
+  }
+  cpu->regs[7] = 0xF4;
+
+  cpu->PC = 0;
+  cpu->FL = 0;
+  memset(cpu->ram, 0, sizeof cpu->ram);
 }

ls8/cpu.h

@@ -5,8 +5,13 @@
 struct cpu {
   // TODO
   // PC
+  unsigned char PC;
   // registers (array)
+  unsigned char regs[8];
   // ram (array)
+  unsigned char ram[256];
+  //flag
+  unsigned char FL;
 };
 
 // ALU operations

ls8/ls8.c

@@ -13,4 +13,4 @@ int main(void)
   cpu_run(&cpu);
 
   return 0;
-}
+}