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 +1,174 @@
 #include "cpu.h"
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/time.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 MDR)
+{
+  cpu->ram[MAR] = MDR;
+}
+
+// ================== 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);
+}
+
+// ST function: Store value in registerB in the address stored in registerA
+// This opcode writes to memory
+void handle_ST(struct cpu *cpu)
+{
+  unsigned char MAR = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 1))];
+  unsigned char MDR = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 2))];
+  cpu_ram_write(cpu, MAR, MDR);
+}
+
+//  JMP function: Jump to the address stored in the given register
+void handle_JMP(struct cpu *cpu)
+{
+  unsigned char MAR = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 1))];
+  cpu->pc = MAR;
+}
+
+void handle_PRA(struct cpu *cpu)
+{
+  unsigned char regA = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 1))];
+  printf("%c\n", regA);
+}
+
+// ================= Handle functions ==================
+void handle_interupt(struct cpu *cpu, int location)
+{
+  cpu->registers[6] = 0;
+
+  cpu_ram_write(cpu, --cpu->registers[7], cpu->pc);
+  cpu_ram_write(cpu, --cpu->registers[7], cpu->fl);
+  for (int i = 0; i < 7; i++)
+  {
+    cpu_ram_write(cpu, --cpu->registers[7], cpu->registers[i]);
+  }
+  cpu->pc = cpu->ram[0xF8 + location];
+  cpu->registers[5] = 0;
+}
+
+void handle_IRET(struct cpu *cpu)
+{
+  for (int i = 6; i >= 0; i--)
+  {
+    cpu->registers[i] = cpu_ram_read(cpu, cpu->registers[7]++);
+  }
+  cpu->fl = cpu_ram_read(cpu, cpu->registers[7]++);
+  cpu->pc = cpu_ram_read(cpu, cpu->registers[7]++);
+  cpu->registers[5] = 1;
+}
+
+// ================= SubRoutine functions ==================
+void handle_CALL(struct cpu *cpu)
+{
+  // Saves next PC at the correct spot
+  cpu_ram_write(cpu, --cpu->registers[7], (cpu->pc + 2));
+
+  char unsigned regAVal = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 1))];
+  cpu->pc = regAVal;
+}
+
+void handle_RET(struct cpu *cpu)
+{
+  char unsigned newPc = cpu_ram_read(cpu, cpu->registers[7]++);
+  cpu->pc = newPc;
+}
+
+// ================= Stack functions ==================
+
+void handle_PUSH(struct cpu *cpu)
+{
+  char unsigned MDR = cpu->registers[cpu_ram_read(cpu, (cpu->pc + 1))];
+  cpu_ram_write(cpu, --cpu->registers[7], MDR);
+}
+
+void handle_POP(struct cpu *cpu)
+{
+  char unsigned regA = cpu_ram_read(cpu, (cpu->pc + 1));
+  unsigned char value = cpu_ram_read(cpu, cpu->registers[7]++);
+  cpu->registers[regA] = value;
+}
+
+// ================== CPU functions ===================
 
 /**
  * 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 *argv)
+{
+  FILE *ptr = fopen(argv, "r");
+  char c[100];
+  unsigned char ret;
 
   int address = 0;
-
-  for (int i = 0; i < DATA_LEN; i++) {
-    cpu->ram[address++] = data[i];
+  while (fgets(c, 100, ptr) != NULL)
+  {
+    char *endptr;
+    ret = strtoul(c, &endptr, 2);
+    if (endptr == c)
+    {
+      continue;
+    }
+    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:
+    cpu->registers[regA] = cpu->registers[regA] * cpu->registers[regB];
+    break;
+  case ALU_ADD:
+    cpu->registers[regA] = cpu->registers[regA] + cpu->registers[regB];
+    break;
+  case ALU_INC:
+    cpu->registers[regA]++;
+    break;
 
     // TODO: implement more ALU ops
   }
@@ -45,16 +179,104 @@ 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
+  time_t timePast = 0;
 
-  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.
+    struct timeval tv;
+    time_t second;
+
+    gettimeofday(&tv, NULL);
+    second = tv.tv_sec;
+    if (second != timePast)
+    {
+      cpu->registers[6] = 0b00000001;
+      timePast = second;
+    }
+
+    unsigned char interrupts = cpu->registers[5] & cpu->registers[6];
+    if (interrupts)
+    {
+      for (int i = 0; i < 8; i++)
+      {
+        int interrupt_happened = ((interrupts >> i) & 1) == 1;
+        if (interrupt_happened)
+        {
+          handle_interupt(cpu, i);
+          break;
+        }
+      }
+    }
+
+    unsigned char IR = cpu_ram_read(cpu, (cpu->pc));
+
+    // printf("ALU find IR: %d\n", (IR));
+    unsigned char ALUNUM = (0b00100000 & IR) >> 5;
+
+    if (ALUNUM == 1)
+    {
+      alu(cpu, IR);
+    }
+    else
+    {
+
+      switch (IR)
+      {
+      case LDI:
+        handle_LDI(cpu);
+        break;
+      case PRN:
+        handle_PRN(cpu);
+        break;
+      case HLT:
+        handle_HLT();
+        break;
+      case ST:
+        handle_ST(cpu);
+        break;
+      case JMP:
+        handle_JMP(cpu);
+        continue;
+      case PRA:
+        handle_PRA(cpu);
+        break;
+
+      case IRET:
+        handle_IRET(cpu);
+        continue;
+
+      // Subroutine instructions
+      case CALL:
+        handle_CALL(cpu);
+        continue;
+      case RET:
+        handle_RET(cpu);
+        continue;
+
+      //  Stack Instructions
+      case PUSH:
+        handle_PUSH(cpu);
+        break;
+      case POP:
+        handle_POP(cpu);
+        break;
+      default:
+        printf("unexpected instruction 0x%02X at 0x%02X\n", IR, cpu->pc);
+        exit(1);
+      }
+    }
+
+    int opNum = (0b11000000 & IR) >> 6;
+    cpu->pc += (opNum + 1);
   }
 }
 
@@ -64,4 +286,9 @@ void cpu_run(struct cpu *cpu)
 void cpu_init(struct cpu *cpu)
 {
   // TODO: Initialize the PC and other special registers
+  cpu->pc = 0;
+  cpu->fl = 0;
+  memset(cpu->registers, 0, sizeof(cpu->registers));
+  cpu->registers[7] = 0xF4;
+  memset(cpu->ram, 0, sizeof(cpu->ram));
 }