From 6e582412883b045ba9a66705a69e3f80ec53eef6 Mon Sep 17 00:00:00 2001
From: n loewen <nick@nloewen.com>
Date: Mon, 3 Mar 2025 19:52:12 +0000
Subject: [PATCH] Implement remaining instructions + basic 5x5 display printout

---
 src/cpu.py | 185 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)
 create mode 100644 src/cpu.py

diff --git a/src/cpu.py b/src/cpu.py
new file mode 100644
index 0000000..7da5078
--- /dev/null
+++ b/src/cpu.py
@@ -0,0 +1,185 @@
+import sys
+
+class CPU:
+    def __init__(self):
+        self.running = False
+        self.IP = 254
+        self.acc = 0
+        self.flags = { 'C': False, 'Z': False, 'N': False, 'Eq': False }
+        self.instruction = { 'opcode': False, 'operand': False }
+        self.memory = False
+
+    def load_memory(self, bytes):
+        self.memory = bytes + bytearray(256 - len(bytes))
+        print('mem 254', self.memory[254])
+        # print(self.memory)
+
+    def start(self):
+        self.running = True
+
+    def print_screen(self):
+        for i in range(5):
+            for j in range(5):
+                # print(f"{i}-{j}", end=" ")
+                # print(self.memory[(i*5)+j], end=" ")
+                memory_index = (i * 5) + j
+                if self.memory[memory_index] > 0:
+                    print("#", end="  ")
+                else:
+                    print("_", end="  ")
+            print()
+
+    def step(self):
+        if self.IP >= 256:
+            self.IP = 0
+        print("IP:", self.IP)
+        self.instruction['opcode'] = self.memory[self.IP]
+        self.IP = self.IP+1
+        self.instruction['operand'] = self.memory[self.IP]
+        self.IP = self.IP+1
+        print("instr:", self.instruction['opcode'], self.instruction['operand'])
+        print("mnem:", self.nums2mnems[self.instruction['opcode']])
+        self.nums2mnems[self.instruction['opcode']](self, self.instruction['operand'])
+        print("acc:", self.acc)
+        print("running:", self.running)
+        print()
+        self.print_screen()
+        print()
+        if not self.running:
+            sys.exit()
+
+    def hlt(self, operand):
+        self.running = False
+
+    def nop(self, operand):
+        pass
+
+    def lda_lit(self, operand):
+        self.acc = operand
+
+    def lda_mem(self, operand):
+        self.acc = memory[operand]
+
+    def sta_lit(self, operand):
+        memory[operand] = self.acc
+
+    def sta_mem(self, operand):
+        memory[memory[operand]] = self.acc
+
+    def add_lit(self, operand):
+        self.acc = self.acc + operand
+        if self.acc > 255:
+            self.acc = self.acc % 256
+            self.flags['C'] = True
+        else:
+            self.flags['C'] = False
+        self.flags['Z'] = True if self.acc == 0 else False
+        self.flags['Eq'] = True if self.acc == operand else False
+        self.flags['N'] = True if self.acc > 127 else False
+
+    def add_mem(self, operand):
+        self.acc = self.acc + self.memory[operand]
+        if self.acc > 255:
+            self.acc = self.acc % 256
+            self.flags['C'] = True
+        else:
+            self.flags['C'] = False
+        self.flags['Z'] = True if self.acc == 0 else False
+        self.flags['Eq'] = True if self.acc == operand else False
+        self.flags['N'] = True if self.acc > 127 else False
+
+    def sub_lit(self, operand):
+        self.acc = self.acc - operand
+        if self.acc < 0:
+            self.acc = self.acc % 256
+            self.flags['C'] = True
+        else:
+            self.flags['C'] = False
+        self.flags['Z'] = True if self.acc == 0 else False
+        self.flags['Eq'] = True if self.acc == operand else False
+        self.flags['N'] = True if self.acc > 127 else False
+
+    def sub_mem(self, operand):
+        self.acc = self.acc - self.memory[operand]
+        if self.acc > 255:
+            self.acc = self.acc % 256
+            self.flags['C'] = True
+        else:
+            self.flags['C'] = False
+        self.flags['Z'] = True if self.acc == 0 else False
+        self.flags['Eq'] = True if self.acc == operand else False
+        self.flags['N'] = True if self.acc > 127 else False
+
+    def jmp_lit(self, operand):
+        self.IP = operand
+
+    def jmp_mem(self, operand):
+        self.IP = memory[operand]
+
+    def ske(self, operand):
+        if self.flags['Eq']:
+            self.IP += 2
+
+    def skz(self, operand):
+        if self.flags['Z']:
+            self.IP += 2
+
+    def skn(self, operand):
+        if self.flags['N']:
+            self.IP += 2
+
+    def skc(self, operand):
+        if self.flags['C']:
+            self.IP += 2
+
+    def cst(self, operand):
+        self.flags['C'] = True
+
+    def ccl(self, operand):
+        self.flags['C'] = False
+
+    nums2mnems = {
+        0: hlt,
+        1: nop,
+        2: lda_lit,
+        3: sta_lit,
+        4: add_lit,
+        5: sub_lit,
+        6: jmp_lit,
+        7: ske,
+        8: skz,
+        9: skn,
+        10: skc,
+        11: cst,
+        12: ccl,
+        16: hlt,
+        17: nop,
+        18: lda_mem,
+        19: sta_mem,
+        20: add_mem,
+        21: sub_mem,
+        22: jmp_mem,
+        23: ske,
+        24: skz,
+        25: skn,
+        26: skc,
+        27: cst,
+        28: ccl,
+    }
+
+cpu = CPU()
+
+prog = '04 FF 04 01 14 01 00 00'
+program_bytes = bytes.fromhex(prog)
+# Add jmp at addr 254:
+program_with_jump = program_bytes + bytearray(254 - len(program_bytes)) + bytes.fromhex('06 00')
+cpu.load_memory(program_with_jump)
+
+cpu.print_screen()
+
+cpu.start()
+cpu.step()
+cpu.step()
+cpu.step()
+cpu.step()
+cpu.step()