almost there, for an initial impl.

ironically test.py ended up way more advanced than dcpu_16.py

dcpu_16.py

@@ -0,0 +1,136 @@
+# System width
+w = 16
+wmask = 2**16-1
+
+# Literal values
+literal = xrange(0x00, 0x20)
+
+opcodes = [
+    'nbi',
+    'SET',
+    'ADD',
+    'SUB',
+    'MUL',
+    'DIV',
+    'MOD',
+    'SHL',
+    'SHR',
+    'AND',
+    'BOR',
+    'XOR',
+    'IFE',
+    'IFN',
+    'IFG',
+    'IFB',
+]
+
+class CPU(object):
+
+    class Ops(object):
+        def SET(c, a, b):
+            return None
+        def ADD(c, a, b):
+            return None
+        def SUB(c, a, b):
+            return None
+        def MUL(c, a, b):
+            return None
+        def DIV(c, a, b):
+            return None
+        def MOD(c, a, b):
+            return None
+        def SHL(c, a, b):
+            return (a << b) & wmask
+        def SHR(c, a, b):
+            return (a >> b)
+        def AND(c, a, b):
+            return a & b
+        def BOR(c, a, b):
+            return a | b
+        def XOR(c, a, b):
+            return a ^ b
+        def IFE(c, a, b):
+            return a == b
+        def IFN(c, a, b):
+            return a != b
+        def IFG(c, a, b):
+            return a > b
+        def IFB(c, a, b):
+            return (a & b) != 0
+
+    def __init__(c):
+        c.reset()
+        c.clear()
+
+    def reset(c):
+        """Reset CPU"""
+        c.r = [0 for _ in xrange(0, w)]
+        c.pc = 0
+        c.sp = 0
+        c.o  = False
+        c.skip = False
+
+    def clear(c):
+        """Clear memory"""
+        c.m = [0 for _ in xrange(0, 2**w)]
+
+    def __getitem__(c, addr):
+        """Read value at memory address"""
+        return c.m[addr]
+
+    def __setitem__(c, addr, value):
+        """Write value at memory address"""
+        c.m[addr] = value
+
+    def next_word(c):
+        val = c[c.pc]
+        c.pc += 1
+        return val
+
+    def dispatch_op(c):
+
+        def get_opcode(word):
+            return word & 0xF
+        def get_a(word):
+            return (word >>  4) & 0x3F
+        def get_b(word):
+            return (word >> 10) & 0x3F
+
+        def get_op(word):
+            getattr(CPU.Ops, opcodes[get_opcode(word)])
+
+        def is_nbi(opcode):
+            return opcode == 0x0
+        def is_set(opcode):
+            return 0x0 < opcode <= 0xb
+        def is_skip(opcode):
+            return 0xb < opcode <= 0xf
+        def set_a(value):
+            pass
+
+        word = c.next_word()
+        if c.skip:
+            c.skip = False
+            return
+
+        opcode = get_opcode(word)
+        if is_nbi(opcode):
+            pass
+        elif is_set(opcode):
+            set_a(get_op(opcode)())
+        elif is_skip(opcode):
+            if not get_op(opcode)():
+                c.skip = True
+        else:
+            raise OpcodeError(c.pc, opcode)
+
+
+
+class OpcodeError(Exception):
+    def __init__(self, addr, data):
+        self.addr = addr
+        self.data = data
+
+    def __str__(self):
+        return "Invalid opcode at %s: '%s'" % (self.addr, self.data)
+