asm/logicCpu.py

   1 #!env python
   2 # Created:20080415
   3 # By Antonio Chavez
   4 #
   5 # 3-trit Computer Simulator
   6 # usage: logicCpu program.3
   7 # This program simulates the hardware of the 3 trit computer we are
   8 #    developing. Input to the program is a ".3" file which should contain
   9 #    three encoded instructions to simulate on the first line.  Once started,
  10 #    the user may interactively change the "IN" register at any time.
  11 #    Execution begins with instruction at program counter 0.
  12
  13 import sys, os, threading, time
  14
  15 TRACE = True
  16 DELAY = 1                   # second(s)
  17 USER_INPUT_THREAD = True    # ask for user input?
  18 USER_INPUT_INIT = 8         # initialize input to this
  19
  20 trit_integer = {"i": -1, "0":0, "1":1}
  21
  22 # Lookup a register's name by address
  23 register_name = {
  24         -1: "IN",
  25          0: "OUT",
  26          1: "A"
  27     }
  28
  29 # Register contents
  30 registers = {
  31         "IN":  0,
  32         "OUT": 0,
  33         "A":   0,
  34         "S":   1
  35     }
  36
  37 # Thread that gets input from user
  38 class CPUInput (threading.Thread):
  39     def run (self):
  40         while True:
  41             print "Register Status: %s :" % registers,
  42             user_input = raw_input('Input value for IN:')
  43
  44             try:
  45                 digit = int(user_input)
  46             except ValueError, e:
  47                 print "invalid input: %s (%s)" % (user_input, e)
  48                 continue
  49
  50             if digit >= -4 and digit <= 4:
  51                 registers["IN"] = digit
  52             else:
  53                 print """invalid input: %s""" % user_input
  54
  55 def main():
  56     # check arguments
  57     if len(sys.argv) < 2 or len(sys.argv) > 2:
  58         print """usage: %s program.3
  59 input file: program.3 - machine code
  60 """ % (sys.argv[0])
  61         raise SystemExit
  62
  63     if (sys.argv[1])[len(sys.argv[1])-1:] != "3":
  64          print """\'%s\' is an invalid filetype""" % sys.argv[1]
  65          raise SystemExit
  66
  67     # retrieve file
  68     codefile = file(sys.argv[1], "rt")
  69     tritstream = codefile.readline()
  70
  71     # check for errors in file
  72     if codefile == []:
  73         print """\'%s\' files is empty""" % (sys.argv[1])
  74         raise SystemExit
  75
  76     for i in tritstream:
  77         if not i in trit_integer:
  78             print """invalid char \'%s\' in file \'%s\'""" % (i, sys.argv[1])
  79             raise SystemExit
  80
  81     if len(tritstream) != 9:
  82         print """3 instructions must be provided in \'%s\'""" % (sys.argv[1])
  83         raise SystemExit
  84
  85     # memory, registers, and program counter
  86     memory = {}
  87     registers["PC"] = 0
  88
  89     # decode instructions from file
  90     for i in range(-1, 2):
  91         print "%2d: " % (i),
  92         memory[i] = Decoder(tritstream)
  93         tritstream = tritstream[3:]
  94
  95     # start user input thread
  96     if USER_INPUT_THREAD:
  97         CPUInput().start()
  98     registers["IN"] = USER_INPUT_INIT
  99
 100     # execute instructions
 101     while True:
 102         registers["PC"] = Execute(memory)
 103
 104         if TRACE:
 105             print registers
 106
 107         time.sleep(DELAY)
 108
 109 def Decoder(tritstream):
 110     """ Decode a single instruction.
 111         tristream: stream of trits will only process the first 3 trits.
 112         return: dictionary containing the operation
 113     """
 114     inst = {"op":trit_integer[tritstream[0]]}
 115
 116     # cmp and be
 117     if inst["op"] == -1 or inst["op"] == 1:
 118
 119         if inst["op"] == -1:
 120             print "cmp ",
 121         else:
 122             print "be  ",
 123
 124         inst["src1"] = trit_integer[tritstream[1]]
 125         print "%2d," % inst["src1"],
 126         inst["src2"] = trit_integer[tritstream[2]]
 127         print "%2d" % inst["src2"]
 128
 129     # lwi
 130     elif inst["op"] == 0:
 131         print "lwi ",
 132         inst["src1"] = trit_integer[tritstream[1]]
 133         inst["src2"] = trit_integer[tritstream[2]]
 134         inst["immed"] = 3*inst["src1"] + inst["src2"]
 135         print "%2d" % inst["immed"]
 136
 137     return inst
 138
 139 def Execute(memory):
 140     """ Execute one instruction.
 141         memory: were decoded instructions are stored
 142         registers: contains registers and their values
 143         returns: new program counter, to be stored in registers["PC"]
 144     """
 145
 146     op = (memory[registers["PC"]])["op"]
 147
 148     # cmp
 149     if op == -1:
 150         src1 = (memory[registers["PC"]])["src1"]
 151         src2 = (memory[registers["PC"]])["src2"]
 152         if registers[register_name[src1]] < registers[register_name[src2]]:
 153             registers["S"] = -1
 154         elif registers[register_name[src1]] > registers[register_name[src2]]:
 155             registers["S"] = 1
 156         else:
 157             registers["S"] = 0
 158         new_pc = registers["PC"] + 1
 159     # lwi
 160     elif op == 0:
 161         registers["A"] = (memory[registers["PC"]])["immed"]
 162         new_pc = registers["PC"] + 1
 163     # be
 164     elif op == 1:
 165         if registers["S"] == 0:
 166             new_pc = (memory[registers["PC"]])["src1"]
 167         else:
 168             new_pc = (memory[registers["PC"]])["src2"]
 169
 170     if new_pc > 1:
 171        new_pc = -1
 172
 173     return new_pc
 174
 175 if __name__ == "__main__":
 176     main()