csim

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use Term::ReadKey;
use IO::Pty;
use Storable;

# CSCVon8 Simulator, (C) 2019 Warren Toomey, GPL3

my @RAM= (0) x 32768;
my @ROM;
my $ALUROM;
my @DecodeROM;
my $debug=0;
my $PC=0;
my $A=0;
my $B=0;
my $AH=0;
my $AL=0;
my $IR=0;
my $phase=0;

my $aluop;
my $loadop;
my $dbusop;
my $jumpop;
my $arena;
my $pcincr;
my $usreset;

# The 1-char buffer from the keyboard. undefined means no character.
my $inchar;

# By default, UART I/O goes to STDIN/OUT
my $IN=   *STDIN;
my $OUT= *STDOUT;

# List of control line masks and shifts.
use constant {
  ALUOP    => 0x001f,
  LOADOP   => 0x0007, LOADSHIFT => 5,
  DBUSOP   => 0x0003, DBUSSHIFT => 8,
  JUMPOP   => 0x0007, JUMPSHIFT => 10,
  ARENA    => 0x0001, ARSHIFT => 13,		# Active low
  PCINCR   => 0x0001, PCSHIFT => 14,
  USRESET  => 0x0001, USSHIFT => 15,		# Active low
  IRSHIFT  => 4,
  CSHIFT => 8,
  VSHIFT => 9,
  ZSHIFT => 10,
  NSHIFT => 11,
  DSHIFT => 12,
  MEMRESULT => 0,
  ALURESULT => 1,
  UARTRESULT => 2,
};

# List of ALUop names
my @ALUop = (
    "0",
    "A",
    "B",
    "-A",
    "-B",
    "A+1",
    "B+1",
    "A-1",
    "B-1",
    "A+B",
    "A+B+1",
    "A-B",
    "A-Bspecial",
    "B-A",
    "A-B-1",
    "B-A-1",
    "A*BHI",
    "A*BLO",
    "A/B",
    "A%B",
    "A<<B",
    "A>>BL",
    "A>>BA",
    "AROLB",
    "ARORB",
    "A&B",
    "A|B",
    "A^B",
    "!A",
    "!B",
    "A+BCD",
    "A-BCD"
);

# Enable debugging, pty I/O and randomised memory
while (@ARGV > 0) {
  # Set debug mode
  if ($ARGV[0] eq "-d") { $debug++; shift(@ARGV); next; }

  # Open up a pty
  if ($ARGV[0] eq "-p") {
    $OUT = new IO::Pty; $IN= $OUT;
    print("pty is ", $OUT->ttyname(), "\n");
    shift(@ARGV); next;
  }

  # Randomise the RAM
  if ($ARGV[0] eq "-r") {
    foreach my $i (0 .. 32767) {
      $RAM[$i]= int(rand(256));
    }
    shift(@ARGV); next;
  }
  die("Usage: $0 [-d] [-p] [-r]\n-d: debug, -r: randomise RAM, -p: open pty\n");
}

# Set the UART up to read one char at a time
ReadMode('cbreak', $IN);

# Load the ALU ROM
my $ROMIN;
if (-f "alu.hex") {
  $ALUROM = retrieve("alu.hex");
} else {
  # Load the ROM file and store a cached version
  open( $ROMIN, "<", "alu.rom" ) || die("Can't open alu.rom: $!\n");
  while (<$ROMIN>) {
    chomp; push( @{ $ALUROM }, map( { hex($_) } split( /\s/, $_ ) ) );
  }
  close($ROMIN);
  store($ALUROM, "alu.hex");
}

# Load the Decode ROM
open( $ROMIN, "<", "ucode.rom" ) || die("Can't open ucode.rom: $!\n");
while (<$ROMIN>) {
    chomp; push( @DecodeROM, map( { hex($_) } split( /\s+/, $_ ) ) );
}
close($ROMIN);

# Load the instruction ROM
open( $ROMIN, "<", "instr.rom" ) || die("Can't open instr.rom: $!\n");
while (<$ROMIN>) {
    chomp; push( @ROM, map( { hex($_) } split( /\s+/, $_ ) ) );
}
close($ROMIN);

# Start the simulation
while (1) {
  # Work out the decode ROM index
  my $decodeidx= ($IR << IRSHIFT) | $phase;

  # Get the microinstruction
  my $uinst= $DecodeROM[ $decodeidx ];

  # Decode the microinstruction
  $aluop= $uinst & ALUOP;
  $loadop= ($uinst>>LOADSHIFT) & LOADOP;
  $dbusop= ($uinst>>DBUSSHIFT) & DBUSOP;
  $jumpop= ($uinst>>JUMPSHIFT) & JUMPOP;
  $arena=  ($uinst>>ARSHIFT)   & ARENA;
  $pcincr= ($uinst>>PCSHIFT)   & PCINCR;
  $usreset= ($uinst>>USSHIFT)  & USRESET;
  printf("PC %04x IR %02x p %01x ui %04x upa %d%d%d ", $PC,
		$IR, $phase, $uinst, $usreset, $pcincr, $arena) if ($debug);

  # Do the ALU operation.
  my $databus=0;
  my ($carry, $overflow, $zero, $negative, $divbyzero);
  if ($dbusop== ALURESULT) {
    my $aluresult= $ALUROM->[ ($aluop<<16) | ($A<<8) | $B ];
    printf("AB %02x %02x %s %04x ", $A, $B, $ALUop[$aluop], $aluresult)
								if ($debug);

    # Extract the flags from the result, and remove from the result
    $carry= ($aluresult>>CSHIFT) & 1;
    $overflow= ($aluresult>>VSHIFT) & 1;
    $zero= ($aluresult>>ZSHIFT) & 1;
    $negative= ($aluresult>>NSHIFT) & 1;
    $divbyzero= ($aluresult>>DSHIFT) & 1;
    $databus = $aluresult & 0xff;
  }

  # Determine the address on the address bus: AR or PC
  my $address;
  if ($arena==0) {
    $address= ($AH<<8) | $AL;
    printf("AR %02x%02x ", $AH, $AL) if ($debug);
  } else {
    $address= $PC;
    printf("PC %04x ", $PC) if ($debug);
  }

  # Get the memory value
  if ($dbusop== MEMRESULT) {
    $databus= ($address & 0x8000) ? $RAM[$address-0x8000] : $ROM[$address];
  }

  # Read from UART. Wait up to 0.5 seconds,
  # and if no character, "read" a NUL character.
  if ($dbusop== UARTRESULT) {
    # Return 0 if they were silly enough to read when nothing is there.
    # Empty the buffer regardless.
    $databus = defined($inchar) ? ord($inchar) : 0;

    # Only reset $inchar if there is a reader on the data bus. This
    # allows UARTRESULT to be asserted for several microinstructions
    # before the actual read is done.
    $inchar= undef if ($loadop);
  }
  printf("dop %x dbus %02x ", $dbusop, $databus) if ($debug);

  # Load from the data bus
  if ($loadop==1) { $IR= $databus; print("->IR ") if ($debug); }
  if ($loadop==2) { $A= $databus; print("->A ") if ($debug); }
  if ($loadop==3) { $B= $databus; print("->B ") if ($debug); }
  if ($loadop==4) {
    if ($address & 0x8000) { $RAM[$address-0x8000]= $databus; }
    print("->RAM ") if ($debug);
  }
  if ($loadop==5) { $AH= $databus; print("->AH ") if ($debug); }
  if ($loadop==6) { $AL= $databus; print("->AL ") if ($debug); }
  if ($loadop==7) {
    print($OUT chr($databus)); $|=1;		# Flush the output
    print("->IO ") if ($debug);
  }

  # Increment the PC and the phase
  $PC++ if ($pcincr==1);
  $phase= ($usreset==0) ? 0 : ($phase+1) & 0xf;

  # Do any jumps
  printf("j%d ", $jumpop) if ($jumpop && $debug);
  if ($jumpop==1 && $carry) {
    $PC= $address;
    print("JC ") if ($debug);
  }
  if ($jumpop==2 && $overflow) {
    $PC= $address;
    print("JO ") if ($debug);
  }
  if ($jumpop==3 && $zero) {
    $PC= $address;
    print("JZ ") if ($debug);
  }
  if ($jumpop==4 && $negative) {
    $PC= $address;
    print("JN ") if ($debug);
  }
  if ($jumpop==5 && $divbyzero) {
    $PC= $address;
    print("JD ") if ($debug);
  }

  # If the instruction is testing for an available UART character to
  # read and we have one, don't jump. If not, try to read one and
  # jump if that fails. If we read one, put it in the $inchar buffer.
  if ($jumpop==7 && !defined($inchar)) {

    # This code if we are reading from a terminal
    if (-t $IN) {
      $inchar= ReadKey(0.5, $IN);
    } else {
      # This code for files and pipes
      $inchar= getc($IN);
      printf("File/pipe read %02x ", (defined($inchar) ? ord($inchar) : 0xff)) if ($debug);
    }

    # There was no character to read
    if (!defined($inchar)) {
      $PC= $address; print("JI ") if ($debug);
    }
  }

  # Exit if PC goes to $FFFF
  last if ($PC==0xffff);
  print("\n") if ($debug);
}

# Clean up and exit
ReadMode('normal', $IN);
exit(0);