in reply to Parsing through instructions

We could help you better if you gave us a small sample of your actual input data and the output you expect. As it is I have no idea what you are really asking for help with. Are you having trouble decoding a bunch of bits to determine what the instruction is? Are you having trouble simulating some form of processor? Are you having trouble opening a file and reading its contents? I simply have NO idea what your problem is.

True laziness is hard work

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Re^2: Parsing through instructions
by DaveMonk (Acolyte) on Apr 08, 2012 at 21:53 UTC
    Ok so this is part of what I have: 
     byte 1               byte 2 (optional)
 bits      [ 7 6 5 4 3 2 1 0 ]  [ 7 6 5 4 3 2 1 0 ]
 opcode      - - -             
 mod               -           
 operand1            - - - -
 operand2                         - - - - - - - -

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    And instructions: 
     opcode | instruction | operands (mod 0) | operands (mod 1)
 -------+-------------+------------------+-----------------
 0x00   | jmp         | r1               | r2:r1
 0x01   | movr        | r1, r2           | rx,   imm 
 0x02   | movm        | r1, [ds:r2]      | [ds:r1], r2
 0x03   | add         | r1, r2           | r1,   imm

 flags
 
 cmp r1, r2 instruction results in:
    r1 == r2 => fl = 0
    r1 < r2  => fl = 0xff
    r1 > r2  => fl = 1
 
    jmpe r1
    => if (fl == 0) jmp r1
    else nop

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    I am then given: 
     0x00 0x00 0x00 0x01 0x03 0x02 0x03 0x02 0x03 0x02

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    But pretty much like you said, I am in need of simulating a processor with given instructions.
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[d/l]
[select]

      So the key information you need is that you need to use the bit operators to manipulate the bits in each byte to extract the interesting bit fields. In particular use & (bitwise and) and a bit mask to isolate bit fields, and use the bitwise shift operators >> and << to move fields of bits about. For example, to isolate the op code you'd do something like:

      use strict;
use warnings;

my $byte = 0b00100100;
my $opCode = ($byte & 0b11100000) >> 5;

printf "Opcode is 0x%02X\n", $opCode;

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      Prints:

      Opcode is 0x01

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      See perlop for details about the various Perl operators.

      True laziness is hard work
[reply]
[d/l]
[select]
        Awesome man, but I still need some help figuring out how to do this for the other 8 instructions, and then run it (the asm code) and dump to a file. But I have been playing around with perlop :)
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