dasm - Z8001 disassembler

   Copyright Matt Knoth 2008 (p8000@earthlink.net)

   based on Juergen Buchmueller's Z8002 MAME model

   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

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   Compile:     gcc -Wall dasm.c

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   USAGE:

   dasm [-s] [-a] [-t 1/2] [-p <start_pc>] [-o <file_offset>] [-n <n_bytes>] <Z8001_binary>
               number prefix '0x'-hex, '0'-octal, else decimal
           -s  segmented mode, non-segmented default
           -a  display pc and segment number as 32bit hex, rather than <<%seg>>%base
           -t  test mode: -t1 hex encoding, 1 instruction/line, -t2 hex encoding consecutively - newlines accepted
           -p  preset PC to argument value
           -n  stop disassemble after n bytes
           -o  preset file offset to argument value

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   DASM mode:

   Read in a binary file. PC and file offset is changeable via command line options. Selection between
   non-segmented or segmented mode is required at command line. No segment mode change while runtime supported.
   Number of disassembly bytes can be set.

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   TestMode 1 (-t1):

   Read in a HEX file. Interprets each line as ONE Z8001 command. Missing follow up bytes are extended to zero.
   Comments are marked with '#' at begin of line and are copied to output stream
   See VERIF seq_*.src files for examples.

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   TestMode 2 (-t2):

   Read in a file of consecutive HEX codes. Newlines are allowed on word boundaries. Can be used instead of
   binary mode fore easy edit. Comments and other than hex characters are not supported. File offset is possible
   but must be entered 16bit word aligned.

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   Program Test:

   All 65536 primary opcodes have been stimulated using test mode -t2. When neccessary, follow up code has been
   added per instruction. Startup files are VERIF/seq_nonseg.src (non-segmented), VERIF/seq_short_seg.src (segmented SS)
   and VERIF/seq_long_seg.src (SL). Resulting output files containing valid, invalid and reserved codes. After
   pruning, all Z8001 opcodes are listed in seq_nonseg_pruned.lst, seq_short_seg_pruned.lst and seq_long_seg_pruned.lst.
   A report of pruned (invalide) encodings for all three mode (NS,SS,SL) can be found in prune_report_ns_ss_ls.lst

   All valid opcodes (NS/SS/SL) have been fed into P8000-UDOS U8000ASM PLZ/SYS assembler. Its list output was processed back
   into the disassembler and compared with all original encoding. This closed verification loop has been executed without 
   error.

   In theory, those invalid opcodes could be pruned out directly in a second pass of z8000_init (z8000tbl.c) to point to
   .word statements. In practice however, a correctly executed program will not encounter incorrect opcodes. Preemtively 
   fetching tools, such as a debugger or a line disassembler will need additional control information to bypass invalid
   sections. This might be supported in further versions of the line disassembler.

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