Intel 8080 CPU Emulator

    2010 by Stefan Tramm

    based on
      ShellInABox and its marvelous VT100 emulator by Markus Gutschke
	(http://code.google.com/p/shellinabox/)
      js8080 by Chris Double (http://www.bluishcoder.co.nz/js8080/)
      z80pack by Udo Munk (http://www.unix4fun.org/z80pack/)

    This program emulates a minimal Intel 8080 Microcomputer that runs CP/M.

    It supports 4 disk drives (8' CPM standard), which are stored persistently
    in the browsers local database. Disks can be mounted by the monitors
    'r' (reads from server) and 'dsk' commands (supports mounting of images
    via drag-n-drop from your host computer). A paper tape is also available,
    mount new tapes by drag-n-drop onto the main window. Modified disks and
    punched tapes can be posted to arbitrary webservers ('ptp' and 'dsk N'
    commands). The emulator is written as a web app and is therefore cached
    by your browser, therefore no further internet connection is required
    to run the emulator.
    When CPM is booted, type CTRL-. to escape to the monitor and 'g' to
    continue.
    Chrome6+ (or Safari5+) required. Firefox does not support the disk
    subsystem, as currently only WebDB is implemented.

    Start Emu8080 for the full adventure!

    --------------------

    Some Intel HEX files with demo programs, after loading the
    file with the read command 'r', start with 'g 0'.

    hello.hex  -- Hello World
    loop.hex   -- an endless loop printing dots, stop with Ctrl-.
    10mcyc.hex -- execute 10'023'517 clock cycles
    basic.hex  -- MS 8K BASIC ('g 1000' to start, 'exit' to leave)

    --------------------

    CPM and disks

    cpma.cpm  -- CP/M 2.2 boot disk
     insert the A: diskette:  'r 0 cpma' needed only once
     load boot sector to mem: 'b'
     start the boot loader:   'g 0'
     Format diskettes in drives B: to D: with 'F 1' to 'F 3'.
     For further info read the CP/M 2.2 Manual (540KB) and
     the Intel 8080-8085 Assembly Language Programming Guide (5.8MB).

    zork1.cpm -- classic adventure game
     insert the game into B: 'r 1 zork1' needed only once
     when CP/M is booted:    'b:'
                             'zork1'
     many thanks to Neozeed (http://virtuallyfun.blogspot.com/)
     for contributing the image! enjoy it :-)

    volks4th.cpm  -- Volks 4th for 8080
    volks4th2.cpm -- data disk
     insert the 4th disks: 'r 2 volks4th'
			   'r 3 volks4th2'
     when CP/M is booted:  'c:'
			   'volks4th'
     many thanks to Carsten Strotmann from 4th eV for his contribution.
     Details at forth-ev.de.

    --------------------

    Used I/O ports (decimal addresses):
 
      0 - console status
          read console 0 status:
          0xff : input available
          0x00 : no input available
 
      1 - console data
 
      2 - printer status (not implemented yet)
      3 - printer data
 
      4 - auxilary status / command
	  read  status:  0xff : input available
	  write command: 0x01 : rewind tape
      5 - auxilary data
	  read from paper tape, tapes are mounted by dropping a text file
	  write to puncher
 
     10 - FDC drive
     11 - FDC track
     12 - FDC sector
 
     13 - FDC command
          write FDC command: transfer one sector in the wanted direction,
          0 = read, 1 = write
          read FDC command: check for IO completion,
          0 = still in progress, 1 = IO done
 
     14 - FDC status
          The status byte of the FDC is set as follows:
          0 - ok
          1 - illegal drive
          2 - illegal track
          3 - illegal sector
          4 - seek error
          5 - read error
          6 - write error
          7 - illegal command to FDC
 
     15 - DMA destination address low
     16 - DMA destination address high
 
    --------------------

    The Z80 assember listing of the sector 0 boot loader
    and the Z80 assembler listing for the used BIOS.

    A simple savefile CGI to handle the upload of paper tape
    puncher files and disk images. DONT INSTALL THIS PROGRAM
    ON A PUBLIC WEBSERVER, it contains severe security holes!
    USE AT YOUR OWN RISC.

    --------------------

    The 8K BASIC is derived from the NASCOM 8K BASIC by Microsoft,
    sources are located here. For details take a look at the
    scanned manual (1.3MB). Instead of 'CSAVE' and 'CLOAD' use
    'SAVE' and 'LOAD' to save/load from the virtual papertape
    device. Use 'EXIT' to go back to the console. Don't expect
    that the screen oriented commands work.

    You can download a simple benchmark BASIC program which
    must be dropped on the terminal window to be mounted as a
    paper tape, which can be loaded from inside BASIC via 'LOAD'.
    The source is linked inside the REM lines, just click it :-)

    Have fun -- Stefan Tramm

    --------------------

    On 2013-08-20 Chris Double (@doublec) mentioned this work
    as using his 8080 emulator on Twitter. Many Thanks Chris!