xtrs(1)                                                                xtrs(1)

Name
       xtrs - TRS-80 Model I/III/4/4P emulator for the X Window System

Syntax
       xtrs [-model m] [-diskdir d] [-debug] [other options]

Description
       xtrs is built on top of a Z-80 emulator, with added routines to support
       keyboard and video I/O through an X interface.  The hardware  emulation
       can operate as a TRS-80 Model I, Model III, Model 4, or Model 4P.

       xtrs  supports 48K of RAM in Model I or Model III mode, 128K in Model 4
       or Model 4P mode.  Floppy disks and hard disks are emulated using files
       to store the data; or under Linux only, real floppy drives can be used.
       A printer is emulated by sending its  output  to  standard  output.   A
       serial  port is emulated using a Unix tty device.  Cassette I/O is emu-
       lated using files to store the cassette data; real cassettes  can  also
       be read or written (with luck), either directly through your sound card
       (on Linux and other systems with OSS-compatible sound drivers), or  via
       .wav files.  Game sound and music output are also supported if you have
       an OSS-compatible sound driver; sound output though the cassette  port,
       through  the  Model  4  sound  option, and through the optional Orches-
       tra-85/90 music synthesizer card are all emulated.  In  Model  I  mode,
       the  HRG1B  graphics card is emulated.  In Model III and 4/4P mode, you
       can select whether the Radio Shack graphics card or Micro  Labs  Grafyx
       Solution  is  emulated.   There  is  also a mouse driver for Model 4/4P
       mode.  Several common time-of-day clock cards are emulated on all  mod-
       els.   The  Alpha  Products joystick is emulated using the PC's numeric
       keypad.

       Because xtrs emulates the hardware, all known TRS-80  Model  I/III/4/4P
       operating  systems  should  run on it, including all flavors of TRSDOS,
       LDOS/LS-DOS, NEWDOS, DOSPLUS, MultiDOS, and TRS-80 CP/M.  However,  the
       emulator  also  includes  some extensions to the standard hardware, and
       the special drivers, utilities, and instructions needed for  these  are
       not provided for all operating systems.

       The  Z-80 emulator has a debugger called zbx.  You can enter the debug-
       ger either by starting xtrs with the -debug  flag  or  by  pressing  F9
       while xtrs is running.  The debugger runs in the X terminal window that
       you started xtrs from.  Once you are in the debugger, type  "help"  for
       more information.

       Special  support in the emulator allows the program to block when wait-
       ing for information from the keyboard.  This will work  only  for  pro-
       grams  that  wait for keyboard input using the standard Model I/III ROM
       call; the emulator decides whether to block the Z-80  program  when  it
       tries to read from the keyboard memory by pattern-matching its stack.

Keys
       The following keys have special meanings to xtrs:

       LeftArrow, Backspace, or Delete is the TRS-80 left arrow key.  RightAr-
       row or Tab is the right arrow key.  UpArrow is the up arrow key.   Dow-
       nArrow  or  Linefeed  is the down arrow key.  Esc or Break is the Break
       key.  Home, Clear, or LeftAlt is the Clear key.  Control is the Model 4
       Ctrl  key  (address  bit 7, data bit 2).  RightAlt is equivalent to the
       shifted down arrow key (used as a control key with  some  TRS-80  soft-
       ware).

       F1,  F2,  and  F3 are the Model 4/4P function keys (address bit 7, data
       bits 4, 5, and 6).  F1 is also the Model I Electric Pencil control  key
       that  some  users added to their machines.  F4 is the Model 4 Caps Lock
       key (address bit 7, data bit 3).  F5, Compose, or ScrollLock is equiva-
       lent  to  the  @  key (so that @ can be used as a modifier key).  F6 is
       equivalent to the 0 key (so that a shifted 0 can be obtained).  F7 sig-
       nals a disk change in the emulated floppy drives (see below).  F8 exits
       the program.  F9 enters the debugger (zbx).  F10 is the reset button.

       In Model III, 4, and 4P modes, the left and right shift keys  are  dis-
       tinct;  in  Model  I  mode, they are the same.  The PageUp and PageDown
       keys always  activate  the  positions  that  correspond  to  the  Model
       III/4/4P  left  and  right shift keys (address bit 7, data bits 0 and 1
       respectively), even in Model I mode.  The End key activates  an  unused
       position in the keyboard matrix (address bit 7, data bit 7).

       The  keys  [, \, ], ^,  , {, |, }, and ~ also activate unused positions
       in the keyboard matrix (address bit  3,  data  bits  3-7).   With  many
       TRS-80  keyboard  drivers,  these  keys  map to the corresponding ASCII
       characters; with others, they do nothing.  In some cases you  may  find
       the  shift state is reversed from what it should be; if you press [ but
       { is displayed instead (etc.),  see  the  -shiftbracket  and  -noshift-
       bracket  options  below to correct the problem.  The Insert key maps to
       the same position as underscore (address bit 3, data bit  7),  so  that
       this  key  can  be  used both with and without shift pressed; with many
       TRS-80 keyboard drivers one of these maps to ASCII code 0x7f.

       On a German keyboard, the umlaut and "ess-tsett" keys  should  activate
       the corresponding characters used in the GENIE, a German Model I clone.
       This feature is most useful together with the "-charset genie"  command
       line argument.

       Pressing  a key on a PC numeric keypad with NumLock disengaged emulates
       the Alpha Products joystick.   Keys  2,  4,  6,  8  (KP Down,  KP Left,
       KP Right,  KP Up) are the main directions; keys 1, 3, 7, and 9 (KP End,
       KP Page Down, KP Home, KP Page Up) work as diagonal directions by acti-
       vating  two  main  directions  at  once;  and  key  0  (KP Insert) or 5
       (KP Begin) is the fire button.  Note that your X server may default  to
       sending  digits  for the keys on the numeric pad even if NumLock is not
       pressed.  If you have this problem, you can use the xmodmap program  to
       remap your numeric pad, and use the xev program to debug it.

Emulated cassette
       To  control the emulated cassette, a file called ".cassette.ctl" in the
       current directory keeps track of what file is currently loaded  as  the
       cassette  tape  and  the  current  position within that file.  The cas-
       sette(1) shell script provides a way to manipulate this file.  You  may
       use  this  script to load and position cassette tape files.  The opera-
       tion works very much like an actual tape recorder.   See  the  cassette
       man  page  for more information about the cassette shell script and the
       cassette file formats that are supported.

Printer
       For printer support, any text  sent  to  the  TRS-80's  printer  (using
       LPRINT or LLIST, for example) is sent to the standard output.

Emulated floppy disks
       In  Model  I mode, xtrs emulates a Radio Shack Expansion Interface with
       the Percom Doubler or Radio Shack Doubler installed.  The Doubler  pro-
       vides  double-density  disk  access by allowing either the stock WD1771
       FDC chip or a WD1791 chip to be selected  under  program  control.   At
       powerup  the  1771  is  selected,  so operating systems with no Doubler
       driver see a stock system.  By default, the  emulator  pretends  to  be
       both  a  Percom and Radio Shack Doubler at the same time -- it responds
       to the special commands of both -- so a driver for either should  work.
       Under  LDOS,  use  the  command  "FDUBL"  (newer  versions of LDOS), or
       "PDUBL" or "RDUBL" (older versions) to  install  the  driver.  Software
       that tries to detect which doubler you have (such as Super Utility) may
       be confused by the emulation of both at once, so you can choose to emu-
       late only one with a command line option; see below.

       In Model III, 4, or 4P mode, xtrs emulates the stock floppy controller,
       which uses a WD1793 chip (software-compatible with the WD1791) to  pro-
       vide both single and double density.

       Four  5.25-inch floppy drives are emulated, with storage in files named
       diskM-U, where M is the TRS-80 model (1, 3, 4, or  4p)  and  U  is  the
       drive  unit  number (0, 1, 2, or 3).  If a file of the required name is
       not found, a drive with no disk in it is emulated (but see below).   If
       the  user  does not have write permission for a floppy file, and/or the
       file has an internal write protect flag set,  a  write-protect  tab  is
       emulated.   Use the mkdisk(1) program to turn the write protect flag on
       or off.  To change floppies in an emulated drive, rename  the  existing
       file  for  the drive (if any), rename the new floppy file to the proper
       name, and hit function key F7 in the emulator.

       If you try to boot an emulated Model I, III, or 4 with  no  file  named
       diskM-0  (that  is, no disk in drive 0), xtrs emulates having no floppy
       disk controller.  The behavior of a real machine with a disk controller
       in  this  case didn't seem useful to emulate faithfully: A real Model I
       hangs with a screen full of garbage; a real Model III or 4 goes into  a
       retry  loop  printing  "Diskette?" on the screen and rechecking whether
       you've inserted one.  A real Model 4P always has a  floppy  controller,
       however, so xtrs always emulates one.

       Due  to  a limitation of the original Model I hardware, drive :3 cannot
       be double-sided in Model I mode.  In the original Model  I,  you  could
       not have a drive :3 at all if any drive in the system was double-sided,
       but the emulator is able to be more forgiving.

       Emulated floppy image files can be of any of three types: JV1, compati-
       ble  with Jeff Vavasour's popular freeware Model I emulator for MS-DOS;
       JV3, a compatible extension of a format first used in  Vavasour's  com-
       mercial  Model  III/4  emulator;  or  DMK, compatible with David Keil's
       Model 4 emulator.  All three types work  in  xtrs  regardless  of  what
       model  it  is  emulating.   A heuristic is used to decide which type of
       image is in a drive, as none of the types has a magic number or  signa-
       ture.

       JV1 supports only single density, single sided, with directory on track
       17.  Sectors must be 256 bytes long.  Use FORMAT (DIR=17) if  you  want
       to format JV1 disks with more (or less) than 35 tracks under LDOS.

       JV3  is much more flexible, though it still does not support everything
       the real controllers could do.  It is probably best to use JV3 for  all
       the  disk images you create, since it is the most widely implemented by
       other emulators, unless you have a special reason to  use  one  of  the
       others.   A  JV3 disk can be formatted with 128, 256, 512, or 1024-byte
       sectors, 1 or 2 sides, single or double density, with either  FB  (nor-
       mal)  or  F8 (deleted) data address mark on any sector.  In single den-
       sity the nonstandard data address marks FA and F9 are  also  available.
       You  cannot format a sector with an incorrect track number or head num-
       ber.  You can format a sector with an intentional CRC error in the data
       field.  xtrs supports at most 5802 total sectors on a JV3 image.

       The  original  Vavasour JV3 format supported only 256-byte sectors, and
       had a limit of 2901 total sectors.  If you use sector sizes other  than
       256  bytes  or format more than 2901 sectors on a disk image, emulators
       other than xtrs may be unable to read it.  Note that an 80 track,  dou-
       ble-sided,  double-density (18 sector) 5.25-inch floppy will fit within
       the original 2901 sector limit; the extension to 5802 is primarily  for
       emulation of 8-inch drives (discussed below).

       The  DMK  format  is the most flexible.  It supports essentially every-
       thing that the original hardware could do,  including  all  "protected"
       disk  formats.   However, a few protected disks still may not work with
       xtrs due to limitations in  xtrs's  floppy  disk  controller  emulation
       rather  than limitations of the DMK format; see the LIMITATIONS section
       below.

       The program mkdisk(1) makes a blank emulated floppy or "bulk erases" an
       existing  one.   By default, mkdisk makes a JV3 floppy, but with the -1
       flag it makes a JV1 floppy, or with the -k flag a DMK floppy.  See  the
       mkdisk man page for more information.

       Early  Model  I  operating systems used an FA data address mark for the
       directory on single density disks, while later ones wrote F8 but  would
       accept either upon reading.  The change was needed because FA is a non-
       standard DAM that is fully supported only by  the  WD1771  floppy  disk
       controller  used in the Model I; the controllers in the Model III and 4
       cannot distinguish between FA and FB (which is used  for  non-directory
       sectors)  upon  reading, and cannot write FA.  To deal nicely with this
       problem, xtrs implements the following kludge.  On  writing  in  single
       density, an F8 data address mark is recorded as FA.  On reading with an
       emulated WD1771 (available in Model I mode only), FA is returned as FA;
       on  reading  with a WD179x, FA is returned as F8.  This trick makes the
       different operating systems perfectly compatible with each other, which
       is  better  than  on  a real Model I!  You can use the -truedam flag to
       turn off this kludge if you need to; in that case the original hardware
       is emulated exactly.

       TRS-80  programs  that attempt to measure the rotational speed of their
       floppy disk drives using timing loops will get the answers they expect,
       even  when  xtrs does not emulate instructions at the same speed as the
       original machines. This works because xtrs keeps a virtual clock (tech-
       nically,  a  T-state  counter),  which measures how much time it should
       have taken to execute the instruction stream on a real machine, and  it
       ties  the  emulation  of  floppy disk index holes to this clock, not to
       real time.

Emulated 8-inch floppy disks
       In addition to the four standard 5.25-inch drives, xtrs  also  emulates
       four  8-inch floppy drives.  There is no widely-accepted standard hard-
       ware interface for 8-inch floppies on the TRS-80, so  xtrs  emulates  a
       pseudo-hardware interface of its own and provides an LDOS/LS-DOS driver
       for it.

       Storage for the emulated 8-inch disks is in files named diskM-U,  where
       M  is  the  TRS-80 model number (1, 3, 4, or 4p) and U is a unit number
       (4, 5, 6, or 7).  The only difference between 5.25-inch and 8-inch emu-
       lated  drives  is that the emulator allows you to format more bytes per
       track in the latter.  A new JV3  floppy  can  be  formatted  as  either
       5.25-inch  or  8-inch  depending on whether you initially put it into a
       5.25-inch or 8-inch emulated drive.  A new DMK floppy, however, must be
       created  with the -8 flag to mkdisk in order to be large enough for use
       in an 8-inch emulated drive.  JV1 floppies cannot  be  used  in  8-inch
       drives.  Be careful not to put an emulated floppy into a 5.25-inch emu-
       lated drive after it has been formatted in an 8-inch emulated drive  or
       vice  versa;  the  results  are likely to be confusing.  Consider using
       different file extensions for the two types; say,  .dsk  for  5.25-inch
       and .8in for 8-inch.

       To use the emulated 8-inch drives, you'll need a driver.  Under LDOS or
       LS-DOS, use the program XTRS8/DCT supplied on the emulated floppy util-
       ity.dsk.   This  driver  is  a  very  simple  wrapper around the native
       LDOS/LS-DOS floppy driver.  Here are detailed instructions.

       First, make sure an appropriate version of LDOS is in  emulated  floppy
       drive  0,  and  the  supplied  file  utility.dsk is in another emulated
       floppy drive.  Boot LDOS.  If you are using Model I LDOS, be sure FDUBL
       is running.

       Second,  type  the following commands.  Here d is the LDOS drive number
       you want to use for the 8-inch drive and u is the unit number you chose
       when  naming the file.  Most likely you will choose d and u to be equal
       to reduce confusion.

           SYSTEM (DRIVE=d,DRIVER="XTRS8",ENABLE)
           Enter unit number ([4]-7): u

       You can repeat these steps with different values of d  and  u  to  have
       more  than one 8-inch drive.  You might want to repeat four times using
       4, 5, 6, and 7, or you might want to save some drive numbers  for  hard
       drives (see below).

       Finally,  it's  a  good idea to give the SYSTEM (SYSGEN) command (Model
       I/III) or SYSGEN command (Model 4/4P).  This command saves  the  SYSTEM
       settings,  so  the  8-inch drives will be available again the next time
       you reboot or restart the emulator.  If you need to  access  an  8-inch
       drive  after  booting from a disk that hasn't been SYSGENed, simply use
       the same SYSTEM command again.

       In case you want to write your own driver for another TRS-80  operating
       system,  here  are details on the emulated pseudo-hardware.  The 8-inch
       drives are accessed through the normal floppy disk controller,  exactly
       like  5.25-inch drives.  The four 5.25-inch drives have hardware select
       codes 1, 2, 4, and 8, corresponding respectively to files diskM-0,  -1,
       -2, and -3.  The four 8-inch drives have hardware select codes 3, 5, 6,
       and 7, corresponding respectively to files diskM-4,  -5,  -6,  and  -7.
       (See also the -sizemap option below, however.)

Real floppy disks
       Under  Linux  only,  any  diskM-U file can be a symbolic link to a real
       floppy disk drive, typically /dev/fd0 or /dev/fd1.  Most PCs should  be
       able to read and write TRS-80 compatible floppies in this way.  Many PC
       floppy controllers cannot handle single density, however, and some  may
       have  problems even with double density disks written on a real TRS-80,
       especially disks formatted by older TRS-80 operating systems.  Use  the
       -doublestep  flag  if you need to read 35-track or 40-track media in an
       80-track drive.  If you need to write 35-track or 40-track media in  an
       80-track  drive,  bulk-erase  the  media  first  and  format  it in the
       80-track drive.  Don't write to a disk in an 80-track drive if  it  has
       ever been written to in a 40-track drive.  The narrower head used in an
       80-track drive cannot erase the full track width written by the head in
       a 40-track drive.

       If you link one of the 5.25-inch floppy files (diskM-0 through diskM-3)
       to a real floppy drive, TRS-80 programs will  see  it  as  a  5.25-inch
       drive,  but  the actual drive can be either 3.5-inch or 5.25-inch.  The
       drive will be operated in double density (or single density), not  high
       density, so be sure to use the appropriate media.

       If you link one of the 8-inch floppy files (diskM-4 through diskM-7) to
       a real floppy drive, TRS-80 programs will see it as  an  8-inch  drive.
       Again,  you  need to use the XTRS8/DCT driver described above to enable
       LDOS/LS-DOS to access an 8-inch drive.  The real drive  can  be  either
       3.5-inch,  5.25-inch, or 8-inch.  A 3.5-inch or 5.25-inch drive will be
       operated in high-density mode, using MFM recording  if  the  TRS-80  is
       trying to do double density, FM recording if the TRS-80 is trying to do
       single density.  In this mode, these drives can hold as much data as  a
       standard 8-inch drive.  In fact, a 5.25-inch HD drive holds exactly the
       same number of bits per track as an 8-inch drive; a 3.5-inch  HD  drive
       can hold 20% more, but we waste that space when using one to emulate an
       8-inch drive.  In both cases we also waste the top three tracks,  since
       an 8-inch drive has only 77 tracks, not 80.

       The  nonstandard  FA and F9 data address marks available in single den-
       sity on a real Model I with the WD1771  controller  also  need  special
       handling.  A PC-style floppy disk controller can neither read nor write
       sectors with such DAMs at all.  This raises three issues: (1)  It  will
       be  impossible  for  you  to read some Model I disks on your PC even if
       your PC otherwise supports single density.  In particular, Model I TRS-
       DOS  2.3 directory tracks will be unreadable.  (2) On writing in single
       density, xtrs silently records a F9 or FA DAM as F8.  (3) On reading in
       single  density  with  an  emulated  WD1771  (Model I mode only), F8 is
       returned as FA.  If you need more accurate behavior, the -truedam  flag
       will turn on error messages on attempts to write F9 or FA DAMs and will
       turn off translation of F8 to FA on reading.

       Hint: Be sure to set the drive type correctly in your PC's BIOS.  Linux
       and  xtrs  rely  on  this  information to know how fast your drives are
       spinning and hence what data rate to use when reading and writing.  All
       3.5-inch  drives spin at 300 RPM.  Newer 5.25-inch high-density capable
       drives ("1.2MB" drives) normally always spin at 360 RPM.  (Some can  be
       jumpered  to  slow down to 300 RPM when in double-density mode, but you
       should not do that when plugging  one  into  a  PC.)   Older  5.25-inch
       drives  that  cannot  do  high  density  ("180KB",  "360KB"  or "720KB"
       5.25-inch drives) always spin at 300 RPM.  All 8-inch  drives  spin  at
       360 RPM.  If you plug an 8-inch drive into a PC (this requires a 50-pin
       to 34-pin adaptor cable), tell your BIOS that it is a  5.25-inch  1.2MB
       drive.

Emulated hard disks
       xtrs can emulate a hard disk in a file in one of two ways: it can use a
       special, xtrs-specific LDOS driver called XTRSHARD/DCT, or it can  emu-
       late  the Radio Shack hard drive controller (based on the Western Digi-
       tal WD1010) and use the native drivers for the original hardware.

       Using XTRSHARD/DCT

       The XTRSHARD/DCT driver has been tested and works under both LDOS 5.3.1
       for  Model  I or III and TRSDOS/LS-DOS 6.3.1 for Model 4/4P.  It may or
       may not work under earlier LDOS versions.  It definitely will not  work
       under other TRS-80 operating systems or with emulators other than xtrs.
       The hard disk format was designed by Matthew Reed for his  Model  I/III
       and  Model  4  emulators;  xtrs duplicates the format so that users can
       exchange hard drive images across the emulators.

       To use XTRSHARD/DCT, first run the mkdisk program under Unix to  create
       a  blank  hard  drive  (.hdv)  file.  Typical usage would be: mkdisk -h
       mydisk.hdv.  See the mkdisk(1) man page for other options.

       Second, link the file to an appropriate name.  XTRSHARD/DCT supports up
       to  eight  hard  drives, with names of the form hardM-U, where M is the
       TRS-80 model (1, 3, or 4; in this case Model 4P also uses M=4) and U is
       a unit number from 0 to 7.  It looks for these files in the same direc-
       tory as the floppy disk files diskM-U.

       Third, make sure an appropriate version of LDOS is in  emulated  floppy
       drive  0,  and  the  supplied  file  utility.dsk is in another emulated
       floppy drive.  Boot LDOS.  If you are using Model I LDOS 5.3.1, patch a
       bug  in  the  FORMAT  command by typing PATCH FORMAT/CMD.UTILITY M1FOR-
       MAT/FIX.  You need to apply this patch  only  once.   It  must  not  be
       applied to Model III or Model 4/4P LDOS.

       Fourth,  type  the following commands.  Here d is the LDOS drive number
       you want to use for the hard drive (a typical choice would be 4) and  u
       is the unit number you chose when naming the file (most likely 0).

           SYSTEM (DRIVE=d,DRIVER="XTRSHARD",ENABLE)
           Enter unit number ([0]-7): u
           FORMAT d (DIR=1)

       Answer  the questions asked by FORMAT as you prefer.  The DIR=1 parame-
       ter to FORMAT is optional; it causes the hard drive's directory  to  be
       on  track  1,  making  the  initial size of the image smaller.  You can
       repeat these steps with different values of d and u to have  more  than
       one hard drive.

       Finally,  it's  a  good idea to give the SYSTEM (SYSGEN) command (Model
       I/III) or SYSGEN command (Model 4/4P).  This command saves  the  SYSTEM
       settings, so the drive will be available again the next time you reboot
       or restart the emulator.  If you need to  access  the  hard  disk  file
       after  booting  from a floppy that hasn't been SYSGENed, simply use the
       same SYSTEM command(s) again, but don't FORMAT.  You can freely  use  a
       different drive number or (if you renamed the hard disk file) a differ-
       ent unit number.

       The F7 key currently doesn't allow XTRSHARD/DCT disk changes to be rec-
       ognized,  but you can change to a different hard disk file for the same
       unit by renaming files as needed and rebooting LDOS.

       Technical note: XTRSHARD/DCT is a small Z-80  program  that  implements
       all  the required functions of an LDOS disk driver.  Instead of talking
       to a real (or emulated) hard disk controller, however, it uses  special
       support  in  xtrs  that  allows Z-80 programs to open, close, read, and
       write Unix files directly.  This support is described  further  in  the
       "Data import and export" section below.

       Using native hard disk drivers

       Beginning  in version 4.1, xtrs also emulates the Radio Shack hard disk
       controller (based on the Western Digital WD1010) and will work with the
       native  drivers  for  this hardware.  This emulation uses the same hard
       drive (.hdv) file format that XTRSHARD/DCT does.  With LDOS/LS-DOS, the
       RSHARDx/DCT  and  TRSHD/DCT  drivers are known to work.  With Montezuma
       CP/M 2.2, the optional Montezuma hard disk drivers are known  to  work.
       The hard disk drivers for NEWDOS/80 and for Radio Shack CP/M 3.0 should
       work, but they have not yet been tested  at  this  writing.   Any  bugs
       should be reported.

       To  get  started,  run  the mkdisk program under Unix to create a blank
       hard drive (.hdv) file.  Typical usage would be: mkdisk -h  mydisk.hdv.
       See the mkdisk(1) man page for other options.

       Second,  link  the  file  to an appropriate name.  The WD1010 emulation
       supports up to four hard drives, with names of the form hardM-U,  where
       M is the TRS-80 model (1, 3, 4, or 4p) and U is a unit number from 0 to
       3.  It looks for these files in the same directory as the  floppy  disk
       files  diskM-U.  If no such files are present, xtrs disables the WD1010
       emulation.

       Note that if hard  drive  unit  0  is  present  on  a  Model  4P  (file
       hard4p-0),  the  Radio  Shack boot ROM will always try to boot from it,
       even if the operating system does  not  support  booting  from  a  hard
       drive.   If you have this problem, either hold down F2 while booting to
       force the ROM to boot from floppy, or simply avoid using unit number 0.
       Stock TRSDOS/LS-DOS 6 systems do not support booting from a hard drive;
       M.A.D. Software's HBUILD6 add-on  to  LS-DOS  for  hard  drive  booting
       should  work,  but  is untested.  Montezuma CP/M 2.2 does boot from the
       emulated hard drive.

       Finally, obtain the correct driver for the operating system you will be
       using,  read  its  documentation,  configure the driver, and format the
       drive.  Detailed instructions are beyond the scope of this manual page.

Data import and export
       Several  Z-80  programs  for data import and export from various TRS-80
       operating systems are included with xtrs on two emulated floppy images.
       These  programs  use  special support in the emulator to read and write
       external Unix files, discussed further at the end of this section.

       The emulated floppy utility.dsk contains some programs for transferring
       data  between  the  emulator  and  ordinary  Unix  files.   IMPORT/CMD,
       EXPORT/CMD, and SETTIME/CMD run on the emulator under Model I/III  TRS-
       DOS, Model I/III LDOS, Model I/III Newdos/80, and Model 4/4P TRSDOS/LS-
       DOS 6; they may also work under other TRS-80 operating systems.   Model
       III  TRSDOS  users  will  have  to use TRSDOS's CONVERT command to read
       utility.dsk.

       IMPORT/CMD imports a Unix file and  writes  it  to  an  emulated  disk.
       Usage:  IMPORT  [-lne]  unixfile  [trsfile].  The -n flag converts Unix
       newlines (\n) to TRS-80 newlines (\r).  The -l flag converts  the  Unix
       filename to lower case, to compensate for TRS-80 operating systems such
       as Newdos/80 that convert all command line  arguments  to  upper  case.
       When using the -l flag, you can put a [ or up-arrow in front of a char-
       acter to keep it in upper case.  Give the -e flag if your TRS-80  oper-
       ating  system uses the Newdos/80 convention for representing the ending
       record number in an open file control block.  This should  be  detected
       automatically  for Newdos/80 itself and for TRSDOS 1.3, but you'll need
       to give the flag for DOSPLUS and possibly other non-LDOS operating sys-
       tems.  If you need the flag but don't give it (or vice versa), imported
       files will come out the wrong length.  If the destination file is omit-
       ted,  IMPORT uses the last component of the Unix pathname, but with any
       "." changed to "/" to match TRS-80 DOS file extension syntax.

       EXPORT/CMD reads a file from an emulated disk and exports it to a  Unix
       file.  Usage:  EXPORT  [-lne] trsfile [unixfile].  The -n flag converts
       TRS-80 newlines (\r) to Unix newlines (\n).  The -l flag  converts  the
       Unix  filename  to lower case.  When using the -l flag, you can put a [
       or up-arrow in front of a character to keep it in upper case.  Give the
       -e  flag  if your TRS-80 operating system uses the Newdos/80 convention
       for representing the ending record  number  in  an  open  file  control
       block.   This should be detected automatically for Newdos/80 itself and
       for TRSDOS 1.3, but you'll need to give the flag for DOSPLUS and possi-
       bly  other  non-LDOS operating systems.  If you need the flag but don't
       give it (or vice versa), exported files will come out the wrong length.
       If  the  destination  file is omitted, EXPORT uses the TRS-80 filename,
       but with any "/" changed to "." to match Unix file extension syntax.

       SETTIME/CMD reads the date and time from Unix and sets the TRS-80 DOS's
       date and time accordingly.

       The  next  several  programs were written in Misosys C and exist in two
       versions on utility.dsk.  The one whose name ends in "6" runs on  Model
       4  TRSDOS/LS-DOS  6.x;  the other runs on LDOS 5.x and most other Model
       I/III operating systems.

       CD/CMD (or CD6/CMD) changes xtrs's Unix working directory.   Usage:  CD
       [-l]  unixdir.   The  -l flag converts the Unix directory name to lower
       case.  When using the -l flag, you can put a [ or up-arrow in front  of
       a  character  to keep it in upper case.  Running CD/CMD will change the
       interpretation of any relative pathnames given to IMPORT or EXPORT.  It
       will  also  change  the  interpretation  of disk names at the next disk
       change, unless you specified an absolute pathname for  xtrs's  -diskdir
       parameter.

       PWD/CMD (or PWD6/CMD) prints xtrs's Unix working directory.

       UNIX/CMD  (or  UNIX6/CMD)  runs a Unix shell command.  Usage: UNIX [-l]
       unix command line.  The -l flag converts the Unix command line to lower
       case.   When using the -l flag, you can put a [ or up-arrow in front of
       a character to keep it in upper case.  Standard  I/O  for  the  command
       uses the xtrs program's standard I/O descriptors; it does not go to the
       TRS-80 screen or come from the TRS-80 keyboard.

       MOUNT/CMD (or MOUNT6/CMD) is a convenience program that  switches  emu-
       lated  floppy  disks in the drives.  Usage: MOUNT [-l] filename U.  The
       -l flag converts the Unix filename to lower case.  When  using  the  -l
       flag, you can put a [ or up-arrow in front of a character to keep it in
       upper case.  The filename is any Unix filename; U is a single digit,  0
       through 7.  The command deletes the file diskM-U (where M is the TRS-80
       model) from the disk directory (see -diskdir option), replaces it  with
       a symbolic link to the given filename, and signals a disk change (as if
       F7 had been pressed).

       UMOUNT/CMD (or UMOUNT6/CMD) is a convenience program  that  removes  an
       emulated  floppy  disk  from  a drive.  Usage: UMOUNT U.  U is a single
       digit, 0 through 7.  The command deletes the file diskM-U (where  M  is
       the  TRS-80  model)  from  the disk directory (see -diskdir option) and
       signals a disk change (as if F7 had been pressed).

       The emulated floppy cpmutil.dsk contains import and export programs for
       Montezuma CP/M, written by Roland Gerlach.  It was formatted as a "Mon-
       tezuma Micro Standard DATA disk (40T, SS,  DD,  200K),"  with  512-byte
       sectors.   Be  careful to configure your CP/M to the proper disk format
       and drive parameters (40 track, not 80), or  you  will  have  confusing
       problems  reading  this  disk.   Documentation  is included in the file
       cpmutil.html and source code in the file cpmutil.tgz (a gzipped tar ar-
       chive).     See   http://members.optusnet.com.au/~rgerlach/trs-80/cpmu-
       til.html where you will sometimes find a newer version of the utilities
       than is included with xtrs.

       The  emulator  implements a set of pseudo-instructions (emulator traps)
       that give TRS-80 programs access to Unix files.   The  programs  listed
       above use them.  If you would like to write your own such programs, the
       traps are documented in the file trs imp exp.h.  Assembler source  code
       for   the  existing  programs  is  supplied  in  xtrshard.z,  import.z,
       export.z, and settime.z.  You can also  write  programs  that  use  the
       traps  in  Misosys  C,  using the files xtrsemt.h and xtrsemt.ccc as an
       interface; a simple example is in settime.ccc.

Interrupts
       The emulator supports only interrupt mode 1.  It will complain if  your
       program  enables  interrupts  after  powerup  without executing an IM 1
       instruction first.  All Model I/III/4/4P software  does  this,  as  the
       built-in peripherals in these machines support only IM 1.

       The  Model I has a 40 Hz heartbeat clock interrupt, while the Model III
       uses 30 Hz, and the Model 4/4P can run at either 30 Hz or 60  Hz.   The
       emulator  approximates  this  rather  well even on a system where clock
       ticks come at some frequency that isn't divisible by the emulated  fre-
       quency  (e.g., 100 Hz on Intel Linux), as long as the true frequency is
       not slower than the emulated frequency.  The emulator has a  notion  of
       the  absolute time at which each tick is supposed to occur, and it asks
       the host system to wake it up at each of those times.  The  net  result
       is  that some ticks may be late, but there are always the proper number
       of ticks per second.  For example, running in Model  I  mode  on  Intel
       Linux  you'd  see this pattern: (tick, 30ms, tick, 20ms,...) instead of
       seeing ticks every 25ms.

Processor speed selection
       A standard Model 4 has a software-controlled switch to select operation
       at  either  4.05504  MHz (with heartbeat clock at 60 Hz) or 2.02752 MHz
       (with heartbeat clock at 30 Hz).  xtrs emulates this feature.

       Model I's were often modified to operate  at  higher  speeds  than  the
       standard  1.77408  MHz.   With  one common modification, writing a 1 to
       port 0xFE would double the speed to 3.54816  MHz,  while  writing  a  0
       would  set the speed back to normal.  The heartbeat clock runs at 40 Hz
       in either case.  xtrs emulates this feature as well.

Sound
       Sound support uses the Open Sound System /dev/dsp device,  standard  on
       Linux  and available on many other Unix versions as well.  This support
       is compiled in automatically on Linux; if you have OSS on another  ver-
       sion  of  Unix, you'll need to define the symbol HAVE OSS in your Make-
       file or in trs cassette.c.  Any time TRS-80  software  tries  to  write
       non-zero  values to the cassette port (or the Model 4/4P optional sound
       port) with the cassette motor off, it is assumed to be trying  to  make
       sounds  and  xtrs  opens  /dev/dsp.  It automatically closes the device
       again after a few seconds of silence.

       If you are playing a game with sound, you'll want to use the -autodelay
       flag to slow down instruction emulation to approximately the speed of a
       real TRS-80.  If you don't do this, sound will  still  play  correctly,
       but the gameplay may be way too fast and get ahead of the sound.

       On  the other hand, if your machine is a bit too slow, you'll hear gaps
       and pops in the sound when the TRS-80 program lags behind the demand of
       the  sound  card  for  more samples.  The -autodelay feature includes a
       small speed boost whenever a sound starts to play  to  try  to  prevent
       this, but if the boost is too much or too little, you might either find
       that the game runs too fast when a lot of sound is playing, or that the
       sound  has  gaps  in  it  anyway.   If your sound has gaps, you can try
       reducing the sample rate with the -samplerate flag.

       The Orchestra-85 music synthesis software will run under xtrs's Model I
       emulation,  and the Orchestra-90 software will run with Model III oper-
       ating systems under xtrs's Model III, 4, or  4P  emulation.   For  best
       results,  use  Orchestra-90 and the Model 4 emulation, as this lets the
       software run at the highest emulated clock rate (4 MHz) and thus gener-
       ate  the  best sound.  If you want to run Orchestra-85 instead, you can
       tell it that you have a 3.5 MHz  clock  speedup  with  enable  sequence
       3E01D3FE  and disable sequence 3E00D3FE; this will let the software run
       twice as fast as on an unmodified Model I and  generate  better  sound.
       There  is  no  need  to use xtrs's -autodelay flag when running Orches-
       tra-85/90, but you might want to specify a small fixed  delay  to  keep
       from getting excessive key repeat.

Mouse
       A  few Model 4 programs could use a mouse, such as the shareware hi-res
       drawing program MDRAW-II. The program XTRSMOUS/CMD on the utility  disk
       (utility.dsk)  is  a  mouse driver for Model 4/4P mode that should work
       with most such programs.  xtrs does not emulate the actual mouse  hard-
       ware  (a  serial  mouse  plugged  into the Model 4 RS-232 port), so the
       original mouse drivers will not work  under  xtrs.   Instead,  XTRSMOUS
       accesses  the  X mouse pointer using an emulator trap.  XTRSMOUS imple-
       ments the same TRSDOS/LS-DOS 6 SVC interface as  the  David  Goben  and
       Matthew Reed mouse drivers. (It does not implement the interface of the
       older Scott McBurney mouse driver, which may be required by  some  pro-
       grams.)

       By  default  XTRSMOUS  installs  itself  in  high  memory. This is done
       because MDRAW-II tests for the presence of a mouse by  looking  to  see
       whether  the  mouse  SVC  is  vectored to high memory. If the driver is
       installed in low memory, MDRAW thinks it is not there at  all.  If  you
       use  mouse-aware  programs that don't have this bug, or if you edit the
       first line of MDRAW to remove the test, you can install XTRSMOUS in low
       memory using the syntax "XTRSMOUS (LOW)".

Time of day clock
       Several  battery-backed  time  of  day clocks were sold for the various
       TRS-80 models, including the  TimeDate80,  TChron1,  TRSWatch,  and  T-
       Timer.  They are essentially all the same hardware, but reside at a few
       different port ranges.  xtrs currently emulates  them  at  port  ranges
       0x70-0x7C and 0xB0-0xBC.  The T-Timer port range at 0xC0-0xCC conflicts
       with the Radio Shack hard drive controller and is not emulated.

       These clocks return only a 2-digit year, and it is unknown  what  their
       driver software will do in the year 2000 and beyond.  If you have soft-
       ware that works with one of them, please send email to report what hap-
       pens when it is used with xtrs.

       Also  see SETTIME/CMD in the "Data import and export" section above for
       another way to get the correct time into a Z-80 operating  system  run-
       ning under xtrs.

       Finally,  you  might notice that LDOS/LS-DOS always magically knows the
       correct date when you boot it (but not the time).  When you first power
       up  the  emulated TRS-80, xtrs dumps the date into the places in memory
       where LDOS and LS-DOS normally save it across reboots, so it  looks  to
       the operating system as if you rebooted after setting the date.

Joystick
       Pressing  a key on a PC numeric keypad with NumLock disengaged emulates
       the Alpha Products joystick.  See the Keys section above  for  details.
       The emulated joystick is mapped only at port 0, to avoid conflicts with
       other devices.  The joystick emulation could be made to work with  real
       joysticks using the X input extension, but this is not implemented yet.

Running games
       Some games run rather well under xtrs now, provided that  your  machine
       is  fast  enough  to run the emulation in real time and that you choose
       the right command line options.  "Galaxy Invaders Plus" by Big 5  Soft-
       ware is particularly good.  You will usually want to turn on autodelay,
       and if your machine is slow you may need to  reduce  the  sound  sample
       rate.   Running your X server in 8-bit/pixel mode also seems to help in
       some cases. Example command lines:

           startx -- -bpp 8
           xtrs -autodelay

       If you have a slow machine and the sound breaks up, it is possible that
       your machine is not fast enough to generate samples at the default rate
       of 44,100 Hz.  If you think this may  be  happening,  try  "-samplerate
       11025" or even "-samplerate 8000".

Options
       Defaults for all options can be specified using the standard X resource
       mechanism, and the class name for xtrs is "Xtrs".

       -display display
              Set your X display to display. The default is to use the DISPLAY
              environment variable.

       -iconic
              Start with the xtrs window iconified.

       -background color
       -bg color
              Specifies the background color of the xtrs window.

       -foreground color
       -fg color
              Specifies the foreground color of the xtrs window.

       -title titletext
              Use  titletext  in  the  window title bar instead of the program
              name.

       -borderwidth width
              Put a border of width pixels around  the  TRS-80  display.   The
              default is 2.

       -scale xfac[,yfac]
              Multiply  the  horizontal  and  vertical window size by xfac and
              yfac, respectively.  Possible values are integers in  the  range
              [1,4]  for  xfac  and  [1,8]  for yfac.  Defaults are xfac=1 and
              yfac=2*xfac.

       -resize
              In Model III or 4/4P mode, resize the X window whenever the emu-
              lated display mode changes between 64x16 text (or 512x192 graph-
              ics) and 80x24 text (or 640x240 graphics).  This is the  default
              in  Model  III  mode,  since 80x24 text is not available and the
              640x240 graphics add-on card is seldom used.

       -noresize
              In Model III or 4/4P mode, always keep the X window large enough
              for  80x24  text  or  640x240  graphics,  putting a blank margin
              around the outside when the emulated display mode is 64x16  text
              or  512x192  graphics.   This is the default in Model 4/4P mode,
              since otherwise there is an annoying size  switch  during  every
              reboot.

       -charset name
              Select among several sets of built-in character bitmaps.

              In Model I mode, five sets are available. The default, wider, is
              a modified Model III set with characters 8 pixels wide; it looks
              better  on  a modern computer screen with square pixels than the
              real Model I fonts, which were 6 pixels wide. lcmod is the char-
              acter  set  in the replacement character generator that was sup-
              plied with the Radio Shack lower  case  modification.   (It  was
              reconstructed  partly  from  memory  and may have some minor bit
              errors.)  stock is the character set in the stock character gen-
              erator  supplied  with most upper case only machines. Since xtrs
              currently always emulates the extra bit of display memory needed
              to  support lower case, this character set gives you the authen-
              tic, unpleasant effect that real Model I  users  saw  when  they
              tried  to do homebrew lower case modifications without replacing
              the character generator: lower case letters appear at an  incon-
              sistent height, and if you are using the Level II BASIC ROM dis-
              play driver, upper case letters are replaced by meaningless sym-
              bols.   early  is the same as stock, but with the standard ASCII
              characters [, \, ], and ^ in the positions where most Model  I's
              had directional arrows.  This was the default programming in the
              Motorola character generator ROM that Radio Shack  used,  and  a
              few   early  machines  were  actually  shipped  with  this  ROM.
              Finally, german or genie gives an approximate emulation  of  the
              GENIE,  a  German  Model I clone.  Characters are 8 pixels wide,
              and double width is supported even though later GENIE models did
              not include it.

              In  Model  III,  4,  and  4P  modes,  three  sets are available:
              katakana (the default for Model III) is the original  Model  III
              set with Japanese Katakana characters in the alternate character
              positions. This set was also used in early Model 4's.   interna-
              tional  (the  default for Model 4 and 4P) is a later Model 4 set
              with accented Roman letters in the alternate positions.  bold is
              a  bold  set  from  a character generator ROM found in one Model
              III, origin uncertain.

       -usefont
              Use X fonts instead of the built-in character bitmaps.

       -nofont
              Use the built-in character bitmaps, not a X font.  This  is  the
              default.

       -font fontname
              If  -usefont  is also given, use the specified X font for normal
              width characters.  The default uses a common X fixed-width font:
              "-misc-fixed-medium-r-normal--20-200-75-75-*-100-iso8859-1".

       -widefont fontname
              If  -usefont  is also given, use the specified X font for double
              width characters.  The default uses a common X fixed-width font,
              scaled     to     double    width:    "-misc-fixed-medium-r-nor-
              mal--20-200-75-75-*-200-iso8859-1".

       -nomicrolabs
              In Model I mode, emulate the HRG1B 384x192 hi-res graphics card.
              In  Model  III  mode or Model 4/4P mode, emulate the Radio Shack
              hi-res card.  This is now the default.

       -microlabs
              In Model III or 4/4P mode, emulate the Micro Labs  Grafyx  Solu-
              tion  hi-res  graphics  card.  Note that the Model III and Model
              4/4P cards from Micro Labs are very different from one  another.

       -debug Enter zbx, the z80 debugger.

       -romfile filename
       -romfile3 filename3
       -romfile4p filename4p
              Use  the romfile specified by filename in Model I mode, the rom-
              file specified by filename3 in Model III and Model  4  mode,  or
              the  romfile specified by filename4p in Model 4P mode, A romfile
              can be either a raw binary dump, Intel hex format, or TRS-80 cmd
              format (for example, a MODELA/III file).  If you do not set this
              option or the corresponding X resource, a default established at
              compile  time  is used (if any); see Makefile.local for instruc-
              tions on compiling in default romfiles or default romfile names.

       -model m
              Specifies  which TRS-80 model to emulate.  Values accepted are 1
              or I (Model I), 3 or III (Model III), 4 or IV (Model 4), and  4P
              or IVP (Model 4P).  Model I is the default.

       -delay d
              A  crude speed control.  After each Z-80 instruction, xtrs busy-
              waits for d iterations around an empty loop.  A really  smart  C
              optimizer might delete this loop entirely, so it's possible that
              this option won't work if you compile  xtrs  with  too  high  an
              optimization level.  The default delay is 0.

       -autodelay
              Dynamically  adjusts  the value of -delay to run instructions at
              roughly the same rate as a real machine.  The tracking  is  only
              approximate, but it can be useful for running games.

       -noautodelay
              Turn off -autodelay. This is the default.

       -keystretch cycles
              Fine-tune  the  keyboard  behavior.   To prevent keystrokes from
              being lost, xtrs "stretches" the intervals between  key  transi-
              tions,  so that the Z-80 program has time to see each transition
              before the next one occurs.  Whenever the Z-80 program reads the
              keyboard  matrix  and  sees  an emulated key go up or down, xtrs
              waits cycles Z-80 clock cycles (T-states) before it  allows  the
              program to see another key transition.  Key transitions that are
              received during the waiting period or when the Z-80  program  is
              not  reading  the  keyboard  are  held  in a queue.  The default
              stretch value is 4000 cycles; it should seldom if ever be neces-
              sary to change it.

       -shiftbracket
              Emulate [, \, ], ^, and   as shifted keys, and {, |, }, and ~ as
              unshifted.  This is the default in Model 4 and 4P modes, and  it
              works  well with the keyboard driver in Model 4 TRSDOS/LS-DOS 6.

       -noshiftbracket
              Emulate [, \, ], ^, and   as unshifted keys, and {, |, }, and  ~
              as  shifted.   This is the default in Model I and III modes, and
              it works well with many TRS-80 keyboard drivers.  With some key-
              board drivers these keys do not work at all, however.

       -diskdir dir
              Specify  the  directory  containing floppy and hard disk images.
              If the value starts with "~/" (or is just "~"), it  is  relative
              to your home directory.  The default value is ".".

       -doubler type
              Specify  what type of double density adaptor to emulate (Model I
              mode only).  The type may  be  percom,  radioshack  (or  tandy),
              both,  or  none.  The  type may be abbreviated to one character.
              The default is both, which causes  the  double  density  adaptor
              emulation  to respond to the special commands of both the Percom
              and Radio Shack cards.

       -doublestep
              Make all real floppy  drives  double-step,  allowing  access  to
              35-track  or  40-track  media in an 80-track drive.  Linux only.
              See the Floppy Disks section for limitations.

       -nodoublestep
              Turn off double-step mode for all  real  floppy  drives.   Linux
              only.  This is the default.

       -stepmap s0,s1,s2,s3,s4,s5,s6,s7
              Selectively  set  double-step  mode  for  individual real floppy
              drives.  If sU is 2 and diskM-U is a real drive, the drive  will
              be  double-stepped;  if sU is 1, it will be single-stepped.  You
              can omit values from the end of the list; those drives will  get
              the default value set by -doublestep or -nodoublestep.

       -sizemap z0,z1,z2,z3,z4,z5,z6,z7
              Selectively set whether drives are emulated as 5-inch or 8-inch;
              see the section "Emulated 8-inch floppy disks" above.  If zU  is
              5,  the  drive  will appear to Z-80 software as 5-inch; if 8, as
              8-inch.  The default setting (as reflected in the  documentation
              above)  is 5,5,5,5,8,8,8,8.  You can omit values from the end of
              the list; those drives will get the default values.  Setting one
              or  more  of  the  first four drives to 8-inch may be useful for
              CP/M software that supports 8-inch drives.   You  can  also  use
              XTRS8/DCT  with  8-inch drives in the first four positions; even
              though the prompt suggests the unit number must be 4-7,  numbers
              0-3  are  accepted. XTRS8 does not check whether the unit you've
              selected is really being emulated as an 8-inch  drive,  however;
              you'll simply get errors during FORMAT if you get this wrong.

       -truedam
              Turn  off the single density data address mark remapping kludges
              described in the "Emulated floppy disks" and "Real floppy disks"
              sections above.  With this option given, the distinction between
              F8 and FA data address marks is strictly observed on both  writ-
              ing  and reading.  This option is probably not useful unless you
              need to deal with Model I disks that use the distinction as part
              of  a copy-protection scheme.  See also "Common File Formats for
              Emulated TRS-80  Floppy  Disks",  available  at  http://www.tim-
              mann.org/trs80/dskspec.html.

       -notruedam
              The opposite of -truedam.  This setting is the default.

       -samplerate rate
              Set  the sample rate for new cassette wav files, direct cassette
              I/O to the sound card, and game sound output to the sound  card.
              Existing wav files will be read or modified using their original
              sample rate regardless of this flag.  The default is 44,100  Hz.
              See also the cassette(1) man page.

       -serial ttyname
              Set  the  tty  device  to be used for I/O to the TRS-80's serial
              port.  The default is /dev/ttyS0 on Linux, /dev/tty00  on  other
              versions  of  Unix.   Setting  the name to be empty (-serial "")
              emulates having no serial port.

       -switches value
              Set the sense switches on the Model I serial  port  card.   This
              option  is  meaningful  only  in Model I mode, and only when the
              -serial option is not set to "".  The  default  value  is  0x6f,
              which  Radio  Shack  software  conventionally interprets as 9600
              bps, 8 bits/word, no parity, 1 stop bit.

       -emtsafe
              Disable emulator traps (see "Data import and export") that could
              write  to  host  files  other  than  disk images in the original
              diskdir.

       -noemtsafe
              The opposite of -emtsafe.  This setting is the default.

Additional resources
       There are many other TRS-80 resources available on the  Web,  including
       shareware and freeware emulators that run under MSDOS and other operat-
       ing systems, software for converting TRS-80 physical media to the  emu-
       lator's  disk  file  format,  ROM  images, and TRS-80 software that has
       already   been   converted.    For   pointers,   see    http://www.tim-
       mann.org/trs80.html.

Bugs and limitations
       The  emulated  serial  port's  modem status and control signals are not
       tied to the signals on the real serial port, because the  real  signals
       are  not  available  to software through the Unix tty device interface.
       The ability to check  for  parity,  framing,  and  overrun  errors  and
       receive  an  interrupt  when one occurs is not emulated.  Unix does not
       support 2000, 3600, or 7200  baud,  so  these  TRS-80  data  rates  are
       remapped to 38400, 57600, and 115200 baud respectively.

       A  better  signal  processing  algorithm might help read real cassettes
       more reliably, especially at 1500bps.

       Some features of the floppy disk controller are not currently emulated:
       Force  Interrupt  with condition bits 0x01, 0x02, or 0x04 is not imple-
       mented. Read Track is implemented only for DMK emulated  floppies.  The
       multiple-sector  flags in Read and Write are not implemented.  The tim-
       ing of returned sectors is emulated only for the Read Address  command,
       and  not  very  accurately for JV1 or JV3.  If a disk has more than one
       sector with the same number on a track, xtrs will always see the  first
       (counting  from the index hole) when reading or writing; a real machine
       would see the next one to come under the head depending on the  current
       rotational position of the disk.  Partially reformatting a track (which
       TRS-80 programs like HyperZap and Model I Super Utility do  to  achieve
       mixed  density)  is  supported  for DMK but not JV3; however, switching
       densities while formatting (which Model III and  4  Super  Utility  do)
       works on both DMK and JV3.

       Real physical floppy disks are supported only under Linux, because Unix
       does not define a portable interface to the low-level floppy controller
       functionality  that  xtrs needs.  There are some limitations even under
       Linux: Index holes are faked, not detected on the real  disk,  and  the
       timing  of returned sectors is not emulated at all.  Due to the limita-
       tions of PC-style floppy disk controllers, when formatting  a  physical
       floppy  under  xtrs,  you  cannot mix sectors of different sizes on the
       same track, switch densities in the middle of a track, or reformat only
       part of a track.  However, xtrs can read and write to physical floppies
       that have already been formatted in  these  ways  (perhaps  by  a  real
       TRS-80).

       The extended JV3 limit of 5802 sectors is somewhat arbitrary.  It could
       be raised by generalizing the code to permit more than  two  blocks  of
       2901,  but  this  does  not  seem  too useful.  5802 sectors is already
       enough for a 3.5-inch HD (1.44MB) floppy, which the TRS-80 didn't  sup-
       port  anyway.  If you need more space, use emulated hard drives instead
       of emulated floppies with huge numbers of tracks.

       XTRSHARD/DCT ignores the internal write-protected flag  in  hard  drive
       images, but a hard drive image can still be effectively write protected
       by turning off its Unix write permission bits.

       The emulator uses a heuristic to decide what format a ROM file  is  in.
       If  a  raw  binary ROM image starts with 0x01, 0x05, or 0x22, it can be
       misidentified as being in a different format.  This is rather  unlikely
       to occur, as ROMs typically begin with 0xF3, the DI instruction.

       The  joystick emulation could be made to work with real joysticks using
       the X input extension, but this is not implemented yet.

       If you discover other bugs, write fixes for any of these, or  make  any
       other  enhancements,  please let us know so that we can incorporate the
       changes into future releases.

Authors and acknowledgements
       xtrs 1.0 was written by David Gingold and  Alec  Wolman.   The  current
       version  was revised and much extended by Timothy Mann (see http://tim-
       mann.org/).  See README and README.tpm for additional  notes  from  the
       authors.

       We  also  thank  the  following people for their help.  The JV1 and JV3
       floppy disk file formats were designed by Jeff Vavasour, originally for
       his MSDOS-based TRS-80 emulators.  The DMK format was designed by David
       Keil for his MSDOS-based TRS-80 emulator.  The hard  disk  file  format
       was  designed by Matthew Reed for his MSDOS-based TRS-80 emulators.  Al
       Petrofsky and Todd P. Cromwell III supplied font data.  Roland  Gerlach
       contributed  the CP/M import and export programs as well as several bug
       reports and fixes for the emulator itself.  Ulrich  Mueller  added  the
       -borderwidth  option,  improved  the  -scale option and the bitmap font
       scaling, ported the import, export, and settime utilities to Newdos/80,
       and  contributed  the  HRG1B  emulation.  Branden Robinson supplied the
       first version of the cassette man page, fixed Makefile bugs, translated
       cassette to the Bourne shell, and implemented watchpoints in zbx.  Mark
       McDougall provided documentation for the  Micro  Labs  Grafyx  Solution
       card.   Jenz  Guenther  added the -title option and contributed code to
       emulate the GENIE (German Model I  clone).   Joe  Peterson  contributed
       code to emulate the TimeDate80 and the -emtsafe feature.  Denis Leconte
       contributed part of the -scale implementation.

                                                                       xtrs(1)
