Keys

The following keys on the host keyboard have special meanings to xtrs.

F11 toggles onscreen help on the keyboard mappings.

LeftArrow, Backspace, or Delete is the TRS-80 left arrow key. RightArrow or Tab is the right arrow key. UpArrow is the up arrow key. DownArrow or Linefeed is the down arrow key. Esc or Break is the Break key. Home or Clear is the Clear key. Control is the Model 4 Ctrl key (address bit 7, data bit 2). F12 is equivalent to the shifted down arrow key (used as a control key with some TRS-80 software).

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 equivalent 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 signals a floppy disk change (see Emulated floppy disks, below). F8 exits the program. F9 enters the zbx debugger. F10 is the reset button.

In Model III, 4, and 4P modes, the left and right Shift keys are distinct; 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), as do the ASCII-shifted counterparts of the first four ({, |, }, and ~); see above regarding Delete. 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 reversed from what you expect; if, for instance, you press [ but “{” is displayed instead, see -shiftbracket and -noshiftbracket in 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 (DEL).

On a German keyboard, the ¨ and ß 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 option.

Pressing a key on a PC-style keyboard's numeric keypad with NumLock disengaged emulates the Alpha Products joystick. Keys 2, 4, 6, and 8 (KP_Down, KP_Left, KP_Right, and 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 activating 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 active. If you have this problem, you can use xev(1) to determine the names of the X keysyms generated by your keystroke events. You may need to check or update your XKB configuration. Alternatively, you can use xmodmap(1) to remap your numeric pad.

Emulated cassette

To control the emulated cassette, a file called .cassette.ctl in the current working directory keeps track of what file is currently loaded as the cassette tape and the current position within that file. The cassette(1) shell script provides a way to manipulate this file. You may use this script to load and position cassette tape files. The operation works very much like an actual tape recorder. The cassette man page has more information about the 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 provides 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 (on newer versions of LDOS), or PDUBL or RDUBL (on 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 emulate only one with a command-line option; see Options 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 provide both single and double density.

Four 5¼-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 press F7 (see Keys, above).

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, compatible with Jeff Vavasour's popular freeware Model I emulator for MS-DOS; JV3, a compatible extension of a format first used in Vavasour's commercial 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 signature.

JV1 supports only single-sided, single-density diskettes, 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 an 0xFB (normal) or 0xF8 (deleted) data address mark on any sector. On single-density JV3 disks, the nonstandard data address marks 0xFA and 0xF9 are also available. You cannot format a sector with an incorrect track number or head number. 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, double-sided, double-density (18 sector) 5¼-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 everything 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 Bugs and limitations, 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 0xFA data address mark (DAM) for the directory on single-density disks, while later ones wrote 0xF8 but would accept either upon reading. The change was needed because 0xFA is a nonstandard 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 0xFA and 0xFB (which is used for non-directory sectors) upon reading, and cannot write 0xFA. To deal nicely with this problem, xtrs implements the following kludge. On writing in single density, an 0xF8 data address mark is recorded as 0xFA. On reading with an emulated WD1771 (available in Model I mode only), 0xFA is returned as 0xFA; on reading with a WD179x, 0xFA is returned as 0xF8. 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 (technically, 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 5¼-inch drives, xtrs also emulates four 8-inch floppy drives. There is no widely-accepted standard hardware 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 (1, 3, 4, or 4p) and U is the drive unit number (4, 5, 6, or 7). The only difference between 5¼-inch and 8-inch emulated 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 5¼-inch or 8-inch depending on whether you initially put it into a 5¼-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 5¼-inch emulated 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 5¼-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 utility.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
d
d
,DRIVER="XTRS8",ENABLE)
Enter unit number ([4]-7): 
u
u
u

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 5¼-inch drives. The four 5¼-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 machines with “legacy” (ISA bus) floppy drive support should be able to read and write TRS-80-compatible floppies in this way. Many 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 5¼-inch floppy files (diskM-0 through diskM-3) to a real floppy drive, TRS-80 programs will see it as a 5¼-inch drive, but the actual drive can be either 3½-inch or 5¼-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 3½-inch, 5¼-inch, or 8-inch. A 3½-inch or 5¼-inch drive will be operated in high-density mode, using MFM recording if the TRS-80 is trying to do double density, or 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 5¼-inch HD drive holds exactly the same number of bits per track as an 8-inch drive; a 3½-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 0xFA and 0xF9 data address marks available in single density on a real Model I with the WD1771 controller also need special handling. A ISA-bus 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 machine even if it otherwise supports single density. In particular, Model I TRSDOS 2.3 directory tracks will be unreadable.

2.

On writing in single density, xtrs silently records a 0xF9 or 0xFA DAM as 0xF8.

3.

On reading in single density with an emulated WD1771 (Model I mode only), 0xF8 is returned as 0xFA. If you need more accurate behavior, the -truedam flag will turn on error messages on attempts to write 0xF9 or 0xFA DAMs and will turn off translation of 0xF8 to 0xFA on reading.

Hint: Be sure to set the drive type correctly in your machine's firmware. 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 3½-inch drives spin at 300 rpm. Newer 5¼-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 connecting one to a floppy disk controller designed for ISA-bus machines. Older 5¼-inch drives that cannot do high density (“180kB”, “360kB”, or “720kB” 5¼-inch drives) always spin at 300 rpm. All 8-inch drives spin at 360 rpm. If you plug an 8-inch drive into an ISA-bus floppy disk controller—this requires a 50-pin to 34-pin adaptor cable—tell your firmware that it is a 5¼-inch 1.2MiB 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 emulate the Radio Shack hard drive controller (based on the Western Digital WD1010) and use the native drivers for the original hardware.

Using XTRSHARD/DCT XTRSHARD/DCT 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(1) program to create a blank hard drive (.hdv) file. A typical usage would be mkdisk -h myhd.hdv. See the mkdisk 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 the Model 4P also uses M=4) and U is a unit number in the range 0–7. It looks for these files in the same directory 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 M1FORMAT/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
d
d
,DRIVER="XTRSHARD",ENABLE)
Enter unit number ([0]-7): 
u
u
u
FORMAT 
d 
d 
d 
(DIR=1)
    

Answer the questions asked by FORMAT as you prefer. The DIR=1 parameter 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 different unit number.

The F7 key currently doesn't allow XTRSHARD/DCT disk changes to be recognized, 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 Z80 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 Z80 programs to open, close, read, and write Unix files directly. This support is described further in Data import and export, 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(1) program to create a blank hard drive (.hdv) file. A typical usage would be mkdisk -h myhd.hdv. See the mkdisk 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 in the range 0–3. 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 Z80 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 TRSDOS, 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 lowercase, to compensate for TRS-80 operating systems such as NEWDOS/80 that convert all command-line arguments to uppercase. When using the -l flag, you can put a [ or up-arrow in front of a character to keep it in uppercase. 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 possibly other non-LDOS operating systems. 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 omitted, 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 lowercase. When using the -l flag, you can put a [ or up-arrow in front of a character to keep it in uppercase. 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 possibly other non-LDOS operating systems. 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 omitted, EXPORT uses the TRS-80 filename, but with any “/” changed to “.” to match Unix file extension syntax.

Note: The export of files from xtrs may be prohibited by the -emtsafe flag; see Options, below.

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 current working directory under Unix.

Usage: CD [-l] unixdir

The -l flag converts the Unix directory name to lowercase. When using the -l flag, you can put a [ or up-arrow in front of a character to keep it in uppercase. 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.

Note: The change of xtrs's current working directory may be prohibited by the -emtsafe flag; see Options, below.

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

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 lowercase. When using the -l flag, you can put a [ or up-arrow in front of a character to keep it in uppercase. 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.

Note: The execution of Unix shell commands may be prohibited by the -emtsafe flag; see Options, below.

MOUNT/CMD (or MOUNT6/CMD) is a convenience program that switches emulated floppy disks in the drives.

Usage: MOUNT [-l] unixfile unit-number

The -l flag converts unixfile to lowercase. When using the -l flag, you can put a [ or up-arrow in front of a character to keep it in uppercase. unixfile is any Unix filename; unit-number is a single digit, 0 through 7. The command deletes the file diskM-U (where M is the TRS-80 model and U is the given unit-number) from the disk directory (see the -diskdir option below), replaces it with a symbolic link to the given filename, and signals a disk change (as if F7 had been pressed).

Note: The mounting of a Unix file as a disk image may be prohibited by the -emtsafe flag; see Options, below.

UMOUNT/CMD (or UMOUNT6/CMD) is a convenience program that removes an emulated floppy disk from a drive.

Usage: UMOUNT unit-number

unit-number is a single digit, 0 through 7. The command deletes the file diskM-U (where M is the TRS-80 model and U is the given unit-number) from the disk directory (see the -diskdir option below), and signals a disk change (as if F7 had been pressed).

Note: The unmounting of a Unix file as a disk image by deleting it on the host may be prohibited by the -emtsafe flag; see Options, below.

The emulated floppy cpmutil.dsk contains import and export programs for Montezuma CP/M, written by Roland Gerlach. It was formatted as a “Montezuma 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 tracks, 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 archive) in the xtrs source distribution.

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. All of these files are available in the xtrs source distribution.

Interrupts

The emulator supports only interrupt mode 1 of the Z80. 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 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 a Linux kernel configured with HZ=100, you'd see this pattern: (tick, 30ms, tick, 20ms, ...) instead of a tick 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 machines 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 (OSS) /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 version of Unix, you'll need to define the symbol HAVE_OSS in the source distribution's Makefile 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 operating 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 generate 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 Orchestra-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 hardware (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 implements 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 programs.)

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 under TRSDOS/LS-DOS 6 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 not well-documented what their driver software does since the year 2000. If you have software that works with one of them, please contact the author to report what happens when it is used with xtrs.

Also see SETTIME/CMD in Data import and export, above, for another way to get the correct time into a Z80 operating system running under xtrs.

Note that Model I TRSDOS and VTOS 4.0 have a “year 1988” problem, and LDOS/LS-DOS has a “year 2012” problem; see LDOS and LS-DOS: 2012 and Beyond — Technical information by Matthew Reed.

Joystick

Pressing a key on a PC-keyboard-style numeric keypad with NumLock disengaged emulates the Alpha Products joystick. See Keys, above, for details. The emulated joystick is mapped only at port 0, to avoid conflicts with other devices.

Running games

Some games run rather well under xtrs 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 Software 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.