Laser 350/500/700 (Video Technology) emulator

The Laser 350/500/700 is a family of home computers based on the Z80 CPU made by Video Technology in 1985. laser500emu emulates these computers in a web browser.

HOW TO USE

To run the emulator, simply open to the link: nippur72.github.io/laser500emu.

You can also clone the repo and run locally, just open the file index.html.

The emulator is written in JavaScript and runs fine in Chrome and FireFox.

KEYBOARD

Laser native UK/US keyboard is emulated, regardless of the actual keyboard layout.

Special keys:

Pause: Laser's Reset key (it acts like a more powerful CTRL+Break)
Alt+R: alternate for Reset key
Alt+P: power on/off the machine
Home: HOME key
Shift+Home: CLS key (clear screen)
End: DEL LINE key
Del: DEL key
Page Up: GRAPH key
Page Down: mu/£ key
Alt+Cursor Left: rewinds and plays the tape
Alt+Cursor Up: stops the tape
Joystick: numeric keypad; 0 is fire 1, Right Ctrl is fire 2

EMULATION SPEED

If emulation is slower than expected you can check how much CPU load the emulator is consuming. Open the JavaScript console (F12) and type info()

> info()
frame rendering: 2.9 ms, load=14.5 %

Frame rendering should be less than 20 ms which is the PAL framerate it is being emulated.

AUTOSAVE

The machine state will be automatically saved and restored when you close and reopen the browser, taking you back where you left it.

If you want to start from scratch, press ALT+P to simulate power on/off.

LOADING AND SAVING FILES

There are three types of files you can work with:

binary files (.bin), plain files that are loaded in memory as-is
floppy disk images (.nic or .dsk), created with dsk2nic or saved from the emulator
audio files (.wav), tape audio files created on the real hardware

Dragging & dropping a file on the emulator's window causes the file to be loaded.

Binaries are loaded at the standard memory address 0x8995.
Disk images are mounted on the drive #1.
Audio files are played back and loaded from simulated tape (CRUN command is launched automatically). To control playback, use Alt+Left (rewind tape) or Alt+Up/Alt+Down (stop tape).

Once a file is loaded, it's also stored on the browser cache so that you don't have to drag&drop it again; you can use the load() function from the JavaScript console.

These are the commands you can type from the JavaScript console (F12 key):

load("file.bin" [,start]) loads a binary file at the specified address
load("disk.dsk" [,drive]) loads a disk image on the specified drive (1,2)
save("file.bin" [,start, end]) saves a binary file
save("disk.dsk" [,drive]) create a disk image from the specified drive (1,2)
download("file_or_image") gets the file as a browser download
remove("file_or_image") remove file or image from browser's cache
dir() lists files on browser's cache
csave() starts recording to WAV (max 5 minutes); use before typing "CSAVE" on the emulator
cstop() stops recording and downloads in the browser the resulting WAV file. Silence before and after is trimmed out.
pasteBasic(text) paste a string of text (e.g. containing a BASIC program)

OPTIONS

Options can be given in the form of query string commands on the URL of the emulator, e.g. https://nippur72.github.io/laser500emu?scanlines=true&nodisk=true

restore=true restore previous emulator state
load=programName load and run the specified program from the software directory of the emulator GitHub repo. If no relative path is specified, programName will be searched in all subdirectories.
nodisk=true disconnect emulated disk drive interface (default is attached)
notapemonitor=true disables audio playback from tape (tape monitor)
charset=english|german|french modify the hardware switches used to address the charset ROM (default is english).
scanlines=true turn on the scanlines effect (default is off)
saturation=value set color saturation between 0 (B/W) and 1 (full color)
bh=value horizontal border width in pixels (0-40)
bt=value vertical top border height in pixels (0-65)
bb=value vertical bottom border border height in pixels (0-55)
aspect=value aspect ratio (default 1.55)
rgbmaskopacity=value opacity of RGB mask effect (default is 0, no effect)
rgbmasksize=value size in pixel of RGB mask effect (default 3)
keyboard=value use real PC keyboard layout (only keyboard=ITA supported at the moment)

DEBUGGER

You can plug your own Javascript debug functions by defining debugBefore() and debugAfter(elapsed) in the JavaScript console.

debugBefore is executed before any Z80 instruction; debugAfter is executed after the istruction and the number of occurred T-states is passed in the elapsed argument.

Within the debug functions you can access all the emulator variables, most likely you'll want to read the Z80 state with cpu.getState() or the memory content with mem_read() and mem_write().

AUTOLOADING

The emulator can be used in cross-development allowing to automate the process of loading and executing the program being developed. This will save lot of annoying drag&drops.

To enable "autoload":

clone the emulator on your local machine (it won't work in the online-version because of browser restrictions)
in your compile chain (make etc..), copy the binary you want to execute in the emulator directory naming it autoload.bin
execute node makeautoload, this will turn autoload.bin into JavaScript code (autoload.js).
refresh the browser, the program will be loaded in memory and make it RUN

When you no longer want the file to be autoloaded, delete autoload.bin and run again node makeautoload.

EMULATOR FEATURES

accurate to the scanline level (changing video mode will reflect next scanline)
all graphic modes are emulated
sound is accurate but lags due to browser latency
old CRT look (simulated scanlines), 50 fps as in PAL standard
cassette output is redirected to PC speakers (can be recorded and played back on a real machine)
printer is emulated by redirecting it to the JavaScript console (F12 on the browser)
ROM Basic 3.0
Joystick 1 emulated as NUMPAD + RIGHT CTRL (fire1) + NUMPAD0 (fire2)
Floppy Disk Drive NOT emulated (we miss the ROM DOS Basic 1.0, if you have it please contact me)
Keyboard not perfect yet, and with italian layout only
ALT+R or CTRL+BREAK is reset key, ALT+P is power on button
Drag & drop binary files to load them on the emulator
automatically saves the state of the emulator

There are also a bunch of commands that you can run from the JavaScript console (F12) to load or save programs. Saved programs are seen as a downloaded file in the browser.

Programs are also stored on the internal browser storage (HTML5 localStorage), simulating a sort of disk drive.

RESOURCES

The laser500emu repo serves also as a container for Laser 500 software and documentation that I have collected along the way, make sure to have a look at:

Other resources about the Laser 350/500/700 computers are:

Bonstra's GitHub repo laser500-doc by
a dedicated Facebook group
a forum thread on AtariAge.

nippur72 / laser500emu