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   UltrascreenNEC 1.7L (C) 1987-2026 Ultrasoft / Daniel Born / Gary Weber
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60-column by 10-line display driver for the NEC PC-8201A / PC-8300, Lite edition

Many thanks goes to Daniel Born and Richard Eckerlin for making this a
reality!

This is the LITE companion to UltrascreenNEC. It renders the very same crisp
60x10 small-font display, but leaves out the full-screen BASIC editor. In its
place is a simple, Model-100-style line editor: you type a line, Backspace rubs
out the character to the left, and ENTER submits it. And just as on the
original Ultrascreen100, the Left-arrow key doubles as Backspace, unlike the
NEC's own ROM, where the Left-arrow moves the cursor instead. The payoff is
size: Lite is roughly 2.9K resident versus about 4.8K for the full editor, so
it hands back nearly 2K more of your RAM.

New in 1.7: safe PC-8300 detection. To serve both machines from one build, this
edition brings in the 8201A-compatible ROM image at install. Earlier releases
did that with an unconditional write to the ROM bank-select port, on the
understanding that the write did nothing on a real PC-8201A. It turns out that
write can hang a real 8201A, so it now checks the ROM first and only switches
banks when it is genuinely running on a PC-8300. The PC-8201A is left
untouched. Both machines are hardware confirmed. See CHANGES.txt for the full
history.

LOADER.BA - Tokenized BASIC loader/relocator for creating USCNLT.CO from
            scratch. This will create USCNLT.CO at whatever base-address
            you wish.

LOADER.DO - Text flavor of the BASIC loader/relocator.

USCNLT.CO - Machine language ready-to-load into your NEC machine. You can
            bypass the loader entirely if you just want the fixed-location
            program, which loads at 59443.

FONT.DO   - Universal font editor. It detects the running Ultrascreen, finds
FONT.BA     its font table, and lets you edit the 60-column small-font glyphs
            in place. FONT.BA is the tokenized version.

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How to install
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There are two ways to install it: an automatic loader that does the work for
you, or a manual load if you'd rather place it yourself.

** The easy way: the loader

The simplest path is UltrascreenNEC Lite's loader, LOADER.BA, which works just
like the original Ultrascreen100 loader on the Model 100. It carries the whole
program inside itself, so LOADER.BA is the only file you need to transfer onto
your PC-8201A or PC-8300.

Load LOADER.BA and run it. It asks:

   Install under address (ENTER=max 62336)

Press ENTER to tuck it up as high as memory allows (recommended), or type an
address if you want it somewhere specific. It relocates UltrascreenNEC Lite to
fit, saves a ready-to-run USCNLT.CO built for that spot, and hands you back to
the main menu. Run that USCNLT.CO and you're straight into 60x10, with no CLEAR
to work out and no address math to get wrong.

** The manual way

If you'd rather use the pre-built USCNLT.CO (it loads at 59443), transfer it
onto your machine, then from BASIC park high memory at the load address so the
resident code has a safe home:

   CLEAR 0,59443

Now load and run USCNLT.CO the way you'd launch any machine-language program
(for example, selecting it from the main menu).

** Either way

Once it's installed you're in 60x10, and TEXT, TELCOM, and BASIC will all be
60 columns by 10 lines. Type SCREEN 0 any time to go back to the normal 40-
column display, and SCREEN 1 to return to 60.

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Using Ultrascreen Lite
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When you enter BASIC, TEXT and TELCOM, it's just active by default in 60x10
mode.

Because this is the Lite edition, BASIC line entry uses a plain single-line
editor instead of the full-screen editor: Backspace and the Left-arrow key
both rub out the character to the left, and ENTER enters the line. INPUT, LINE
INPUT and direct-mode commands all behave the same familiar, Model-100 way.

You can temporarily disable the 60x10 display from BASIC with this command:

   SCREEN 0

That flips your computer back into 40x8 mode, which persists in all three ROM
programs. BASIC, TEXT and TELCOM will run just as they did before. However,
you will know Ultrascreen is still installed and waiting to be reactivated
anytime because you'll see "Basic  Text  Telcom" listed in mixed case in the
main menu. To reactivate your 60x10 mode, go to BASIC and type this command:

   SCREEN 1

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How to uninstall
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From BASIC:

   CLEAR 0,62336

Answer Y to the "REMOVE Ultrascreen? (Y/N)" prompt and UltrascreenNEC Lite
unhooks itself, resets the screen to 40x8, and hands all of its memory back.
Answer N and it stays put. (Under the hood, any CLEAR that would reach up into
UltrascreenNEC Lite's reserved memory triggers the prompt; 62336 simply hands
back the maximum.)

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Gary Weber
email: gary@web8201.com
www.web8201.com
