Apple ][+ v0.10
===============

History
=======

v0.10 Initial release
      Applesoft BASIC ROM runs

About
=====

This RBF file emulates the Apple ][+ on the Altium NanoBoard.

You will need a VGA monitor and a PS/2 keyboard plugged into the
"PS2 KB" connector on the NanoBoard.

Keyboard Mapping
================
Most of the Apple keyboard maps directly to the keys on the PS/2 keyboard.
The <RESET> key is mapped to the Nanoboard RESET pushbutton.
<CAPS> is currently not implemented.
<CTRL>+<SHIFT> key codes are currently not implemented.

Dipswitch Settings
==================
The DIPSWITCHES currently control the foreground and background colour
of the Apple display - a legacy of the TRS-80 emulator. It's a bit confusing
because it affects the text and graphics modes of the display differently.
It's currently WIP... I suggest you use 10101111 for a green-on-black display.


*SPECIAL NOTES*
===============

Note that this RBF file contains the copyrighted Apple ][+ ROM images. 
Please use discretion when distributing this file.

Implementation is *very* preliminary. 

Currently implemented is:

* RAM $0000-$7FFF (32KB)
* Text RAM $0400-$07FF
* Hires Page 1 RAM $2000-$3FFF
* Full inverse/flashing character set
* Soft-switch bits for rudimentary text/graphics control. Not all combinations
  are implemented and mixed mode is a hybrid hires graphics overlaid on text.
* 1-bit sound (speaker)

This is sufficient to boot Applesoft BASIC and write a simple hires program
using 'HGR'.

Notes on text/hires implementation
----------------------------------

Apple text characters are 7 pixels wide. Due to a limitation of the current
PACE tilemap engine, the characters are displayed as 8 bits wide - the 1st
pixel of each text character has been blanked out in the character ROM.

Apple hires graphics use only 7 bits of each byte for pixel data. The 8th bit
has special functionality (not yet implemented). Due to a limitation of the
current PACE bitmap engine, all eight bits are displayed as pixels. This will
distort the screen slightly and introduce missing/extraneous pixels in every
eighth column of the hires display.

A 'hybrid' mixed text/graphics mode which overlays hires graphics over text
was not available on the Apple. This mode should display only the last 4 lines
of text with a truncated hires page.

T.B.D.
------

* Add secondary text, graphics pages and implement Lores graphics.

* Fixed text, graphics modes to remove non-displayed 8th bit in each byte.

* Implement full 'Soft-switch' functionality including full complement of
  video modes correctly.

* Add full 64K and possibly 2nd bank of 64K RAM.

* Emulate the floppy controller/drive. Initially I'll look at emulating a disk
  using either the SRAM or external EPROM. Then I'll interface a PC floppy disk
  to the NanoBoard to boot off a 3.5" disk. Other options include interfacing
  via a USB device (GUPPY) to read virtual disk images from the PC.
  
* Emulate the cassette interface. This could be done over serial/USB/other from
  the PC to allow virtual cassette images to be downloaded.
  
* Complete the whole family of Apple II emulations!

Contact
=======
<msmcdoug@optushome.com.au>