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@ -27,10 +27,8 @@ Run `BASIC.SYSTEM` and at the Applesoft BASIC prompt type:
```
BRUN APPLECORN
```
to start the software.
For convenience there is an Applesoft BASIC program called `START` which
can be used to launch Applecorn directly from Bitsy Bye.
to start the software. Alternatively, you can simply select `APPLECORN`
in the ProDOS 2.4.2 Bitsy Bye file browser.
When first started, Applecorn will display a ROM selection menu. Choose
the language ROM you wish to load by pressing the associated number key.
@ -46,6 +44,91 @@ input. You may want to keep Caps Lock enabled most of the time!
32 Kilobytes of space is available for your programs and variables. `PAGE`
is set to `&0E0`.
## 'Applecorn MOS' Features
### Compatible ROMs
- In principle any Acorn language ROM should work.
- Currently I have verified operation with:
- BBC BASIC
- Acornsoft COMAL
- Acornsoft FORTH
- Acornsoft Lisp
- Acornsoft MicroProlog
- Acornsoft BCPL
- I have not yet investigated two-ROM languages such as Logo or
ISO Pascal. It may be possible to support these also.
### Compatible Apple II Systems
The minimum requirement for Applecorn is an Apple II system with 128KB
of memory and a 65C02 processor. This includes the following:
- Apple //e Enhanced (but not the original \]\[e, which has a 6502.)
- Apple //c and //c+
- Apple IIgs
- You must enable the Alt Text Mode CDA!
- ROM1: Only `MODE 1` (40 cols) works
- ROM3: Both `MODE 0` and `MODE 1` work
### Video Modes
Two text video modes are currently supported:
- 80x24 `MODE 0`
- 40x24 `MODE 1`
We plan to support HGR graphics eventually.
### Escape Key
The BBC Micro uses interrupts extensively and the Escape key is handled
asynchronously. The language ROM code simply checks an 'escape flag' in
zero page ($FF) from time to time to detect if Escape has been pressed.
The Apple //e does not use interrupts in its keyboard handling and the basic
machine include no sources of interrupts at all (there is no system timer.)
This prevents Escape from being handled in the same manner.
As a partial workaround, Applecorn checks whether the Escape key is pressed
from time to time when it has control, but there are cases where a program
can run forever without ever making a MOS call. In these cases the only
way to interrupt the program is to press Ctrl-Reset.
### Ctrl-Reset
The Ctrl-Reset key combination is the only asynchronously handled keyboard
event on the Apple //e. Applecorn sets up a reset handler which will restart
the ROM after Ctrl-Reset. Any user program in aux memory will be untouched.
For ROMs such as BASIC or COMAL, the `OLD` command can be used to recover the
program in memory.
### Star Commands
`*QUIT` - Terminate Applecorn and quit to ProDOS. Because the 'BBC Micro'
lives in auxiliary memory, you can usually restart Applecorn by running it
again and recover your program with `OLD`.
`*HELP` - Prints out information similar to the same command on the BBC micro.
Specifically it lists the version of Applecorn MOS and the name of the current
language ROM.
`*CAT` (or `*.`) - Simple listing of the files in the current directory.
`*DIR pathname` - Allows the current directory to be changed to any ProDOS
path. For example `*DIR /H1/APPLECORN`.
`*LOAD filename SSSS` - Load file `filename` into memory at hex address
`SSSS`. If the address `SSSS` is omitted then the file is loaded to the
address stored in its aux filetype.
`*SAVE filename SSSS EEEE` - Save memory from hex address `SSSS` to hex
address `EEEE` into file `filename`. The start address `SSSS` is
recorded in the aux filetype.
`*RUN filename` - Load file `filename` into memory at the address stored
in its aux filetype and jump to to it. This is used for loading and
starting machine code programs.
## How to Build
Applecorn is built natively on the Apple //e using the Merlin 8 assembler
@ -56,10 +139,11 @@ In Merlin-8:
- Press `D` for disk commands and enter the prefix of the build directory:
`PFX /APPLECORN`
- Press `L` to load a file and enter the filename `APPLECORN`.
- Press `E` to enter the editor and issue the following command a the `:`
prompt: `asm`
- Once assembly is complete, press `O` to save the object file and
enter the filename `APPLECORN`.
- Merlin will enter the editor automatically (or press `E`). Issue the
following command a the editor's `:` prompt: `asm`
- Once assembly is complete, enter the command `q` to quit the editor,
then select `O` to save the object file and enter the filename
`APPLECORN`.
- Press `Q` to quit Merlin-8.
## Theory of Operation
@ -226,17 +310,6 @@ AUX BANK:
above. For the aux bank, the LC is always banked in since no Apple monitor
or BASIC ROM routines are called, so this is omitted from the diagram.
## 'Applecorn MOS' Features
- In principle any Acorn language ROM should work.
- Currently I have verified operation with:
- BBC BASIC
- Acornsoft COMAL
- Acornsoft FORTH
- Acornsoft Lisp
- Acornsoft MicroProlog
- Acornsoft BCPL
## Limitations
Applecorn currently has the following limitations:
@ -262,48 +335,5 @@ Applecorn currently has the following limitations:
- The Applecorn MOS command line is currently quite limited. More commands
will be added in due course.
### Escape
The BBC Micro uses interrupts extensively and the Escape key is handled
asynchronously. The language ROM code simply checks an 'escape flag' in
zero page ($FF) from time to time to detect if Escape has been pressed.
The Apple //e does not use interrupts in its keyboard handling and the basic
machine include no sources of interrupts at all (there is no system timer.)
This prevents Escape from being handled in the same manner.
As a partial workaround, Applecorn checks whether the Escape key is pressed
from time to time when it has control, but there are cases where a program
can run forever without ever making a MOS call. In these cases the only
way to interrupt the program is to press Ctrl-Reset.
### Ctrl-Reset
The Ctrl-Reset key combination is the only asynchronously handled keyboard
event on the Apple //e. Applecorn sets up a reset handler which will restart
the ROM after Ctrl-Reset. Any user program in aux memory will be untouched.
For ROMs such as BASIC or COMAL, the `OLD` command can be used to recover the
program in memory.
### Star Commands
`*QUIT` - Terminate Applecorn and quit to ProDOS. Because the 'BBC Micro'
lives in auxiliary memory, you can usually restart Applecorn by running it
again and recover your program with `OLD`.
`*HELP` - Prints out information similar to the same command on the BBC micro.
Specifically it lists the version of Applecorn MOS and the name of the current
language ROM.
`*CAT` (or `*.`) - Simple listing of the files in the current directory.
`*DIR pathname` - Allows the current directory to be changed to any ProDOS
path. For example `*DIR /H1/APPLECORN`.
`*LOAD filename SSSS` - Load file `filename` into memory at hex address
`SSSS`. Be sure to specify the address otherwise it defaults to 0000!
`*SAVE filename SSSS EEEE` - Save memory from hex address `SSSS` to hex
address `EEEE` into file `filename`.