I'm wondering if there is any interest in having BASIC in ROM allowing turn-key BASIC programming; if so then please read on.
One of my design goals was for my S-100 projects was to get BASIC in ROM running. I wanted to do this for several reasons:
- It takes me back to the days of my Radio Shack Model I with BASIC in ROM
- I find BASIC really useful for debugging boards; PEEK, POKE, INP, OUT and WAIT are really useful
- BASIC gives me a turn key solution; turn the power on and I have the BASIC prompt
- For quick and dirty code I find BASIC easier to use / manage
The chosen BASIC:
I looked at the source for several BASIC interpreters and finally settled on using the NASCOM BASIC that had been ported to the "Space Time Productions" SBC. Joel Owens (http://www.joelowens.org/z80/index.html) had ported it, converted it to Console I/O, documented it and provided clean commented source on his web site. Joel gave me the go ahead to use the source for this project.
What I did:
- One of my design goals was to use common tools to manage the code; NOTEPAD++.EXE as the editor and TASM as the assembler. I wanted to code to be compiled on a PC then using a USB EPROM programmer to program the EPROM.
- I formatted the code so it looks clean using NOTEPAD++.EXE
- I added code to allow it to use 16550 UARTS; this was tested using the UART on the prototype S-100 Utility (MSX2) Board.
- I added code to allow it to use the USB serial adapter on the S-100 Serial IO Version 02 board.
- The original code had BASIC at the bottom of MEMORY; I wanted it in high MEMORY instead so that the low memory areas are RAM based to allow CPM to run; I made edits to move it to the $E000-$FFFF address space.
- I modified the CLS command to use ANSI escape sequences to home the cursor and clear the screen.
- I added a HOME command to use ANSI escape sequences to home the cursor.
Revisions:
There are two versions (source branches)
- One meant to run in LOW memory targeting the EPROM socket on the S-100 Utility (MSX2) card (16550 UART).
- One meant to run in HIGH memory on my S-100 Z-80 CPU V2 board - I had to make a minor change on the board to allow a full 8K of EPROM to be used.
BASIC's Features include:
- Floating point maths with a full set of functions
- For, Next, Step, Goto, Gosub, Return, Stop, On, Wait, End
- PEEK, POKE, INP, OUT, HEX
- String functions MID$, RIGHT$, LEFT$, LEN, STR$, VAL, ASC, CHR$
- USR function
- AND OR NOT
- DATA READ RESTORE INPUT
- UPPER and LOWER case
- Fully tokenized BASIC
- Auto detection of MEMORY size
Games:
- I've updated STAR TREK to run
- I've updated HUNT THE WUMPUS to run
Still to do:
- Fully test it
- Add drivers for other Serial IO devices such as the Z-80 DART
- Clean up the build environment - currently it's just a BAT file
- Clean up the source so there is only one source code file that used #DEFINES to control how it's compiled
- Update the BASIC documentation
- Have more fun
-Neil