I am building my own 6502 based microcomputer. I am going tu put EhBasic on its EPROM.
At this point everything works. Of course I still need add load/save subroutines and as my assembly programming skill grew, I will try to add additional features (like additional commands for RTC usage).
At this point I'd like to set fixed memory size, to do not have to set it after reset. How could it be done?

My memory map:
32kB of RAM
8kB window for four RAM memory banks.
8kB memory space for I/O
16kB of EPROM

What memory size should I set? Full 32kB? 32kB minus zero page and stack?

ehBasic traditionally probes RAM to find the top, but if you are using a 65C02 (WDC), then it's very worthwhile looking at the variant put together by floobydust here: viewtopic.php?f=5&t=5760

There are 2 simple variables to set for Ram_base and Ram_top - so in my 65C02 system, I set Base to $0E00 and Top to $8000 to fit into a 32K RAM, with the ehbasic code assembled to start at $8000, so you can adjust to suit.

-Gordon

_________________
--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

Ok, now I see that if I simply press an enter without supplying value, it simply assume default value.
If there is a way to permanently disable this question?

You have the source ... make the edit.

-Gordon

_________________
--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

If you grab my version referenced above, there’s no prompt to worry about. Just set your base and top addresses and you’re done. Also, latest version has an improved RAM test plus Load and Save vectors with some useful code... just implement Xmodem for transfer and you’re done.

_________________
Regards, KM
https://github.com/floobydust

I have to admit that I am a little bit confused... This version is a little bit different from standard 2.22, which I used in my project.
1) There is no min_mon.asm file, so where to look for low level I/O subroutines? I thought they were transferred to the main basic.asm file, but there are no ACIAout and ACIAin subroutines. Were they renamed?
2) I see it doesn't assemble with acme asembler...

Maybe you could simply point me to the fragments of code responsible for skipping memory size prompt and Xmodem load/save functions? This way I could include them into my own project...

So, here's some detail:

1- I use the WDC Assembler/Linker package, so the source has been reformatted and much cleaned up. Note that the WDC Tools are free.

2- It's now a single source file, there is NO minimal monitor code, it relies on your SBC having a BIOS for your hardware that provides at least two basic functions:
a- Get a character
b- Send a character

3- All of the vectors are soft-loaded into Page 4 ($0400) as is the input buffer. In the source file, these vectors are declared starting at line 7523. The BIOS routines (from my SBC) are shown starting at line 7548, i.e., $FF36 is get a keystroke, $FF3C is send a character to the console.

4- Memory test, show and go starts at line 527. It's fairly simple, loads/tests for $55, $AA and $00 starting at Ram_base to Ram_top.

5- Xmodem code pieces still rely on my C02 Monitor for the core Xmodem-CRC transfer. The code in the basic source file handles specifics for EhBasic, then call the monitor routines. The Xmodem code in the basic source starts at line 7514.

6- Cold and Warm start are handled by the Monitor... which simply prompts the used for Cold or Warm, then Jumps to the Basic code. Cold start is at $B000, which is start of the code assembly. Warm start is $0000, which requires that basic was Cold started earlier, else you just jump to whatever is loaded at $0000.

My updated code has all of Klaus' fixes and numerous enhancements along with a consolidated page zero usage, plus it requires less page zero use as the Chrget/Chrgot equivalent code (LAB_IGBY) is maintained in ROM and only the 2-byte pointer is maintained in page zero.

If you can provide some details for your SBC hardware, perhaps I can provide you a simple BIOS that will work. My current C02 Pocket SBC uses an older Philips/NXP SCC2691 UART and one of my older SBCs uses a common 6551 ACIA. I have full-duplex interrupt-driven and buffered BIOS code to run either chip as a console.

I'll be posting an updated BIOS/Monitor for my current C02 Pocket SBC shortly. The BIOS (and hardware page) take less than 1KB and the Monitor just a tad less than 5KB and is quite rich in function. It also requires the WDC Tools package to assemble and link.

Hope this helps....

_________________
Regards, KM
https://github.com/floobydust

I maintain a parallel fork of EhBasic where almost everything that is specific to a particular target is stripped out and placed in a separate monXXX.asm file, so to target a different platform you can leave the Basic interpreter code untouched and simply write a new monXXX.asm file. I've just updated it with the latest v2.22p4 updates.

For the OP's original question, copy one of the monXXX.asm files and update it. From what you posted I'm guessing:

$0000-$7FFF 32kB of RAM, $00xx=zero page, $01xx=stack, $0200 upwards: fully free
$8000-$9FFF 8kB window for four RAM memory banks.
$A000-$BFFF 8kB memory space for I/O
$C000-$FFFF 16kB of EPROM

So:

Then update MON_INIT for any target-specific initialisation you need to do, and write routines for your target to do Check for keypress, Character output, program load, and program save.

If you want the system to supply the memory size instead of asking the user, use:
and have a routine in the monXXX.asm file MON_LIMITS that sets the memory size, eg:

_________________
--
JGH - http://mdfs.net