I’m no assembly expert, but at first glance at seeing the code, it seems
odd to me that you’re allowing BANK0 to equal 1 sometimes in the follow
stanza:
LDA BankNumMSG ; read current bank number (ascii)
INR A ; add 1
CPI BANK0+NBANKS ; is it > highest valid bank number?
JC @UpdateBankNum ; BankNum <= highest, jump to commit
MVI A,BANK0 ; BankNum > highest, reset to '0'
@UpdateBankNum:
STA BankNumMSG ; commit new bank number
display (ascii)
If you stay with 0-based counting and NBANKS=4, I believe you can simply AND
0b0011 instead of doing the compare and jump. Something like this:
LDA BankNumMSG ; read current bank number (ascii)
INR A ; add 1
AND NBANKS-1 ; Wrap back to 0 if it is >
highest valid bank number
STA BankNumMSG ; commit new bank number
display (ascii)
Of course, even if I’m right, your original code is more flexible. For
example, my shortcut would break if you wanted to compile for a situation
where NBANKS is not a power of two. (I don’t know anything about RAM100,
but I noticed that the two values for NBANKS mentioned were “2” and “4”).
—b9
On Sat, May 23, 2026 at 3:31 PM Brian K. White <[email protected]> wrote:
>
> I've been working on RAM100.CO to make usable assembly source from a
> disassembly so I can add support for more than 2 banks and maybe port to
> kc85, EU, make a common 100/200 source, etc.
>
> I've gotten the 100 version working and added the support for 4 banks.
> So now for 100 & 102, all 1M of MiniNDP is usable for files.
> (not just 102 because I have an untested dip-40 pcb for 100 & kc85)
> I haven't started on 200 yet.
>
> 2 questions:
>
> Is there a less convoluted way to do the ALT version of this chunk of
> code highlighted below? I feel like there must be a more direct way to
> arrange that loop without a jump at both the beginning and end.
>
> Am I being silly even caring about it?
> Both versions work fine and there's no speed or size problem.
> I've scavenged enough bytes elsewhere that even the larger version
> still comes out actually one byte shorter than the original binary
> before padding just to make the bootstrap basic code with hard-coded top
> & end values for the old binary also work on the new binary.
>
>
> https://github.com/bkw777/NODE_DATAPAC/blob/main/software/RAMDSK/RAM100/4-bank/RAM100.S85#L929-L993
>
> What the chunk does is increment or roll-over 2 values.
>
> display bank number ascii '0' to '3'
> control port number 129 to 141 step 4
>
> One defensible functional difference I just realized is with the alt
> version I could have a hot key or call target for basic to jump directly
> to any arbitrary bank rather than stepping through a loop.
>
> --
> bkw
>
>
