How many bytes is VBIOS again?

... Yup, it's a question of how much customisation you have/need. The original concept here is an absolutely minimal DROM which (a) gets you moving initially and (b) provides an emergency recovery mechanism.

Yes, the "two DROM approaches" are for two different views of, (a) what "getting you ...

... The big catch of course is that it's in no way reprogrammable. ...

Yes, the strategic decision is whether the reprogrammability should be at the DROM level or at the punched in program level, since the punched in program is infinitely reprogrammable, but in a very, very old school style of ...

So that means mini-DROM would be about half of that, and that mega-DROM is a two board enterprise for leaded components and plated through holes?

Bruce, looking at your execute code in V9, I am impressed by the level of sneaky (assuming I understood it correctly).

cmp #KEY_GO
bmi loop_hex ; enter hex value
beq exec ; jump punched in code
...
org $fffc ; +4
dw start
exec:
dw addr0 ; Jump executes BRK which calls addr0


So the BEQ ...

I don't see why not. The reason I'm concerned about is not when it's made with new eeproms - they're delivered unlocked - but to avoid surprises when someone gets a locked second hand part.

A three-pin header would do the job.

Neil

Indeed, given the time investment to get an EEPROM populated by ...

... but the process might be to lift the leg of A14 (pin 1) and attach it to A12 (pin 2) to allow erase, lock, and unlock, and to attach it to GND to use as normal. That would allow normal external programming with no special requirements (except to offset the code to live at $C000) and yet still ...

Are there still four unused /IO selects in $Axxx?

One strategy would seem to be to change /romsel so that a write into one of the free $Axxx /IO ... specifically the one that includes $AAAA ... also triggers /romselect, so that A14 will be low while ROM is selected when writing into that specific ...

n... For example, I think there are nine references to memptr / memptr+1. Just moving that from 08/09 to FE/FF would save soldering 54 diodes.

This is a very different slant on code optimization. Minimizing the number of zeros rather than minimizing the number of bytes. ...

Excellent point ...

...
To avoid confusion (mine) - your most recent post is for a monitor which might for example be keyed in using Paleo, not part of Paleo itself, right? ...

Yes, a micro monitor that can be programmed into the top two pages of an EEPROM, after punching in the EEPROM writing routine and the micro ...

The break point support I've got sketched out relies on storing data in dedicated space high in the zero page, having a function to go to the first byte in that space (rega), and having a return from break function that executes if in break mode, is a dead key if not in break mode:
org $fe70
break ...

Bruce... V8 is one byte too long :(


; then update LED and get key
; +10
ff99 : b9fa00 lda leds,y
ff9c : 990098 sta led_addr,y ; display bit pattern
ff9f : ad0090 lda keypad
; d7=NOR(row1,row2,row3,row4,row5)
ffa2 : 302b bmi loop_99 ; no key pressed

There are eleven bytes here...

Fixed a ...

For the Mesolithic micro-monitor, I've been looking at getting rid of polling for release, which will glitch the LED's. The idea I've been working on is executing the key the first time a key is pressed, and also setting up "key pressed" mode, so until the key pressed state is reset, the key is not ...

... Bruce is going way too fast for me! ...

TBC, I'm moving much faster than I am making progress ... but I did make some actual progress yesterday, so V8 is a good alpha to see whether it assembles in the assembler you use and whether the simulator makes it look like it's not buggy.

Since these ...

I am thinking about giving bitbanging a MAX3100 using the 65C22 a shot to simplify the bus-design, but I figured since I have 4 more 65C22s from my order I could at least give it another shot before giving up on them :) Thanks, then I know that at least in theory they should be able handle higher ...