gnorik@gmail.com wrote:
Hello! It is my pleasure to inform that the beta version of oo2c oberon-2 compiler for nmos6502 published. This version uses cc65 as a portable asebmler You can download it at http://sf.net/projects/nmos6502-oo2c
Thanks for the reference, I bookmarked it!It's been 20 years since I last looked at an Atari 800 schematic, mostly just hacked on the XL series. I seem to recall that the Atari Technical Reference had the schematics for the REV A OS board. The board differed from all later Atari 8 bits in that it used the 6502B with external rather then internal circuitry to get the 6502B to work with a !HALT signal.
The !HALT signal was added because the 6502 design did not lend itself to multiprocessor designs. ANTIC being a video co processor that needed to take over the buss.
As much as I can remember, I think they may have employed a 74LS245 in a similar fashion to isolate the 6502B from the buss. If that is the case it should make it a bit easier for me to tie in the phase 2 clock. If I get really lucky, there may be enough left over logic on the board I can use to get it functional.
Rick