Shell bottom: No photoScreenshoots: No photoExtra info:
Thanks to zxdragon photos I was able to rev-en this PCB. Surprisingly I was almost 100% accurate with my guesses, here are differences:
* CHR-ROM order is 100069C + 100068C, not vice versa
* MJ338986 is 74191 with CLK and /CNTEN pins swapped (pin4=CLK, pin14=/CNTEN)
* $600A.0 must be written with 0 to acknowledge IRQ
* counter's CLK = (not $600A.0 OR M2), /CNTEN = GND (but the behaviour is exactly the same, just the fourth OR gate is wasted that way)
[url=https://obrazki.elektroda.pl/6558169000_1572031817.png][img]https://obrazki.elektroda.pl/6558169000_1572031817_thumb.jpg[/img][/url] [url=https://obrazki.elektroda.pl/7771482100_1572031868.jpg][img]https://obrazki.elektroda.pl/7771482100_1572031868_thumb.jpg[/img][/url] [url=https://obrazki.elektroda.pl/1972562000_1572031870.jpg][img]https://obrazki.elektroda.pl/1972562000_1572031870_thumb.jpg[/img][/url]
Comments:
fcfuck:
2023-01-12 04:08:22
这个与原版比99.9%的精确
This is 99.9% more accurate than the original