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SIO for Z800?


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It'd be Atari's never released Z800. The Zilog was scheduled for release in 1985. Likely that SIO document was made during development of the 800 so probably 1978 or 79.


While having a look, noticed the Wikipedia page on Atari SIO isn't very good, makes such notable mistakes as calling SERIN and SEROUT shadow registers when they're not.


Atari SIO could probably be made to work with various other system's peripherals though the constraints without extra chip hardware are the 0/5V logic level and fact that the bitstream is always bracketed by start/stop bits, lsb first and 8 bits no parity.

Bitbanging could be used in theory but you lose some flexibility doing it that way.


I've been meaning to try and get the Atari to talk to a 1541 but have lack of knowledge of the C= protocols which has been a holdback factor.

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There's no reason Z80 stuff can*t do SIO. In fact, I ran SIO2CP/M on a TeleVideo system with Z80SIO and CTC chips. I even had UltraSpeed working.


I then ran it on a CP/M emulator on an MS-DOS machine and that worked as well.


Various Atari compatible peripherals use different families of chips. Even some manufacturers (Rana) changed their chipsets.


All you need is a serial port and at least one programmable lo/hi pin for Command.

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So long as either there's hardware IO capable or CPU fast enough to bit-bang then most old systems could probably use SIO devices.


Re my project, probably a better starting point might be to get a C64 doing SIO. I already did a 1050 emulator on the ST which was almost all software driven, only used the hardware functionality to derive the 19.2k timing.

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