I found that Zilog has taken down the datasheets for their old products. Further, though I found the pinout of the various versions of the SIO, I found no data sheet at Thomas Scherrer's Z80 Family Support page. Google search on "Z80 SIO" yielded nothing useful. Since these parts have been out of use for well over ten years, it's no surprise that the reference materials are getting scarce. Maybe we should find a place to put the complete documents, since Thomas Scherrer's Z80 Family Support page only has the pinout. Keep in mind, by the way, that there are actually four parts that fall under the umberella of "Z80 SIO" and these include the DART. The SIO/0 and DART share the same pinout/bondout, but the synchronous clocking logic in the DART is not necessarily functional. The SIO/1 and SIO/2, though similar, are bonded out differently, as reflected in Thomas Scherrer's Z80 Family Support page though that doesn't tell you about the programming. Looking at the signals that are internally tied together will shed some light on the differring programming considerations, though the pinout doesn't tell you everything. I believe I still have the full-size data sheets from Zilog. Those will probably provide the best scans if nobody else has them. The data books are only half that size. Unfortunately, the later data sheets are only about half-size as well. I found that no problem back in '76 or so, but nowadays, reading the databook is always preceeded by an easter-egg-hunt for the reading glasses. If you're really desperate for a scan of the sheet, i.e. you need it NOW, then email me and I'll see if I can get it done right away. (I'm in scanning mode for the morning.) Dick ----- Original Message ----- From: "Neil Cherry" <ncherry(a)home.net> To: <classiccmp(a)classiccmp.org> Sent: Friday, December 15, 2000 8:31 AM Subject: Re: Z80 SIO programming