The PC/XT used a clock/data protocol directly into an interrupt driven shift register which could handle 300 Kb+. The AT is microcoded and uses pseudo-RS-232 format but with the bit windows timing relaxed to allow for for microcoding. The keyboard is dominate but the buss direction can be reversed when the adapter pulls the clock line low and holds it.
Sent from my MetroPCS 4G LTE Android Device -------- Original message --------From: k...@aspodata.se Date: 8/27/17 2:04 PM (GMT-06:00) To: dng@lists.dyne.org Subject: Re: [DNG] serial and ps2 ports. Alessandro: > On Sun, 27 Aug 2017 at 18:03:08 +0100 > Simon Hobson <li...@thehobsons.co.uk> wrote: > [...] > > AFAIK the underlying protocol for the keyboard is the same (or near enough > > for simple conversion) between the two connector formats to allow for easy > > conversion between plugs. > > They are, adaptors are purely mechanical. PC/AT and PS/2 have the same protocol and electrical spec. except they have different connectors. The protocol is bidirectional. PC/XT has the same pinout and connector as PC/AT but not the same protocol and they won't work together. The protocol is keyboard -> pc only. See page 16 of http://kbdbabel.sourceforge.net/doc/kbdbabel-vortrag-vcfe80-20070429.pdf and https://en.wikipedia.org/wiki/IBM_PC_keyboard for details. Regards, /Karl Hammar ----------------------------------------------------------------------- Aspö Data Lilla Aspö 148 S-742 94 Östhammar Sweden +46 173 140 57 _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
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