Changes
F9E1h (or F9E3h) Schneiderware V/24 8251 USART chip Control
Clock source comes from a [[8253 chip]].
Clock input to that chip is jumper-selectable: 2MHz (default), or 1MHz. Caution: The RTS/CTS and DSR/DTR handshaking signals are disabled by default (via jumpers) (and, in worst case, also by additional inaccesible hardwired connections, hidden underneath of the jumpers)
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The original '''8251''' seems to be very rare (there's no programming info found in the internet). The '''8251A''' is backwards compatible, but includes some additional features. The 8251A gives some details on the additional features, so one could eventually use the '''8251A''' datasheet to reconstruct the functionality of the original '''8251'''.
However, since the 8251 is so rare, it's rather doubtworthy doubtful that the Aleste or Circit actually uses that these chips, they probably they use 8251A chips.
* The Circit advert says 8251 (which is maybe meant to be an abbreviation for 8251A).
* [[Media:8251A.pdf]] - newer 8251A datasheet (detailed info)
* [[Media:8251.pdf]] - older 8251 datasheet (pin-outs out only, without programming info) [[Category:Electronic Component]]
