Urgently need a copy of Motorola Application Note AN-754 "Device Operation and System Implementation of the Asynchronous Serial Interface Adapter".

I have two boards from college days (1979) one is a MC6809 and the other is a MC6802. Both have terminal access via RS-232 through the ACIA MC6850.

I need sample I/O code to manage bi-directional communication to get the boards up.

  • Google provided nothing but ads. A few snippets. I need a full listin of the I/O code. The App. Note used to be hosted on Bitsavers, but no longer, and not on archive.org Aug 31, 2020 at 16:37
  • Ahhh, yes, the most 'obvious' ones are now dead links.
    – Jon Custer
    Aug 31, 2020 at 16:48
  • Many of us dumped print versions, cause "everything's on the net". Except it no longer is. I still have the Data Books, and ost of the Motorola AN's, but this one seems scarce. I spent the better part of yesterday checking the usual suspects... Aug 31, 2020 at 16:51
  • Agree. And the '754' pulls up way too many IEEE-754 references just to make it harder. I've deleted the original comment since it was not accurate.
    – Jon Custer
    Aug 31, 2020 at 16:57
  • And the Fairchild AN-754 is not the Motorola one...
    – Jon Custer
    Aug 31, 2020 at 17:11

2 Answers 2


The following book at archive.org contains several applications notes. Among those you have AN-754 on pp. 21-32.


While I couldn't find an online copy as well, so I had to check the dead tree issue :) It won't make you happy, as there is no sophisticated example given. Only two rather simple flow diagrams and a dotzend instructions loading the registers. Most text is spend repeating the datasheet.

Then again it shouldn't be a huge task to get a 6850 running. It is a no frills serial port. Everything needed is nicely described in the datasheet. There are no suprises.

There are countless examples out there how to use, like in Leventhal's 6809 Assembly book. Its examples are similar to the ones in the app-note. You might as well want to check the manuals for the boards you have, as Motorola used to provide rather detailed manuals. In fact, Leventhal did as well write books for some Motorola boards, like Experimentation with the Motorola MEK 6800D2, which goes into greater detail than the app-note.

Of course, if your problem is more exotic than straight serial communication, why not post a question about?

  • Okay, I now have the Datasheet and AN-754, as well as some sample code. Thanks to everyone for the quik response! And no, Raffzahn, not exotic. I'm just returning to this after 35 years at the Enterprise Architecture level, so much has been lost on the fog of war... Aug 31, 2020 at 19:22

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