[Coco] 6820 and 6821 pin compatible?

[jdaggett at gate.net]

Joel

The MC6820/ MC6821/ MC6822 all have the same pinouts. They differ in how the ports are 
constructed. Softwarewise they interface the same to either the MC6800/ MC6802/ MC6809 
processors. 

james 

On 5 Nov 2009 at 21:33, Joel Ewy wrote:

> I'm restoring an SWTPC 6809 computer.  I intend to run OS-9 on it.  I 
> also want to try out FLEX and UNIFLEX (the latter of which I'm sure this 
> computer once ran).
> 
> I've got a timer board, that I believe (judging from the OS-9 
> configuration of the SWTPC emulator) provides the system clock 
> interrupts.  It has a socket that, according to the documentation, once 
> housed a 6820, but now sits empty.  I can probably dig up the 
> documentation, but I bet somebody on this list can tell me without 
> cracking a book or downloading a PDF whether or not I can just plop a 
> much more readily available 6821 in there instead.
> 
> If you're interested in following my progress on this project, I've been 
> blogging about it:  http://8littlebits.wordpress.com/category/swtpc/
> 
> The CoCo gets mentioned as well, and I used a CoCo emulator to make a 
> boot disk image I'll eventually use when I'm ready to try and boot this 
> thing up.
> 
> JCE
> 
> 
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