Synchronous serial Re: E-Mail Formats RE: Future of cctalk/cctech

Paul Koning paulkoning at
Thu Jun 18 19:25:24 CDT 2020

> On Jun 18, 2020, at 5:55 PM, Peter Coghlan via cctalk <cctalk at> wrote:
> ...
> I can rustle up +/-12V with a bench supply or two but I don't have a
> 1488 handy.  I should be able to borrow a MAX232 from something though.
> I don't have any baud rate generators lying around either.  How about a
> 555 generating square waves round about 10kHz for something approximating
> 9600 bps?  Does it have to be spot on a "valid" rate or will anything
> "close" do as long as it is the same at both ends?
> To be absolutely clear, do I have to drive pins 15 and 17 going to both
> interfaces ie four loads on the driver in total?

Yes.  Both sides are looking for a receive clock to tell them were the incoming bits begin, and a transmit clock to control the shifting out of the transmit bits.

Any speed should work so long as it's slow enough.  So a 555 feeding a MAX232 should be fine.  Most variants of that device have several drivers so you can split the four loads over more than one driver if you want to.  That's probably not necessary.


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