Re: TI-H: Parallel Port Expander
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Ed Plese, Jr. wrote:
>
> Today I finally got my Parallel Port Expander to work correctly and I
> think consistently. Basically, all it does it receive 8 clocked bits
> from teh link port and output them in parallel format. I'm not going
> to post the schematics yet because I have yet to come up with a way
> to synchronize the circuit with the calculator without having to turn
> off and on the circuit. But it does work, at at very high speeds.
> In normal mode, it transfers 4096 bytes from ROM in a little over 2
> seconds, and in turbo mode, about 1 second. These transfer to about
> 16 Kbps (bits per second) and 32 Kbps, respectively. This is pretty
> close to the maximum transfer rate for the link port, because I don't
> think the software can be optimized much more. But, still this is a
> very high transer rate. With the Serial Flash Expander transfering
> at these speeds, it could copy 28K in either 14 or 7 seconds,
> depending on the mode and also depending on how fast the software is
> and how many address bytes it has to send. But, for those of you
> interested in video playback, this would be either 2 or 4 frames per
> second, which is pretty good for a calculator.
>
> -Ed
I've built one too, with a 74LS164 and some other chips. It was meant to
be a Centronics compatible (not 100% but enough for a printer) 8-bit
bidirectional port. I almost finished the port but then my TI-85 broke
(spilled lemonade on it, couldn't fix it). Now I have the most recent,
untested prototype but haven't tested it, but it might and should work.
If anyone is interested, I might take a look on what I thought up last
spring...I'd still go for an I2C parallel extender now that I know those
exist.
-Ozone
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--
*** Osma Suominen *** <a href="mailto:ozone@clinet.fi">ozone@clinet.fi</a> *** http://www.clinet.fi/~ozone
***
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