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5V pins in PIO interface

PIO

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#1 ralphb OFFLINE  

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Posted Sat Dec 1, 2018 10:30 AM

The PIO interface has two pins that carry +5V.  Is there any use for this, in the TI 99 world or beyond?  Centronics doesn't specify those pins, so I'm not sure if they're needed for anything today.



#2 Ksarul OFFLINE  

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Posted Sat Dec 1, 2018 12:11 PM

I think a few cables use the +5V to power some chips and or resistor networks in the cable to make the TI outputs compatible with certain brands of printer. Smith Corona and Okidata immediately come to mind as doing this. . .



#3 Vorticon OFFLINE  

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Posted Sat Dec 1, 2018 10:55 PM

I use them to power up TTL chips on my interface boards :) Very handy!



#4 ralphb OFFLINE  

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Posted Sun Dec 2, 2018 2:34 AM

I see, then I better keep these.  Thanks.



#5 TheBF OFFLINE  

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Posted Tue Dec 4, 2018 5:05 PM

I see, then I better keep these.  Thanks.

 

 

A very important difference is the impedance of the power sources.

Pin 12 with a 10 ohm source, can provide some current for practical uses. If you need 50mA however the voltage will drop to 4.5V

Pin 15 with a 1K ohm source is only useful as a voltage source. Draw 0.05 mA (50uA) and the voltage will drop to 4.5V


Edited by TheBF, Tue Dec 4, 2018 5:05 PM.





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