View Full Version : Using P28 to P31

12-26-2009, 08:43 AM
Merry Chritmas all,

As I'm new to the propeller, I thought I'd ask before I do something wrong and trash something.

I need to use all 32 IO pins, with the last 2 as inputs, all others outs.

The book says that all the IO's are available for use after bootup. ....· It doesn't say one way or the other about having additional circuitry on P28 - P31 and how that might affect bootup/programming

My question is:·· "Does the eeprom stay connected to 28 and 29 without any affect on IO use of the pin after bootup" ?·

and part 2 is:· "Can the Prop Plug stay plugged in after bootup or downloading a program·without affecting the use of 30 and 31 being used with 10k pullups and buttons for inputs" ?

Thanks in advance,


Peter Jakacki
12-26-2009, 09:34 AM
There are no problems with outputs but bearing in mind that junk will appear on P28..31 during boot. As for the two inputs I would put these on P28 & P30 with appropriate isolation resistors. These pins are normally outputs so no conflict is possible if your inputs are coupled through resistors.


12-26-2009, 02:11 PM
geekgirl: A lot depends on what you are attaching to those 4 pins. I use them on my designs for other purposes.

The propplug is protected by series resistors, so you could place switches on those lines with 150R series resistors as well. Then if a port is an output, no damage will result if the switch is pressed simultaneously.

Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade (http://forums.parallax.com/showthread.php?p=786418),·RamBlade (http://forums.parallax.com/showthread.php?p=849265),·SixBlade (http://forums.parallax.com/showthread.php?p=780033), website (http://bluemagic.biz/cluso.htm)
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator) (http://forums.parallax.com/showthread.php?p=790917)
· Prop Tools under Development or Completed (Index) (http://forums.parallax.com/showthread.php?p=753439)
· Emulators: CPUs Z80 etc; Micros Altair etc;· Terminals·VT100 etc; (Index) (http://forums.parallax.com/showthread.php?p=778427) ZiCog (Z80) (http://forums.parallax.com/showthread.php?p=788511) , MoCog (6809) (http://forums.parallax.com/showthread.php?p=811043)
· Search the Propeller forums (http://search.parallax.com/search?site=parallax&client=parallax&output=xml_no_dtd&proxystylesheet=parallax&proxycustom=<HOME/>&ie=&oe=&lr=)·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz (http://www.bluemagic.biz)·· MultiBladeProp is: www.bluemagic.biz/cluso.htm (http://www.bluemagic.biz/cluso.htm)

12-26-2009, 04:46 PM
Are you certain that you need all those outputs?

Sometimes, a little shift-register goes a long way...


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