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Parallel ports and _outb

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Heya, I'm just wondering, if I do an _outb to the parallel port (in Microsoft Visual c++), how long will the data pins stay high for? (assuming I sent a decimal value of 255 to the port) Would they just stay high until I did another _outb? What if I invoked a _inb? Thanks Regards, Matt [edited by - Xtremehobo on April 13, 2004 4:37:04 PM]

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The pin will stay high until you tell it otherwise.

However, none of this will work on NT machines. To be able to interface the port, you will have to go through a driver.

You might also want to know that Windows XP will sometimes clear out data on the port every few minutes, because it does searches for new devices. So even if you do invoke an function like _outb (going through a driver), XP will mess things up for you...

However, you can disable a registry key that will disable the device polling.


DisableWarmPoll = dword value: 00000001


If you want to do this on Windows XP, look into 'giveio.sys'. That gives you access to the parallel port, with only a few limitations.

[edited by - Programmer One on April 13, 2004 5:02:55 PM]

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