parallel input using control register

[nightlight]

Hi, all. i have beening trying to use the control register and the status register as parallel port input. i have read the article named "Using the Parallel Port in LabVIEW" at the address "http://zone.ni.com/devzone/conceptd.nsf/webmain/72C6FC6CE4AD4D1386256B1800794596?opendocument"
i did exactly what it told me to do. program the control signals c3,c2,c1,c0 to logical high first(that is 0100 in binary), and then try to read these control signals back. these pins are exteranlly connected to my circuit.

but no matter how i change the external signal level(0 and 1), the values i read in are always the same as the values i write to the control register(0100 in this case), can anyone tell me why? please!!

[Jeremy Braden]

If you are using VISA, you need to short a pin.Why do I Receive Error -1073807253 When Using The Parallel Port with VISA? . This is a very common problem.

I recommend using in port.vi and out port.vi. In LabVIEW 7, they work on NT/2000/XP and you just pass them a memory address and a value to write. Be sure that if you give an address in hex that it is not being interpreted as decimal. This is another common problem.

Be sure to check your bios (the screen that pops up before your OS) to see what mode your port is set to. I recommend spp aka standard parallel port.

[nightlight]

thanks for your reply, but i later found out that it was because the control pins of my computer don't have internal pull up resistors. it worked fine after i added them externally.