I am noticing that when I use VISA write to write a new byte to a parallel point, the signal on lines that were high flash to 0V in the writing process even if the new byte should keep that line at 5V. So it seems that all data pins briefly flash to 0V whenever VISA write is used to write to the port.
This is problematic for applications where I need a stable signal on some lines while pulsing others. For example, I'm attempting to use this to control a stepper motor and it is difficult to generate stable enable and direction signals while pulsing the step signal. I have resorted to conditioning those signals on the hardware side as a (hopefully temporary) fix.
Can anyone give me any insight as to how this problem might be addressed/the source of the issue? It does not seem like it is a problem instrinsic to parallel ports as there is dedicated commercial software that will control stepper motors via parallel ports without this issue. Is it a peculiarity with the VISA Write VI? Or perhaps the drivers for my particular PCI parallel port adaptor?
Thanks!
