[Linux-parport] Bidirectional Mode question

[Melvin Alvarado]

Hi, 

I am trying to connect a FPGA with Linux PC through the parallel port.
I set in the BIOS bi-directional mode for the port, and when I used
the instruction PPDATADIR for reverse, the data outputs of the port
were 4.6 V, in this moment the FPGA tried to write a low value in some
signals but the Linux program always read FF from the data bus.

I want to know why? and Where I can find more information?