You have to Disable the parallel port first before you can read the 8 data input bits. . The below code will do that.
Regards,
Charles Bannister

outp( pdata, 0xff );
// set LPTx port data high
outp( pctrl, 0x24 );
// disable LPTx port data driver
outp( pctrl, 0x26 );
// enable read data buffer
delay(10) );
// delay 10 mS
tmp = inp( pdata );
// get data
outp( pctrl, 0x04 );
// control signals inactive
outp( pdata, 0 );