Parallel port Control port

[elexhobby]

Hi Friends,
I read the parallel port tutorial on the site www.beyondlogic.org & experimented a bit with my computer.
In the tutorial it is written that the data port (0x378) is generally ‘Write Only’; however I found mine to be bi-directional – great!
The doubt I have is with the Control Port (0x37A). The tutorial says that the control port is Read/Write. So I sent all the control pins to high impedance state (sent F4, since some are hardware inverted). I then tried externally applying a low input (0 V) to certain pins– But it doesn’t read the external value. When I read back the control port, it simply reads the value sent earlier (F4).
Is it the case that not all control ports are bi-directional? I find mine to be ‘Write Only’.
Kindly help.

Thanks in advance.

Elexhobby

 

[sunsina]

First of All You Should Send you Program Lines

Now Check These:
1- You have Enabled EPP,ECP in you Rom Bios to Use your port as Bidrectional port
2- you Data (input or Output) is in the 1 Byte (@ Adr 0x378 ) you Must Always Read or Write Data
in that Reister
3- For Toggleing the Direction of Data you only need to change the Control Reg (0x378+2) bit #5
which is direction bit like outport(0x378+2,xxx1xxxx).
4- now you should put the Desired input on LPT Data Pins
5- Then you should Read the 0x378 Register a=inport(0x378)