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
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