Hi there,
I have just read the theory about internal architecture of 8051 I/O ports.
According to theory P1 to P3 should be HIGH if they are to be used as input ports.Because if PORTS are LOW then the internal mosfet will always hold pin status as low (Refer the attached diagram )and cant be changed ...making it useless as an input port.
so I tried to test this condition, I made Port1 LOW... connected an active HIGH switch to P1.0 pin and read the pin status after pressing switch and...
AT89c51 GPIO interfacing
I have just read the theory about internal architecture of 8051 I/O ports.
According to theory P1 to P3 should be HIGH if they are to be used as input ports.Because if PORTS are LOW then the internal mosfet will always hold pin status as low (Refer the attached diagram )and cant be changed ...making it useless as an input port.
so I tried to test this condition, I made Port1 LOW... connected an active HIGH switch to P1.0 pin and read the pin status after pressing switch and...
AT89c51 GPIO interfacing