in the attched CKT i am giving vcc as 3.3V driving the latched Input/Output pin and form latched pin i am connected as shown in the figure attached. but does this LED glow?
Since at the Anode side is connected to 3.3V and the Cathode side is also connectd to 3.3v thorugh 510ohms.
hi
i think the above shown circuit do not work as u say that both the terminals are at same potential , and there is no Flow of current through LED , and thus the LED will not GLOW..
Yes, You are right. The R27 resistor is an external pullup which will be useful if you are sourcing an external current when the port pin is high. In your application, the port bit need to sink the LED current and in this case, R27 is not required, it only adds to the current to be sunk by the port pin when low.