PIC and 74ls47

[casebsantos]

Hi All ,

i have built a circuit that connect pic16f84a 74ls47 and a coomn anode seven segmant.

i have a aproblem now that all the inputs of the 74ls47 gives 1.3 volts , i don't why.

for that reason my pic ports that connected to the 74ls47 is also 1.3 volts , even if i removed the pic IC .

[mississippi1]

An open input of a TTL Ic ia always floating at 1,3 volt. A not programmed pin of a 16F84a is also an input. If you program (tris register) a pin for an output, and the output is an open drain one, than you will need a pullup resistor (4K7) for to drive a TTL ic.
Maybe the answer of your problem is written now here.

[casebsantos]

Very good mississippi1 .

It is this same. It was valid for the tip!

Thaks a lot.

[yobalzal]

A suggestion, if you are running your project ob batteries, you can use 10K instead pf 4K7, you'll save some current by reducing loading.

Cheers...

[casebsantos]

A suggestion, if you are running your project ob batteries, you can use 10K instead pf 4K7, you'll save some current by reducing loading.

Cheers...

I am using an resistance of 10k.