creating new port

[ssaakmnt]

I am trying to run 4 7segment displays directly from pic16f877 , 3 displays for port b,c and d , port a has not enough pins to drive the 4th display so the idea is to build new port consist of port a pins and port e pins can we do that ? , I tried this code but didn't work:

[Mike Walne]

Yes you can.

But I feel it's simpler to multiplex.
Frees up loads of pins.
I'm assuming you're using LED displays.
And you've included current limit resistors in each segment lead.

So:-

1) Connect all 4 segments a together to say C0
2) Same for b,c,d,e,f,g,dp to C1,,,,,,C7.
3) Common of display 0 to D0
4) Same for commons 1,2,3 to D1,D2,D3.

Then:-

Turn each display on in turn for say 1ms each.

Can't help further until we know if you're using CA or CK displays.

Mike

[temtronic]

aw Mike , he's sooooo close to doing it, no need to mux !!
I did the same thing about 20 years ago when the 877 was new.

Do not use RA4 as it's 'open collector'. Instead use RE2.

Be sure to disable any analog pins though!

There is a thread or two here that explains using combining bits from different ports to become a 'byte' wide 'new' port.
As well it is covered in the CCS C manual,' somewhere'...

hth
jay

[Mike Walne]

OK. I'm not going to argue.

Though he could use A4 with CA displays.

Been caught out with that one more than once (wondering why it never goes high).

Mike

[ssaakmnt]

very good idea to operate all displays from one port each one alone for short period of time..i will try that ,
but also important to know how to combine different port bits to create new port ? I will chick the manual.

[PCM programmer]

[ssaakmnt]

Thank you.