PIC problems

[flawed]

hi, i was wondering if i could get abit of advice.

Using an example from a book i've been working through, i have built a breadbord for using a pic 16f84a to control the old hitachi lcd controller (in 8 bit mode) , but the project i have in mind requires more i/o so i'm basically just trying to adapt the same code and circuit for the 28 pin 16f876a.
So far i have simply replaced the pic, pulled all the unused pins to +5 through 10k resistors and set them as outputs in picBasic, and just changed the complie options, but it isn't working with the 28 pin.

I've just read on the data sheet that the 16f876a runs from a 20MHz oscillator, where the example project on the uses a 4/mhz rytal, can the 28 pin device also run on 4/mHz? or will i have to change the clock and adjust the delay signals etc for it to communicate with the lcd?

any advice or where to get the answers would be greatly appreciated.
thanks for looking

 

[eng1]

I've just read on the data sheet that the 16f876a runs from a 20MHz oscillator, where the example project on the uses a 4/mhz rytal, can the 28 pin device also run on 4/mHz? or will i have to change the clock and adjust the delay signals etc for it to communicate with the lcd?

It can run at 4 MHz. 20 MHz is the max oscillator frequency.

Using an example from a book i've been working through, i have built a breadbord for using a pic 16f84a to control the old hitachi lcd controller (in 8 bit mode) , but the project i have in mind requires more i/o so i'm basically just trying to adapt the same code and circuit for the 28 pin 16f876a.

Have you considered using the 4-bit interface? Or do you need more than 4 additional I/O pins?

 

[vili.chaudhary]

Hi,
I am not quite sure if I got your question right.

I've just read on the data sheet that the 16f876a runs from a 20MHz oscillator, where the example project on the uses a 4/mhz rytal, can the 28 pin device also run on 4/mHz? or will i have to change the clock and adjust the delay signals etc for it to communicate with the lcd?

20MHz is the max you can use for the 16F87XA PICs. So the answer to your question is YES. It will definitely work on a 4MHz crystal.

Regards,
Vili

 

[Nigel Goodwin]

Hi,
I am not quite sure if I got your question right.



20MHz is the max you can use for the 16F87XA PICs. So the answer to your question is YES. It will definitely work on a 4MHz crystal.

PIC's will run from DC to above their maximum specified frequency, they are extremely versatile.

 

[flawed]

cheers. So there isn't any fundamental differences between the two which will prevent me from using the same code and circuit (except coding for port c an some reg. address changes)

 

[Nigel Goodwin]

cheers. So there isn't any fundamental differences between the two which will prevent me from using the same code and circuit (except coding for port c an some reg. address changes)

No, they use the same 14 bit core - you might check my tutorials for the changes required when going from 16F628 to 16F876/7.

 

[flawed]

fantastic. thanks for helping