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Implementing a PIC16F877A onto a circuit board

 
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Rando



Joined: 18 Nov 2006
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Implementing a PIC16F877A onto a circuit board
PostPosted: Sat Nov 18, 2006 4:57 pm     Reply with quote

Hi,
I am currently using the PIC16F877A with the CCS Software Prototyping Board in one of my classes. I would like to use the PIC without the board but I am confused to which pins have to be wired.

I am using the following pins: RA0 to read in a swtich
RA1 to read in a sensor ouput
C1 digital ouput to an h-bridge
C2 digital output to an h-bridge

I was wondering do both of the VDD and Vss pins have to be wired, and I don't plan on having a reset option....do I still need to wire the MCLR pin?

Also the datasheet lists a maximum current into the VDD pin....I was wondering what is the minimum current that can go into the VDD pin.
Thanks
Randy
Mark



Joined: 07 Sep 2003
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Location: Atlanta, GA

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PostPosted: Sat Nov 18, 2006 7:03 pm     Reply with quote

Yes and Yes. The minimum current depends on many factors, speed, driving current, preipherals, ect...
Rando



Joined: 18 Nov 2006
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PostPosted: Sat Nov 18, 2006 7:19 pm     Reply with quote

Thanks for the reply Mark... Just to get this straight I'd need the 2 VDD pins, the 2 Vss pins, the 2 input pins, the 2 output pins and the MCLR pin.
Also to wire the MCLR pin just follow the recommended MCLR circuit in the datasheet? ( p.148 figure 14-5).

This might also seem like a dumb question but as I said I've only used the chip on the protoboard........ do u need an external Socketed Oscillator?...or is that only needed if you have a timer in your program.

Thanks,
Randy
jecottrell



Joined: 16 Jan 2005
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PostPosted: Sat Nov 18, 2006 9:58 pm     Reply with quote

Quote:
Just to get this straight I'd need the 2 VDD pins, the 2 Vss pins, the 2 input pins, the 2 output pins and the MCLR pin.


That is correct. MCLR can simply be pulled up to Vdd through a 47K resistor.

Quote:
do u need an external Socketed Oscillator?...or is that only needed if you have a timer in your program.


You need some form of oscillator. Your choices are listed in 14.2. A crystal with the associated capacitors is the simplest (see table 14-2.) The resistor usually isn't necessary.

You should also have a 0.1uF cap on each of the Vdd pins as close to the pin as you can get. This will save a lot of grief later on.

John
Rando



Joined: 18 Nov 2006
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PostPosted: Sat Nov 18, 2006 10:25 pm     Reply with quote

Thank you for the quick response. I will give that a try
jma_1



Joined: 08 Feb 2005
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PostPosted: Sun Nov 19, 2006 10:32 am     Reply with quote

Greetings,

If you do not want to use an external oscillator, pick a different microprocessor. Some of the 18 series chips can run with the internal oscillator as the clock source.

Cheers,
JMA
Rando



Joined: 18 Nov 2006
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PostPosted: Sun Nov 19, 2006 10:40 am     Reply with quote

Thanks I will keep that in mind for the future. However, the school supplies the PIC16F877A and I'm just getting used to it ....so I do not think I will change the PIC.
Randy
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