Disabling MCLR on Pic 16f628a

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Newz2000
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Disabling MCLR on Pic 16f628a

Post by Newz2000 » Thu Jun 16, 2005 9:43 am

I've noticed the 16f628a allows you to use MCLR as an i/o. Can anyone point out the pros and cons of doing so?<p>I like the fact that 16f628a is *cheap* and can have up to 16 i/o pins using the internal clock. If I disable MCLR and use the two USART pins for serial communications it will give me just enough to do what I want w/out using shift registers.<p>Has anyone disabled MCLR and regretted it later?

hp
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Re: Disabling MCLR on Pic 16f628a

Post by hp » Thu Jun 16, 2005 10:15 am

The MCLR pin will only function as an input in I/O mode.<p>I don't know what your project is, but the input mode has worked for me before.<p>I don't see any problems with using the MCLR pin as an input. The only major problem I see is if you are using ICSP. This would probably cause conflicts if you don't disconnect the pin.<p>(Take a look at the 16F628 datasheet at http://ww1.microchip.com/downloads/en/D ... 40044D.pdf - page 10 - 11 gives the pin info)<p>Harrison

Gorgon
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Re: Disabling MCLR on Pic 16f628a

Post by Gorgon » Thu Jun 16, 2005 12:56 pm

Hi Matt,
Since MCLR- is the Vpp input you need to protect the output of your circuit with a resistor and maybe a 5v1 zener diode behind this.<p>You also need some resistors on the b6 & 7 lines as well. All these pins are used by the ICSP.<p>TOK ;)
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

Newz2000
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Re: Disabling MCLR on Pic 16f628a

Post by Newz2000 » Thu Jun 16, 2005 1:38 pm

Thanks, I will be using ICSP. At this point it won't be until next week before I get back to this circuit so I'll probably have some more specific questions then.<p>I'm really pleased with the features and price of this 16f628. I realize the 16f88 has even more, but I really don't need that stuff and this is only $2.24. What a bargain.

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philba
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Re: Disabling MCLR on Pic 16f628a

Post by philba » Thu Jun 16, 2005 3:40 pm

I've run into problems on other PICs when using ICSP with mclr as an i/o pin and the internal oscillator. iirc, I made an icsp adaptor that used a 10K pu for mclr to get it to work. I don't know if the 628A has problems here.<p>Then you'll really like Mouser - 628A I/P (industrial dip) for $1.73, 16F88s for $2.60<p>I switched all my 18 pin designs over to the 16F88 because you can bootload it. ICSP is great but when the device is mounted in an inconvienent location, its a lot easier to sneak in serial than ICSP.<p>[ June 16, 2005: Message edited by: philba ]</p>

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