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gjs_rsdi
Joined: 06 Feb 2006
Posts: 468
Location: Bali
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| PIC16F1847 MCLR pin |
 Posted: Sat Jun 10, 2017 8:53 pm |
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Hi
I have a problem to understand what is correct regarding pin A5, MCLR pin.
In the data sheet page 13 is written regarding RA5 "General purpose I/O."
In the data sheet page 122 is written "...RA5 is an input only"
Can someone tell me what is correct?
Best wishes
Joe |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jun 10, 2017 11:02 pm |
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On page 46 in the MCLRE section, it says:
| Quote: | | MCLR/VPP pin function is digital input. |
On page 77, it says:
| Quote: | 7.4.2 MCLR DISABLED
When MCLR is disabled, the pin functions as a general purpose input and the internal weak pull-up is under software control. |
On page 119, it says:
| Quote: | 12.3.1 DATA REGISTER
The exception is RA5, which is input only and its TRIS bit will always read as ‘1’. |
On page 120 it says:
| Quote: | | TRISA5: RA5 Port Tri-State Control bit. This bit is always ‘1’ as RA5 is an input only. |
In other words, they made a mistake when they said it's an i/o pin.
But everywhere else they say it's input only. You could tell them
about the documentation error if you want to. This page has a link
to email their technical document team:
http://www.microchip.com/about-us/contact-us |
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gjs_rsdi
Joined: 06 Feb 2006
Posts: 468
Location: Bali
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| Posted: Sat Jun 10, 2017 11:13 pm |
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Thank you for the answer PCM programmer 
Best wishes
Joe |
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temtronic
Joined: 01 Jul 2010
Posts: 9100
Location: Greensville,Ontario
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| Posted: Sun Jun 11, 2017 5:00 am |
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Maybe it's because I've been in this since PICs had quartz windows and Assembler was THE programming language but 'i/o' means a pin that is used for input or output or both, unlike say a POWER pin that well, is only used to supply power to the PIC.
These days PICs have more FUSES than instructions ! Some even have more peripherals available than anyone could ever use, all in a package smaller than your fingernail !!.
That's why it is very,very important to read every one of the 500+ pages in the 'datasheet'.
Jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19217
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| Posted: Sun Jun 11, 2017 12:00 pm |
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Absolutely.
In the general pin description, you have the power pins, any special control /voltage pins, and then the I/O pins. You have to look at the data sheet to know what the individual I/O capabilities of each pin are.
However the line in the data sheet listing this as a 'general purpose I/O', is undoubtedly wrong...  |
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gjs_rsdi
Joined: 06 Feb 2006
Posts: 468
Location: Bali
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| Posted: Sun Jun 11, 2017 2:34 pm |
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I agree that:
| Quote: | | ...very important to read every one of the 500+ pages in the 'datasheet' |
and I always read carefully the data sheet. It is not difficult as I am working just with 18F26K22, 18F46K22 and 16F1847.
I just wanted to be sure as the line stating I/O contradicts all the other statements about the pin.
Better to ask a question from people that have better knowledge than me than making a stupid design
Best wishes
Joe |
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