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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| the history of pin RA_4 PIN_A4 [ solved!! ] |
 Posted: Tue Mar 19, 2013 10:27 am |
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i am used to the fact that pin_a4
is open collector on 16C/F and 18F parts
1- are there any parts where A4 is NOT OC?
2- does anyone know the history of this.
Last edited by asmboy on Tue Mar 19, 2013 4:30 pm; edited 1 time in total |
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bkamen
Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA
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| Re: the history of pin RA_4 PIN_A4 |
| Posted: Tue Mar 19, 2013 10:38 am |
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| asmboy wrote: | i am used to the fact that pin_a4
is open collector on 16C/F and 18F parts
1- are there any parts where A4 is NOT OC?
2- does anyone know the history of this. |
I do not know the history of this.
It is an interesting question though....
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19515
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| Posted: Tue Mar 19, 2013 12:51 pm |
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It was the pin used for Vpp on many of the earlier PIC's. Since it has to be taken well above Vdd, it couldn't have the upper driver transistor present, which would otherwise act as a diode.
Once chips switched to using MCLR instead, RA4 became a normal pin, except on some where this was retained for 'reverse compatibility'.
Chips like the 16F884 to 7 all have a normal A4 pin.
Most PIC18's have a normal pin here.
Best Wishes |
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Tue Mar 19, 2013 3:35 pm |
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awesome thread.
often wondered this my self.
G.
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CCS PCM 5.078 & CCS PCH 5.093 |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Mar 19, 2013 4:29 pm |
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| Quote: |
a normal pin here.
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God bless the normal pin 
Thank You all |
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temtronic
Joined: 01 Jul 2010
Posts: 9226
Location: Greensville,Ontario
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| Posted: Tue Mar 19, 2013 4:44 pm |
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'normal' pin ? hahaha
these days it's an input,then an output, then not there(hi-z),next it's an analog input,maybe a PWM output,serial in, serial out,timer input,clk out,maybe a comparator input or output!!!
I think 'normal' pins left us when micrcomputers came out and replaced microprocessors.Sigh, guess I'm showing my age again !
i just wished these new PIC would default to basic Digtal I/O and not the 'extra fun stuff'.
cheers
Jay |
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