SFR's as RAM ?
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SFR's as RAM ?
by PICdude-3
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Other than being bad form, are there any problems with using SFR's
such as ADRESH and ADRESL for some temporary RAM space (assuming the ADC is off)? Cheers, -Neil. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Jinx-4
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Hey Neil
> Other than being bad form, are there any problems with using SFR's > such as ADRESH and ADRESL for some temporary RAM space > (assuming the ADC is off)? ISTR Microchip suggest using unaccessed SFRs as general purpose RAM in the datasheet. 'bad form' can manifest itself in many ways if you don't know what you're doing or don't pay attention ;-) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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RE: SFR's as RAM ?
by Michael Rigby-Jones-2
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> -----Original Message----- > From: piclist-bounces@... [mailto:piclist-bounces@...] On Behalf > Of Jinx > Sent: 29 October 2009 08:54 > To: Microcontroller discussion list - Public. > Subject: Re: [PIC] SFR's as RAM ? > > Hey Neil > > > Other than being bad form, are there any problems with using SFR's > > such as ADRESH and ADRESL for some temporary RAM space > > (assuming the ADC is off)? > > ISTR Microchip suggest using unaccessed SFRs as general purpose > RAM in the datasheet. 'bad form' can manifest itself in many ways if > you don't know what you're doing or don't pay attention ;-) The HiTech compiler uses some SFRs for temporary storage if they aren't being used. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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RE: SFR's as RAM ?
by PICdude-3
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Well this is good to know.
Jinx: of course I always know what I'm doing ... at least until something smokes. Cheers, -Neil. Quoting Michael Rigby-Jones <Michael.Rigby-Jones@...>: > > >> -----Original Message----- >> From: piclist-bounces@... [mailto:piclist-bounces@...] On > Behalf >> Of Jinx >> Sent: 29 October 2009 08:54 >> To: Microcontroller discussion list - Public. >> Subject: Re: [PIC] SFR's as RAM ? >> >> Hey Neil >> >> > Other than being bad form, are there any problems with using SFR's >> > such as ADRESH and ADRESL for some temporary RAM space >> > (assuming the ADC is off)? >> >> ISTR Microchip suggest using unaccessed SFRs as general purpose >> RAM in the datasheet. 'bad form' can manifest itself in many ways if >> you don't know what you're doing or don't pay attention ;-) > > The HiTech compiler uses some SFRs for temporary storage if they aren't > being used. > > Regards > > Mike > > ======================================================================= > This e-mail is intended for the person it is addressed to only. The > information contained in it may be confidential and/or protected by > law. If you are not the intended recipient of this message, you must > not make any use of this information, or copy or show it to any > person. Please contact us immediately to tell us that you have > received this e-mail, and return the original to us. Any use, > forwarding, printing or copying of this message is strictly prohibited. > No part of this message can be considered a request for goods or > services. > ======================================================================= > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Bob Axtell
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> Other than being bad form, are there any problems with using SFR's
> such as ADRESH and ADRESL for some temporary RAM space (assuming the > ADC is off)? > > Cheers, > -Neil. > Nope. I almost always use up TMR2, TIMER1, PR2, ADRESL. I think ADRESH is less than 8 bits. I've even used SBRGH (sp?) sometimes when I don't need a serial port. Another uncommon use for SFR's is that when you are writing code for slight variants (PIC16F876A vs PIC16F877A) I test different SFRs to determine what processor is running, so I can know about analog, port availability, etc. That way, the code can be universal with slight different branches in the code. --Bob -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Dario Greggio (in giro)
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Charles Craft ha scritto:
> When/how do you test a SFR? > Pre-processor, compiler, linker, runtime? > > I suppose runtime, in this case... -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Tamas Rudnai
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On Fri, Oct 30, 2009 at 1:00 AM, Dario Greggio <adpm.to@...> wrote:
>> When/how do you test a SFR? >> Pre-processor, compiler, linker, runtime? >> > > I suppose runtime, in this case... Does it mean that the binary (compiled code) can run on many different PIC? I suppose the variation of the target would be quite limited anyway? Tamas -- /* www.mcuhobby.com */ int main() { char *a,*s,*q; printf(s="/* www.mcuhobby.com */ int main() { char *a,*s,*q; printf(s=%s%s%s, q=%s%s%s%s,s,q,q,a=%s%s%s%s,q,q,q,a,a,q); }", q="\"",s,q,q,a="\\",q,q,q,a,a,q); } -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Dario Greggio (in giro)
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Tamas Rudnai ha scritto:
> On Fri, Oct 30, 2009 at 1:00 AM, Dario Greggio <adpm.to@...> wrote: >>> When/how do you test a SFR? >>> Pre-processor, compiler, linker, runtime? >>> >> I suppose runtime, in this case... > > Does it mean that the binary (compiled code) can run on many different > PIC? I suppose the variation of the target would be quite limited > anyway? yes, indeed I agree... -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Barry Gershenfeld-2
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> > Does it mean that the binary (compiled code) can run on many different
> > PIC? I suppose the variation of the target would be quite limited > > anyway? > Remember that the instruction sets across a PIC family (PIC16F, for example) are identical. That means that from chip to chip, it's the peripherals that may or may not be there. Probably the most extreme example of this reuse thing is in the 18F chips, where unused USB buffers can be used as RAM, and there are several K bytes of space there. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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Re: SFR's as RAM ?
by Ruben Jönsson
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>
> Probably the most extreme example of this reuse thing is in the 18F chips, > where unused USB buffers can be used as RAM, and there are several K bytes > of space there. > -- Anoter way to get "free ram" is if you use a character LCD. The controller always has DDRAM for 4*20 characters even if the display has less. Unused (not visible) character positions can be used as RAM. Only remember to not use instructions that affects all DDRAM, like Clear Display. /Ruben ============================== Ruben Jönsson AB Liros Electronic Box 9124, 200 39 Malmö, Sweden TEL INT +46 40142078 FAX INT +46 40947388 ruben@... ============================== -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist |
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