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I am using an 8051 (C51/BL51) with no off-chip memory. I have two functions with parameters:
void Detect( U8 iLed )
and
static U8 INHSampleHandler( U16 u16Sample )
Now I understand that Keil will allocate a variable (in DATA) for these. The problem seems to be that the locator is using the same memory location for both. I cannot understand why.
Below are excerpts from the scratchpad showing 2 "D:0026H". These are the only places these symbols are declared. Any ideas what I'm doing wrong?
Thanks, Jeff
BL51 BANKED LINKER/LOCATER V5.12 07/14/2011 09:36:23 PAGE 1 BL51 BANKED LINKER/LOCATER V5.12, INVOKED BY: Z:\TOOLS\SOFTWARE\KEIL\BL51.EXE Z:\Software\FB_CPU_Init.obj, >> Z:\Software\Settings.obj, Z:\Software\Glo >> bals.obj, Z:\Software\Devices\Clock.obj, Z:\ >> Software\Devices\Flash.obj, Z:\Software\Devices\HMI.obj >> , Z:\Software\Devices\INH.obj, Z:\ >> Software\Devices\ADC.obj, Z:\Software\Devices\Timer.obj, Z >> :\Software\Builds\TestINH - 06-00039-21-09\Main.obj >> , Z:\Software\Test\Test_Button.obj, Z:\So >> ftware\Builds\TestINH - 06-00039-21-09\Version.obj TO Z:\ >> Software\Builds\TestINH - 06-00039-21-09\06-00039-21-09-xx.wsp >> RS (256) PL (68) PW (78) XDATA (?XD?SETTINGS (0X0)) CODE (?CO?VERSION (0X7 >> FC0)) MEMORY MODEL: SMALL Deleted for brevity ------- PROC _INHSAMPLEHANDLER D:0026H SYMBOL u16Sample C:0BF1H LINE# 150 C:0BF5H LINE# 151 C:0BF5H LINE# 207 C:0BF7H LINE# 208 ------- ENDPROC _INHSAMPLEHANDLER ------- ENDMOD INH Deleted for brevity C:09FEH PUBLIC _Detect C:074EH PUBLIC main ------- PROC _DETECT D:0026H SYMBOL iLed
"One moment, you're criticising fine detail and ignoring the context; then, just to be contrary, you decide to do the opposite!"
I thought I had answered that, in the post that yours above responded to.
but in case you missed it, sometimes fine details matter, and in other cases, they don't.
so it is hard and wrong to insist that one always pays attention to fine details - they are called "fine details" for a reason.
hope it helps.
Making a bold statement like "There are NO problems" - with the big emphasis on the NO - is not a fine detail. It is plain wrong.
this is exactly what IB wrote:
'There's NO problem with calling a function from an '51 ISR.
However, like most tasks, the programmer needs to understand the mechanism(s) involved and take appropriate steps to ensure the cogs fit correctly.
FWIW, we have plenty of code that calls functions from ISRs. It's all written in assembler and there have been no reported problems. Quite a few of those functions are inherently re-entrant. They are called from both ISR and mainline code. Most importantly, parameters and local variables are passed in registers.
No problem, so long as you know what you're doing, period.'
vs. what you characterized what he wrote:
"There are NO problems"
come on. would any reasonably intelligent people equate the two?
as I stated before, the two of you said the same thing, with different emphasis. and there is no point in pushing any of your statements to the extreme to justify the other.
"Erik (who is not afraid of putting his name to his statements)"
how heroic you are!
on that basis along, they should award you the Nobel prize for Bravery and two Metals of Honor (not just one!)
You want to hide your spewing bile behind anonymity, I am, at least, willing to stand behind what I post.
Erik
"I am, at least, willing to stand behind what I post."
far more importantly, you have the bravery to put your name to your statement, as you proudly and publicly stated.
and that's just extremely heroic, and because of that and that alone, you should be the target of national admiration.
thus I think you deserve not just the nobel prize for bravery but also two (not just one) Metals of Honor!
"True, the problems will not be significant in some designs..."
So how low down the significance scale exactly is no problem? I described how I have written plenty of assembler functions that were inherently re-entrant.
"...but, again, just saying there are "NO" problems is unhelpful."
But when does a professional/experienced programmer learn that what they've always been told they cannot do can in fact be done?
Saying it is unhelpful, I think, in itself is unhelpful - And doing a disjustice to budding competent future professional programmers.
There are quite a few professional programmers here. Do they think that what I suggested cannot work? If they do, then I'd (unfortunately) have to say that maybe they're not quite as professional as they think.
"Because Keil C51 functions are inherently not reentrant (due to the Overlaying) ..."
Actually, that is not totally true. If one were to take the time to read the Keil documentation, they'd learn that it is in fact possible to write inherently re-entrant functions in Keil C51 (and I don't mean by using the reentrant keyword). Of course there are limitations. The functions would generally be small, take few parameters and use few local variables - Just the sort of sensible function that could be included into an ISR.
So how low down the significance scale exactly is no problem? I described how I have written plenty of assembler functions that were inherently re-entrant. the thread is about C
"...but, again, just saying there are "NO" problems is unhelpful." there are, indeed, - you say so yourself - some problems
pray show a function that "don't use the reentrant keyword" and "use few local variables" and is "inherently re-entrant".
"pray show a function that "don't use the reentrant keyword" and "use few local variables" and is "inherently re-entrant"."
Erik, I really expected better of you.
Anyway - As a starting point, take the simple/obvious example:
void foo(void) { ; }
You'd find it difficult to get fewer local variables. It doesn't need reentrant. It doesn't require any overlaying of data (simply because there isn't any).
In the past I have said to our junior trainees: "Here is the start. You have the manuals. Expand a step at a time and see how far you get".
If you have a few spare minutes, you could give it a go. The manuals really do have all the necessary information.
"the thread is about C"
Yes, it is.
And that is precisely the reason why I dislike reading the statement:
"If at all possible, avoid calling any functios from a '51 ISR, period."
The budding professional might well read that and quite literally take it to assume it includes any scenario.
"Making a bold statement like "There are NO problems" - with the big emphasis on the NO - is not a fine detail. It is plain wrong."
Well, thanks for that vote of confidence ;)
However - I do not believe it is wrong at all. There aren't any problems - So long as everything about the situation is understood. Nothing specific about '51 architecture there.
If I were to say that there were no problems with boiling an egg I guess I'd get a complaint from someone pointing out that it shouldn't be done because someone might leave the gas on and the house might burn down.
Just because you've managed to avoid the problems does not mean that there are no problems.
Just like crossing the road has many dangers - but most of us manage to do it every day by being aware of the dangers, and acting accordingly.
But saying there are NO dangers is untrue and unhelpful.
"Just because you've managed to avoid the problems does not mean that there are no problems."
Andy, what problems are you talking about? I certainly didn't have to avoid any problems. There weren't any problems in what I did. Why? because I understood how the 51 works, how the assembler works, what the compiler produced, how the linker works, and what I wanted to achieve. There were no problems and no gotchas.
"Just like crossing the road has many dangers ..."
That's an extremely poor example. Processors are (in general) highly predictable. Crossing the road is totally different. You are not in control of all the variables - Most importantly there is that unknown variable sitting behind the wheel of a large mass.
"But saying there are NO dangers is untrue and unhelpful."
That seems to lack a certain amount of context. Go back and you'll see my post ended with:
No problem, so long as you know what you're doing, period.
So ... going back to the full post and full context, what I was saying is that there is no danger in doing it per se. You (and others) might consider it a danger in the context of Keil's implementation of C - But in itself I stand by what I said.
"Just like crossing the road has many dangers - but most of us manage to do it every day by being aware of the dangers, and acting accordingly."
which of the following statement would you agree more?
1) don't cross the road (because there is danger); 2) it is OK to cross the road, as long as you understand the danger.
I would rephrase it like this:
"Would you like to establish a _habit_ of crossing the road at a dangerous spot for 10 other people, when you know that the risk involved is significant"?
To me, the question is not if it is dangerous or not. Risk can be managed, at least on the short term. The question is whether this is sustainable on the long term.
my post was triggered by it is in fact possible to write inherently re-entrant functions in Keil C51 (and I don't mean by using the reentrant keyword). Of course there are limitations. The functions would generally be small, take few parameters and use few few is not none local variables
thus
void foo(void) { ; } You'd find it difficult to get fewer local variables. It doesn't need reentrant. It doesn't require any overlaying of data (simply because there isn't any).
of course not, with no local variables what I asked you to do was to show it "with a few local variables" as you stated would be no problem