Hi,
I'm wondering if I am doing something wrong here. I am trying to store an array for a large 256 byte look-up table.
I have a pretty small 8051 MCU of 8 KB flash memory (IROM), 256 bytes internal RAM (IRAM) and 256 bytes on-chip external RAM (XRAM).
Prior to adding this look-up table, my current build from Keil reports:
"Program Size: data=54.1 xdata=0 code=1984"
I take that to mean I am using 54 bytes of IRAM, 0 bytes of XRAM, and 1984 bytes of IROM?
Here is the variable declaration I am using:
code unsigned char CRC8LookupTable[256];
When I define the CRC8LookupTable and populate values, I get the Segment Too Large error.
If you use "code" doesn't that store the values in ROM, which I should have plenty of space for?
Is there something else I need to add to that variable declaration?
Thanks -Tim
unsigned char code CRC8LookupTable[] =
will do it
I CONCUR WITH MR ERIK
Hi guys,
(Sorry I dumped a junk thread.. and didn't reply to this... just want to leave this here for the next guy)
Thanks for the help! Last night, I was lying in bed and came across the manual section it stated that you need to declare & define the code variable in one statement.
I had read it earlier, and had tried to declare & define my array in my header, but had not tried to declare & define in the source.
So just for posterity, here is what I had that was not working:
crc.h
unsigned char code CRC8LookupTable[256];
crc.c
CRC8LookupTable[256] = { 0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD, 0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A, 0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42, 0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4, 0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34, 0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83, 0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 };
Here is what WORKS for the syntax and compiler:
<INTENTIONALLY BLANK>
unsigned char code CRC8LookupTable[] = { 0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD, 0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A, 0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42, 0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4, 0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34, 0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83, 0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 };
This also works:
unsigned char code CRC8LookupTable[256] = { 0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD, 0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A, 0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42, 0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4, 0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34, 0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83, 0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 };
----
I had tried declare & define the code array in the header, which did not work and did not try to declare & define in the c source. So there you have it, DON'T declare a code variable in the header and define it in the source. DO declare & define a code variable in the source.
This software is being run on kind of a 3rd tier 8051 manufacturers MCU (I don't want to name names as their engineers are working with me to try fix the problems). Their current 8051 MCU doesn't fully support the debugger in Keil [doesn't support breakpoints when an ISR is defined AND doesn't debug within an ISR at all), so I was getting worried maybe something else was broken....
CRC messaging routine to be coded today it looks like... fun.
Thanks to all to clear this up. I came in to work at 8:30AM on a Saturday to try this!
here is what I had that was not working:
CRC8LookupTable[256] = ...
But your definition there does not match the declaration - the type & 'code' qualifier are missing!
Surely, it should have been:
extern unsigned char code CRC8LookupTable[256];
unsigned char code CRC8LookupTable[256] = ...
@Andrew
The behavior is really weird. I'm not a wizard at C or compiler mechanics.
If you do not declare and define the array like this.
You can declare like this in the header:
But unless you define & declare the array in the source, it doesn't place the array in the flash memory... It is almost like the header declaration has no bearing on getting the array into the flash.
To me, I kind of expect that you would declare the array with the code statement, and then define it in the source code like any other variable. But, definitely not. I'm sure there is a compiler reason for this.
It seems like the compiler ignores the declaration in the header if it has code in the declaration.
Adding the declaration to the header, maybe it helps the compiler? But seems like the compiler expects the declaration and definition in the source.
Just for sake of completeness, Andrew is right about the header, it is not ignored. I know because I just spent 15 minutes trying to massage the declaration and definition correctly.
To call the table from other files here is the final declaration and definitions I needed to use.
//This holds the 256 possible byte combinations for the CRC8 polynomial. extern unsigned char code CRC8LookupTable[256];
//This stores the lookup table in the program flash memory through the "code" unsigned char code CRC8LookupTable[256] = { 0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD, 0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A, 0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42, 0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4, 0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34, 0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83, 0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3 };
Bizarre, but it works and I can call it from other source files.
Bizarre, but it works and I can call it from other source files. what is bizarre about things working when they are done right?
I do not know if, for some reason, your original mess would be supposed to work, but a compiler that fails because of code in a header file is, in my opinion, bug free
@Erik -- If you were building a compiler, why would you treat the case where you put code and require that to be declared and defined in two places?
When are other variables used like that? I'm sure there is a reason from a compiler perspective, but from an end user perspective when you shift around fundamental behaviors like that, it seems a bizarre.
Have you ever read the definition of bizarre? It doesn't imply standard of "rightness" or "wrongness" -- it is just unusual, as in atypical usage of a variable in C...
When you say things are "right" with Keil's compiler -- it's pretty relative. I'm not getting metaphysical on a compiler. We aren't just a Keil C51 shop in my business.
PIC's compiler at least provides an error that you need to declare and initialize at the same time if you use const. In that sense, as being more clear does make it their compiler "better"? Maybe Keil could add a similar warning to their compiler, and make it easier to use. Doesn't seem like a crack-pot idea. Easier products for end-users, more end users who make more money using the tool... seems pretty straightforward.
Geez man - I don't get your snark. Do you work for Keil?
A compiler is a relative construct -- likewise conforming C standards. Whatever -- just a tool for a job. I don't have any religious zeal to software languages and standards. I try to write good code that is portable and re-usable. But I am all moving bits around for money. I'm surely not putting in a CRC routine, on a beautiful spring, just because.
I literally don't care how Keil wants to implement things. Seriously. Their product, their compiler -- whatever. They can do it anyway they want. I would wish maybe they illustrated this point a bit better in their documentation, and maybe called it out with a more direct warning in their compiler.
End of the day -- we are building a cheap device using an 8051 and we plan to move thousand of units a month using these 8051s and save a bundle of money versus a PIC based implementation on each unit. If I have to fiddle with some Keil C51 semantics, no biggie.
Forum post is here for the next user, to save them some time. Mission accomplished. I'm out. I won't respond to anymore.
Way to be a nice neighbor, man. Remind me NOT TO EVER ASK YOU FOR PAID CONSULTING. You never know who is on the other end of the forum. Maybe we need some really tight assembly for one of these low-end MCUs, we pay $130/hr for good assembly all day long...
I don't see how that is in any way bizarre?
That is the standard way that you would declare & define a variable in 'C'.
The Keil-specific 'code' qualifier is applied in exactly the same way as the standard 'volatile' and 'const' qualifiers.
c-faq.com/.../decldef.html
Qualifiers. Good word to learn, didn't know that. I told you I am not a C wizard.
Okay -- so, for volatile & extern and other qualifiers. You don't re-use them when you define the variables in the source, right?
I only use the qualifier for volatile in the declaration, right? (add in an extern if you want too!)
volatile unsigned char SomeData;
Now we go to the source, no more qualifier required since it is in the declaration in the header.
unsigned char SomeData = 1;
Great we got variable we can use safely with interrupts. But volatile qualifier required in the definition? How is that not bizarre, how qualifiers are used differently between these cases?
I'm sure their is a reason for the compilation process, but I'm talking about end user experience here of someone typing in text.
Then you have the example of CODE as a qualifier. It has to be used as a qualifier in both the declaration and definition unlike volatile?
For my knowledge, does Keil C51 treat the XDATA qualifier the same way?
I'm sure one day I'll need to tap into XDATA. I was looking at the memory model stuff and everything else while diving into this yesterday.
CONCUR WITH MR ERIK
No. Quite the opposite: you do "re-use" them!
The declaration must match the definition in both type and qualifiers
If you're sharing the declaration with other modules (and why else would you put it in a header file?) you add 'extern'
some.h
extern volatile unsigned char SomeData ;
some.c
volatile unsigned char SomeData = 1;
Only a definition can contain an initialisation.
Are you sure on volatile? I'm looking at some code from another programmer who built some PIC routines, and I see they use volatile on both the definition and declaration.
Are you sure that the compiler cares? If you add volatile to the definition or not when you initialize the variable, the compiler doesn't utter a warning / error either way. I'm sure there is some way (memory map or something) to see if the variable is being optimized or not.
But for extern, you clearly need it in the declaration....
I actually appreciate the help Andrew! This like a master class in qualifiers...!
I have no skin in the game -- if the compiler wants volatile in both declaration and definition. It can have them!
TECHNICALLY YOU DONT NEED THE EXTERN IN THE DECLARATION IN A HEADER (IN C) BUT IT IS COMMON TO SEE IT THERE.
STOP SHOUTING!
The 'extern' is only optional for function declarations (ie, prototypes):
www.youtube.com/watch
HA? You guys know this one?
Good stuff here today.