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Strange problem with String length in 8051


Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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say2paul

Sat Aug 02 2008, 04:32AM

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I am facing a very strange problem with string length in my program.

I am getting following compiler error with Keil compiler:
*** ERROR L107: ADDRESS SPACE OVERFLOW
SPACE: DATA
SEGMENT: _DATA_GROUP_
LENGTH: 002EH
Program Size: data=111.2 xdata=0 code=2709

The problem occurs if I take the size of string more than 40 i.e. char str[50]

But if I reduce the size of string to 40 or less than 40 then code compile without any error.

Please help me I need a string of around 160 length so that I can send an SMS using that string.

pdi33

Sat Aug 02 2008, 09:12AM

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hi say2paul,
maybe the problem is because the string is occupying the valuable RAM space( which is only 128 bytes in case of 8051). If the string is a fixed value ( u r not modifying the content in the program), try changing it to the following:
constant char str[50]
this will ensure that the string is stored in the program memory space instead of occupying the data RAM.

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say2paul

say2paul

Sat Aug 02 2008, 10:26AM

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pdi33 wrote ...

I cannot take it as constant as I need to append data to same string..

I think idata can work in this case as I am using AT89C55WD with 256 bytes of RAM.

sashijoseph

Sat Aug 02 2008, 11:22AM

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Yup...an idata variable should work.It allows you to use all of the 256 bytes.

Let there be music........

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say2paul

say2paul

Mon Aug 04 2008, 04:27AM

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Can I use AT24C08 (external memory) instead??

[ Edited Mon Aug 04 2008, 04:28AM ]

say2paul

Tue Aug 05 2008, 12:31AM

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Anybody . . !

Ajay

Tue Aug 05 2008, 09:13AM

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128 bytes of memory of 8052 architecture is accessible directly using variables stored in ram, rest of 128 can only be accessed using indirect addressing.

as sashi said try using idata (use the indirect part of your controller ram)

e.g.

CODE:

unsigned char idata abc[50];

 

also if you want to use the external memory, its good but i would say a hectic process as reading and writing from eeprom is slow.

try giving idata a chance

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say2paul

pdi33

Tue Aug 05 2008, 11:30AM

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hi say to paul,
As so truely said by ajay, EEPROM programming is slow but if u are planning to use 160 bytes for ur application ,then the uC will have only 96 bytes for all the other processing including the stack.
So i feel u should keep the other global variables and static variables to a minimum. Try using local variables (variables inside functions) wherever possible so that the same RAM can be reused by the uC for multiple functions making the code more efficient.
good luck.

* inspired to develop,developing to inspire *