hi am using 89c55 and wrote a code in c which acquires data from a serial device performs calculations and the gives an alarm when an abnormality is detected. when i compiled i got as Program Size: data=9.0 xdata=7569 code=4140. i used large memory model.it works well when i checked with keil simulator but when i burnt into my uc i don see any output. iam new to uc's should i add any eeproms before burning?? please help me out. thanks in advance.
regards, deepthi
Do you Have 8K of external RAM?
no i don have external ram but the chip has 20 K Flash Memory, 256 Bytes On-chip RAM,hex file was 14k in size which i have burnt into uc..
i need those three huge arrays all through my code so i cant avoid them, will the size gets reduced if i declare those arrays dynamically instead of static declaration and coming to this memory overlaying, thanks for giving an example.ill modify my code acc to this and will get back to u. thanks for responding all of u
Dynamic or static doesn't matter.
What matter is how much variables you need at the same time. If you need these arrays at the same time, then you need to have enough RAM for storing them.
Of an array stores constant - unchanging - data, then you can move the array into the flash, i.e. among the code. If the array contains values that are seldom changed, then you may use EEPROM or similar for storing the data. But whatever you do, you will need enough memory - of the correct type - for storing the arrays, or you will have to figure out a way to reduce the size of the arrays.
the data of these arrays is not constant but changes frequently so i think i have to go for EEPROM or external RAM.. but i don know how to interface that and use it while burning code into that..please help me out in this regard and it would be very helpful if any circuit diagram or code is given.. thanks in advance
You do _not_ burn code into the RAM. The RAM is for the variables. And as you have noted - the simulator can work with your program. So start by googling for how to connect RAM to your processor.
You do not want to use EEPROM fo frequencly changing data. If it is important that the data survives a power loss, then you should look for other alternatives, such as battery-backed RAM or ferro-electric memories. But every memory cell in EEPROM can only handle a limited number of write cycles before wearing out. This can be mitigated by having a very large EEPROM and do wear-leveling, where you use many memory cells to share the number of writes. But wear-leveling is a complex solution that should be avoided if possible.
thanks u all for responding and giving me suggetions .. ill try to solve my problem by following ur suggestion and will gat back to u if there is any problem.. thanks all of u once again..
That's not strictly true, and thinking that way can get misleading.
The 8052 processor itself knows nothing about Flash, RAM, or any other memory technology.
All the 8052 processor itself knows is that it has a CODE address space, and an XDATA address spaces - and those two address spaces are quite distinct.
The CODE address space is where instructions are fetched from for execution - but it can also be read as data. The key thing to remember is that the 8052 architecture has no way to write to CODE space - it is strictly read-only. Thus most applications will, in practice, use some kind of read-only memory technology (such as flash) in the CODE space.
The XDATA address space has both read & write data access - but instructions for execution cannot be fetched from XDATA space. Thus most applications will, in practice, use some kind of read-write memory technology (such as RAM) in the XDATA space.
Indeed!
It all rather sounds like you're trying to run before properly learning to walk!
I think you should spend some time reviewing the basics of the 8051 architecture, and then some simple, basic programming examples before continuing with this.
Standard advice:
First, you need to read the uVision Getting Started guide, and work through the example projects in it. This will give you a proper introductions to the tools, how they work, and how to use them - rather than just jumping-in blindly at the deep-end! You need to study the following documents - commonly referred to as "the bible" for the 8051:
Chapter 1 - 80C51 Family Architecture: www.nxp.com/.../80C51_FAM_ARCH_1.pdf
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: www.nxp.com/.../80C51_FAM_PROG_GUIDE_1.pdf
Chapter 3 - 80C51 Family Hardware Description: www.nxp.com/.../80C51_FAM_HARDWARE_1.pdf
Are you also a newbie to 'C' programming in general? If so, you'll also need a good 'C' textbook.
Here are some other introductory & reference materials: http://www.keil.com/books/8051books.asp www.8052.com/tutorial.phtml
You will need to read the Data Sheet for your particular processor, and the Manual(s) for any development boards, etc.
You will need to read the Manuals for the C51 Compiler, A51 Assembler, etc, etc,...
thanks alot neil for those documents and information u have given.. may be ur true that am trying to run....thanks alot once again...
can any one please explain me how to select a microcontroller based on XDATA size CODE size and HEX file size.Is it true that the particular UC should have flash memory of size >= HEX file size??
.Is it true that the particular UC should have flash memory of size >= HEX file size??
the size of the HEX file is no indication of the size of the program at hand. if you want to be sure, you must generate a .bin file using 'fromelf'. such a file such can be programmed directly onto flash, hence: if that one is smaller than the storing media, you are in business! you can also have a look at the map file, of course.
If your program requires x bytes of XDATA space and y bytes of CODE space, it should be obvious that your target system must provide at least x bytes of XDATA and at least y bytes of CODE space.
Those could be provided within the microcontroller itself, or as external memory...
So feed those criteria into this parametric search engine: http://www.keil.com/dd/search_parm.asp
That's true.
For further details, including the hex file format, see: http://www.keil.com/support/docs/3250.htm
"if you want to be sure, you must generate a .bin file"
Not at all - the C51 tools tell you the image size directly!
"using 'fromelf'"
The C51 tools don't use ELF - so I doubt that 'fromelf' will help?
" if that one is smaller than the storing media, you are in business!"
Not quite - you need both the Code storage area and the data storage area to be of adequate size before the program will run correctly...
Andy, I have a terrible headache today - something made me see "ARM" toolchain instead of C51! I apologize to the OP.
so as said by per before that The flash memory is for code - the instructions telling the processor what to do.
The data memory (RAM) is for variables, i.e. letting the program keeping track of what it is doing.
can i select a UC with flash memory >= code size?? and please tell me what does data size represent.
The text "The flash memory is for code" should be read as "is intended for code". I also wrote that if "an array stores constant - unchanging - data, then you can move the array into the flash, i.e. among the code."
No, I don't think any manufacturer sells any processor with flash memory > code size. But the compiler does support placing read-only data into the code region, so it will be enough to have a processor with a flash size larger than what you need for the program code. The remaining region of the flash may then be used for constant data.
There are some 8051 chips that have a partially overlapping memory structure, where the application can reprogram the flash. This can allow the flash to be used for semi-static data - but the flash memory supports a limited number of write cycles, so the flash region can't be used instead of RAM.
I'm not sure what you mean with "what does data size represent". The processor may have more than one data region, in which case there may be more than one data size.
Oh yes they do!
The 8051 architecture limits the CODE size to 64K - but there are 8051-based chips available with >64K Flash (eg, SiLabs).
Depends on view. The 8051 chips with > 64kB flash has the flash mapped for CODE space. It's just that you will need banking or similar.
But have you seen any chip manufacturer selling a 8051 with flash for the RAM area - unless it has the overlapped CODE/XDATA regions I mentioned?
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