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
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.
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).
I presume you mean:
"can I select a uC with flash memory >= my progran's code size?"
The answer should be obvious!
Think about it: If you buy a PC program that says it requires x MB RAM and y MB disk, can you use it on a PC that has more RAM and disk than that...?
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?
"can I select a uC with flash memory >= my progran's code size?" sorry if iam not clear with this statement here i mean to ask if it is sufficient to consider code size in the selection of UC without considering the XDATA size, as it was said befor that the XDATA has nothing to do with flash memory size and it looks for RAM.so i just wanted to confirm that point.
and in the statement "what does data size represent" i wanted to know what exactly it represents as when i compiled my code in keil i got as Program Size: data=9.0 xdata=6320 code=3632.
in the beginning i thought that i can use 89c51 for my code what ever i had, later on with all of ur advice i understood that i have to add an external RAM as my XDATA is large.later i was suggested to go for UC with larger flash memory as my HEX file size is around 12K. This is the reason i raised an issue of "can I select a uC with flash memory >= my progran's code size?"
Please tell me if that is sufficient and also about the data=9.0
The flash memory can not be used instead of RAM. It is intended for code but you can instruct the compiler to place constants there too. But it is a type of read-only memory, so if you need to be able to regularly change the value of a variable then you need to look at something else.
DATA in this situation is one of several memory areas in your processor. The different memory areas in the processor has different capabilities, and requires different ways to access them. The DATA area is a RAM area built into the 8051 chip. The XDATA is another memory area, originally intended for use with extermal memory chips and requiring different processor instructions to access the variables. The 8051 can have internal and/or external XDATA memory. The DATA area is extremely limited in size, but it is possible to have very large XDATA support. The instruction set is intended for accessing up to 64kB of XDATA, but it is possible to get past this limit. People who think that 64kB of XDATA is little should probably look at other processor architectures instead.
You can use the following link and search for 8051 chips with enough space for your program and for your variables. http://www.keil.com/dd/search_parm.asp
Note that the colum for RAM has the heading "DATA +XDATA", giving the built-in amount of RAM for these two memory areas.
For configurations that are seldom changed, but must be remembered after a power loss, you can look at the column "On-chip EEPROM". But you are limited to 100.000 to 1000.000 writes/memory cell for most EEPROM, so it is a complement, but not suitable to use instead of RAM.
Thanks PER for that information..
That means that your program uses 9 bytes of DATA space and 6320 bytes of XDATA space and 3632 bytes of CODE space.
Clearly, this means that your target system must provide at least 9 bytes of DATA space and at least 6320 bytes of XDATA space and at least 3632 bytes of CODE space. Whether these are provided internally on the chip, or with external chips on your board (or a combination of both) is really immaterial.
PS
If you're still not sure of the differences between DATA, CODE, and XDATA spaces, then you still haven't sufficiently studied the basics of the 8051 architecture - including the so-called "bible". See the links provided earlier.
look up those two