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code working in simulator but not when burnt.

deepthi narahari

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

Parents
  • 0 in reply to deepthi narahari

    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.

Reply
  • 0 in reply to deepthi narahari

    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.

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