The Overlay mechanism implemented by Keil is ingenious. Moreover if we want add some functionnality in Eeprom without change ROM code is to my mind impossible because DATA GROUP area will be modified with new local variables used in our new functions in Eeprom. What do you think about this?
Thanks a lot,
Are the following guesses correct?
You currently have a system that has both rom and eeprom in it. The interrupt jmp table in eeprom. You currently have code the resides in both the rom and eeprom. You want to modify the eeprom part and leave the rom part alone.
I already generated ROM code and i would to use Eeprom memory to add some fucntionality but without any change of ROM code since it is already loaded. But when i add more than 1 local variable in my function the ROM code changed and cause problemes after link.
Split your Project into two.
One for your ROM and one for EEPROM.
After generating ROM-Project look the used resources in DATA, XDATA etc. These had to be excluded from EEPROM-Project.
And for using functions in EEPROM use adresstabel with entrypoints.
I am very confused. How can you extend the fuctionality of rom code without changing the rom?
One of the disgusting facts about the Keil software is that if you change the name of a variable (or add one) the whole DATA segment layout changes. Not using overlay is usually not an option. I sometimes work with software written by someone or another who uses variable names that are meaningless and in reforming such code I like to change the names and then compare the hex files to ensure that the namechange was the only change (I do make mistakes). This works fine for functions, but try it with a variable and booooooom, the whole hex file changes. As testing only guarantees the absence of KNOWN bugs, it takes an inordinate amount of time to verify what could be verified with a simple hex compare if the sequence of the variables were not shuffled.
It would make sense to order the variables by occurence rather than some random? order.
Daniel wrote that he had ROM and EEPROM. And he want to add some functionnality in Eeprom:
So i understand he will change the content of EEPROM. Physical by exchange or by in circuit programming.
By writing/generating code with uvision he need to split his project. One for target ROM and one for target EEPROM.
And when he calls function in EEPROM the ROMcode need the locations of EEPROM function. And this can be done tables with function entry points.
This is what i have done in an project with Bootloader and reprogrammable Applikation.
If you want no sorted variables use NOSO (no sort) as directive for the Linker.
This is not documented but comes as info directly from Keil.
*<|:-), merry xmas
The NOSO (short for NOSORTSIZE) is documented on p316 in the current Linker manual (07.2000)
But this relates to the ordering of Segments - not variables.
NOSORTSIZE has been available for a long time (since Version 5.50).
We continually add new features to the Keil tools. This means that features are added each week or month--not just once every year or two so we can sell upgrades. With this continual development comes New Features. Unfortunately, we cannot reprint manuals each month or two. We also cannot send new printed manuals to customers who download updates. So, we added a file of Release Notes to each installation.
The NOSORTSIZE linker directive has been documented in the release notes since it was introduced.
Refer to the following knowledgebase article for the C51 V6.00 release notes.
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