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In the "options for target" dialog box on the "Target" tab (uVision IDE) there is a check box called "Use On-chip XRAM...". When looking at the help file for this it says:
Use On-chip XRAM (0x0-0x2FF) Specifies the usage of the on-chip components that are typically enabled in the CPU startup code. If you are using on-chip xdata ram (XRAM) you should also enable the XRAM access in the startup file.
This sounds to me like I need to check this box and modify the 'start900.A51' startup file to get the on chip xdata to work. Is my assumption correct? What exactly does 'Checking' this box do?
Is my assumption correct? yes as far as startup goes. What exactly does 'Checking' this box do? have no idea - I do not use the IDE and do not do anything beyond "modify the 'start900.A51' startup file "
Erik
"Is my assumption correct?"
Yes, it is.
"What exactly does 'Checking' this box do?"
It's really just informing the tools about the amount of XRAM available in your target - so that the tools, in turn, can warn you if you exceed that amount. It also lets the tools allocate addresse in the appropriate range(s).
Probably a more accurate and useful name for the checkbox would be, "Assume that the size of XRAM specified for this chip in the Device Database is available for use".
This has been discussed a number of times before...
http://www.keil.com/forum/docs/thread5653.asp http://www.keil.com/forum/docs/thread4241.asp
Thanks for the quick responses
I have another questions: Are there any side effects with not setting the XDATA length in the startup file (other then the variables initially having bad/random data)?
other then the variables initially having bad/random data no, not for compile and link, There may be something with the simulator if you use that which I do not.