Posted on May 17, 2011 at 12:04phaze,
OHHH! Your map makes more sense now. I was assuming that your bootloader was located in secondary flash (csboot - common to all pages), and that your 64k main app was split between fs0 and fs1. I was going to ask how the hell you avoid using paging, but now I get it.
On a good note, I've managed to make my current version work. My bootloader is located in csboot0, and main app in fs0. I've had much difficulties w/ startup.a51. I cannot seem to use a string for my key2check because I have little knowlege of the assembler's rules. So Im simply checking one byte. I realize that this is risky for a release version, but for now, it'll work fine.
The SRAM reset issue was due the fact that I copied my startup.a51 template from another uPSD example which delcared XDATASTART & XDATALENGTH = 0x2000. As you mensioned, the startup init code 'IF XDATALENGTH <> 0'... was reseting my SRAM. I have corrected this issue.
Obviously, since my app now works, I have managed to locate both apps using ?C_C51STARTUP(0x0500). But I had issues locating statusbytes.
It seems that the strings within my app (which are also considered constant code space) always preceed my statusbytes.
EXAMPLE of main.c:
const code unsigned int statusbytes = (0xFFFF)
void main(void)
{
printf(''AAA'') //'A'=65=0x41
}
By reading the .hex file, my const code space is as follows
:1005F000414141FFFF....
Notice how the string preceeds the statusbytes.
So, if I alter my code, i run a high risk of moving my status byte location.
No need to respond to this issue. I just wanted to let ya know (FYI). I think that in our full implementation, instead of statusbytes, we are going to use a checksum over the entire main application to validate it. This is due to the fact that our device will be subject to a very rugged environment, physically and electrically, which could posibly corrupt flash.
I am currently testing using the uPSD3234A w/ 8Kb SRAM. We are going to use the PSD w/ 32Kb SRAM for our product. However, we need to extend this memory to 64K.
Have you any experience adding external RAM to these devices? If so, can you suggest a good chip select pin? Are there any address bus contensions that I must be aware of?
Thanks again for all of your help.
