Re: external sdram and gdb tool

Hi Tom,

How are you populating the SDRAM with your .elf file when not using the 
debugger? Perhaps you're doing this properly, but you didn't mention it 
here so I have to ask.  When downloading the .bit file via iMPACT, the 
only .elf data that you can possibly have is that in the Block RAM.  If 
you're not moving the .elf into SDRAM then that's the problem; you will 
need a bootloader of some sort to move the data from a static location 
(Flash, etc.) into SDRAM.

If you are already loading the .elf into SDRAM, then use the XMD tool to 
check the validity of the .elf file in memory.  What I typically do is 
run an object dump (either mb-objdump or powerpc-eabi-objdump) on the 
.elf file (I typically use the -S option) and pipe that out to a text 
file.  Next, connect to the device via XMD (ppcconnect or mbconnect) and 
do mwr's from the base address of your SDRAM.  If you do something like 
mwr 0xF0000000 20, it will dump the 20 addresses after 0xF0000000 
(obviously change this to match your SDRAM base address) and you can 
check them against the .elf file.  The boot section of the .elf is at 
the bottom of the file so look there to start.  This will check that 
your bootloader is doing its job properly and that your system is able 
to read from the static location (Flash, etc.) properly (we already know 
that it can write to SDRAM properly because it works with the debugger).

I hope this information helps.  If not, please post a follow up or open 
a case with Support.


Ryan Laity
Xilinx Applications


Tom wrote:

> Hi, 
>
> I have some project where I store my entire program in the external
> sdram (by redirecting every section in the linker script to the
> sdram). When I download the program to the board, it doesn't work.
> When I run the program in the debugger tool, it works. Does anybody
> know an answer to this problem ?
>
> regards, 
>
> Tom