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Xilinx OCM memory use limitations ?

Hi all,

We are building a very simple SOC ( PPC 405, internal memory, UART light) in a V4FX60, with a very simple firmware. The point is that when we use the PLB_BRAM memory, the GDB debugger works fine, but wneh we use the OCM memories, the debugger behaves in astrange way. When we download the file then it goes in a assembly state and executes nothing, I guess it went in some exceptions or executed some unexpected instructions.

Is there something to know to use the OCM memories ? Are there some configuration to make in EDK ?

Thanks for your help.

Stéphane.

Reply to
SJU
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in

tes

Hello Stephane. How do you write to the OCM Bram? i am using a VHDL file in the PORTB. probably i dont write in the correct location. But the simulation is strange to me also. Dont forget if you are using port B to set the clk to sys_clk_pin and the Reset to sys_bus_rst.

regards

Reply to
xenix

in

tes

What you need to watch out for is how you map the memory. One of the items we've noticed in previous builds was if the ISOCM and DSOCM were not in seperate 24M regions, then things would act funny. Therefore, we've mapped our ISOCM to 0xFFFFxxxx and our DSOCM to 0xFEFFxxxx. It seems to work fine in our builds so far. I have not tried re-tuning it yet since I haven't needed the OCM for my current system testing. Also, if you do have the memories separated, you may need to map in the ISOCM through the command line options of XMD: isocmStartAdr isocmSize.

-- Mike

Reply to
morphiend

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