OMAP L138 Internal Memory / DDR Data Space

Jaime Ferra

Other Parts Discussed in Thread: OMAPL138

Hi,

I'm currently working on a project for which we use the OMAPL138 processor in the design. TI'm seeking some help to understand how many internal memory spaces there are available on the chip and especifically how the DDR2 Data sector (See attachment from OMAPL138 data sheet) is used by the processor. Are the 512MB of DDR Data available for external data storage or are those used internally by the processor for DDR memory controller? The documentation that I've seen talks about the mDDR/DDR2 controller but it doesn't mention the purpose of the DDR2 Data space. Is it necessary to have an external DDR memory connected to be able to use the 512 MB memory space?

Thanks,

Jaime

over 12 years ago

0 David (ASIC) Liu over 12 years ago

TI__Guru**** 158306 points

Jaime

DDR2/mDDR memory controller has:
– 16-bit DDR2 with up to 512-MB memory address space
– 16-bit mDDR with up to 256-MB memory address space

So you need to have external memory to use the 512MB memory address space.

Thanks
David

0 Jaime Ferra over 12 years ago in reply to David (ASIC) Liu

Prodigy 50 points

David,

Thanks! So that means that pretty much the DDR Data sector on the memory map is used just by the DDR2 controller. Just curiosity I ran a memory test which writes and reads a value to DDR2 Data memory sectors (0xC000 0000 - 0xDFFF FFFF). Wouldn't just be possible to do the same using that internal space instead of adding an external memory? Is there a specific reason for not being able of using that internal space?

Once again,

Thanks!

0 Mukul Bhatnagar over 12 years ago in reply to Jaime Ferra

TI__Guru* 81755 points

Please see the following posts on the same topic

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/207300.aspx

Essentially only 256MB is usable from the memory map on the chip for DDR2/mDDR memory given the total address lines available and the memory densities availalbe in the market.

Regards

Mukul

0 Jaime Ferra over 12 years ago in reply to Mukul Bhatnagar

Prodigy 50 points

Hi Mukul,

Thanks for answering! Still, I'm looking for the reason of why the DDR2 Data memory sectors could not be used as normal memory spaces without having to actually connect an external DDR memory? I'd run some of the starterware examples using the OMAPL138EVM and it allocates the program data within the DDR2 data memory sectors.

Thanks,

Jaime

0 Mukul Bhatnagar over 12 years ago in reply to Jaime Ferra

TI__Guru* 81755 points

Jamie

This portion of the memory map is for "off chip memory" , you do not have anything on it, unless you actually hook up an external memory. So you can only allocate and use whatever is the density of the DDR2/mDDR memory you hook up to the processor.

Regards

Mukul

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OMAP L138 Internal Memory / DDR Data Space