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TMS320F28388D: Selecting External RAM for the TMS320F28388D

Deci10
Prodigy 70 points

Part Number: TMS320F28388D

Tool/software:

Hi,

We are developing a board with the TMS320F28388D and are selecting external RAM. 

It looks like we need to use the EMIF1 interface with a 32-bit data bus width and 22-bit address lines to address 16 Mbit or more of external RAM.
We also have a high throughput requirement of 70Mbytes/sec for both read and write.

I found this article in the C2000 real-time controlled C28x academy that discusses the maximum throughput of the EMIF1 interface.

https://dev.ti.com/tirex/explore/node?node=A__AfcnE1gJNndsjeobl17Grw__C28X-ACADEMY__1sbHxUB__LATEST

In the article the ASRAM and DRAM speeds are given for EMIF interface. I pasted them below for convenience and added the throughput in MBytes/sec in the last columns.

Mem Type Max Clock (MHz) Access Type CPU Cycles Throughput (MWords/sec) Throughput assuming 16-bit word/access (MBytes/sec) Throughput assuming 32-bit word/access (MBytes/sec)
ASRAM 200 Read 9 22 44 88
ASRAM 200 Write 5 40 80 160
SDRAM 100 Read 14 14.2 28.4 56.8
SDRAM 100 Write 9 22.2 44.4 88.8

Q1: Is the above table correct for the TMS320F28388D and is my analysis correct that to achieve >70Mbytes/sec we need to use an ASRAM chip (with <=10nsec access time) connected to EMIF1 (12-bit addressing and 32-bit data configuration)?

 If yes, do you have an application note, example or development/eval board with the TMS320F2838x (or similar device) with external ASRAM that we can follow for our design (and potentially buy for prototyping) ?

Q1: SDRAM is easier to find (better availability) so it would be easier to buy a fast (>=166MHz SDRAM chip). Is the SDRAM clock speed  still limited to 100MHz on the TMS320F28388D and read throughput limited to 56.8MBytes/sec?
If SDRAM clock or throughput have improved we may be able to consider SDRAM.

Thanks in advance!




  • 0
    TI__Mastermind 24121 points

    Hi Mitch,

    Deci10 said:
    Q1: Is the above table correct for the TMS320F28388D and is my analysis correct that to achieve >70Mbytes/sec we need to use an ASRAM chip (with <=10nsec access time) connected to EMIF1 (12-bit addressing and 32-bit data configuration)?

    You can look at more detailed benchmarking with our EMIF design guide www.ti.com/lit/pdf/sprac96 which is created using the F2837xD family of devices, but F2838x has virtually the same EMIF module so the benchmarking is comparable. The findings are generally correct though the throughput is also dependent on the block size as observed in our testing.

    Deci10 said:
     If yes, do you have an application note, example or development/eval board with the TMS320F2838x (or similar device) with external ASRAM that we can follow for our design (and potentially buy for prototyping) ?

    The application note I provided can be used, though we currently don't have any publicly orderable hardware that really showcases the EMIF peripheral design. We have the design files for an EMIF extension board available at \boards\TIDesigns\F28379D_EMIF_DC . This is not orderable, but you should be able to leverage the board files to fabricate the board separately and then interface with our F2838x evaluation modules

    Deci10 said:
    Q1: SDRAM is easier to find (better availability) so it would be easier to buy a fast (>=166MHz SDRAM chip). Is the SDRAM clock speed  still limited to 100MHz on the TMS320F28388D and read throughput limited to 56.8MBytes/sec?

    Yes EMIF clock must be SYSCLK/2 for synchronous operation so 100 MHz.

    Regards,

    Peter