Forgive my ignorance; I've never used pre-made bitstreams before, and
certainly have never used Vivado before either. But, in my (limited!)
experience, a bitstream is the **final** result of the synthesis
process. As far as I know, once you have a bitstream, the most you
can do is change the contents of block RAM; the digital logic itself
will be frozen.
Can a tool like Vivado allow you to "bolt on" to a pre-existing
bitstream, so as to include your own memory controllers and the like?
(Feel free to answer off-list if you want; I recognize this is
off-topic.)
If not, it seems like the bitstream you get is fixed function, and
should already include a memory controller if it's been configured to
grant access to DDR RAM.
Thanks for clarifications from Vivado users.
On Wed, Aug 29, 2018 at 5:25 PM Bruce Hoult <
bruce...@sifive.com> wrote:
>
> I'm pretty sure the answer is that E31/E51 bitstreams for the Arty are intended as evaluation for the corresponding cores in microcontroller SoCs, and so have just the 16 - 64 KB of scratchpad SRAM they will have in an SoC (and which is provided within the FPGA on the Arty).
>
> Vivado comes with a DDR controller intended for use with their Microblaze core. I don't actually know whether the license allows it to be used with other soft cores, though probably someone skilled with FPGAs could physically make it work.
>
> On Wed, Aug 29, 2018 at 10:09 AM, Tommy Murphy <
tommy_...@hotmail.com> wrote:
>>
>> Have you checked the SiFive forums in case this is answered there?
>>
>>
https://forums.sifive.com/
>>
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