Hi,
I'd recommend you focus your efforts on milkymist-ng
(https://github.com/milkymist/milkymist-ng /
http://milkymist.org/3/migen.html). Since PSRAM is slow, I don't think
you could go much further than CPU + framebuffer - both are working
today on -ng.
Sébastien
On 02/08/2013 09:43 PM, Fernand LONE SANG wrote:
Hi folks,
In my spare time, I am trying to port Milkymist SoC on the Digilent
Nexys 3 board. Unfortunately,
this development board does not support DRAM and has a Cellular RAM
instead. I am currently
developing a module to drive this Cellular RAM and I am facing to some
issues. I wish someone
on this mailing-list could give me some hint to solve them.
On the Nexys 3 board, both norflash and Cellular RAM are connected to
a common bidirectional
data bus. Data are forwarded either to the norflash or the Cellular
RAM by selecting the right chip
using a chip select signal. To multiplex signal coming from the module
driving the norflash and the
module driving the Cellular RAM, I have coded a small bus "switch".
The code is attached to this
mail. Please note that I am using inout ports on the module.
After I run XST, and when I open the ChipscopePro inserter, I see that
XST has removed the
module that drives the norflash, the Cellular RAM and the bus
"switch". I have these warnings:
WARNING:Xst:2042 - Unit [...] : [x] internal tristates are replaced by
logic (pull-up yes)
WARNING:Xst:1906 - Unit [...] is merged (output ports from interface
drive multi-sources)
This topic has been discussed few years ago on Xilinx forum
(http://forums.xilinx.com/t5/Synthesis/problem-of-quot-INOUT-quot-use-quot-internal-tristates-are/td-p/122342)
and last year on Milkymist IRC channel
(http://en.qi-hardware.com/mmlogs/milkymist_2012-02-01.log.html)
and it seems that a solution to my problem is to change each inout
port, except ports from the top
module, to three equivalent signals (in, out, oe), right ? As I want
to keep my code for the Nexys 3
as close as possible to the code of Milkymist, so I wish someone
could suggest me a solution
(if an alternative exists) in which I do not have to modify the code
of the norflash core in Milkymist
to have the data port (inout) modified to its two equivalent signals
(oe is already available).
Any hint on how i can achieve this ?
Thanks,
--
Fernand
_______________________________________________
http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org
IRC: #milkymist@Freenode
