von Enrique (Guest)

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Hello everbody,

I am in a very big project with an ALTERA FGPA Cyclone IV. This FPGA is 
going to control several systems and every  system has its own 
configuration file sent by SPI protocol  which it is already implemented 
like a VHDL module in the FPGA. In the start up of the system, the FPGA 
is sending the intial configuration file for a default hardware which is 
the most commun. This configuration file is stored in a FIFO memory with 
the possibility to be modified "on fly" thanks to the "IN SYSTEM MEMORY 
CONTER EDITOR" tool provided by Quartus II SW. So if the Hardware 
changed we can use this tool to change the initial configuration SPI 

But we don't want to use this tool and we want to change the initial SPI 
config file in the FIFO using the a command recevied by ethernet protcol 
(The FPGA has also implemented a Ethernet module to communicate with a 
PC). This command is going to be read by the FGPA and accordint to this 
we will change the initial configuration file.

See below the instantation of the FIFO memory:

    generic map (
      DATA_SIZE => SPI_MEM_RDOUT'length,
      INIT_FILE => "../fit/SPI_INIT_RAM.mif",
      INST_NAME => "SPIF"
    port map (
      clock    => CLK            ,
      wren      => '0',
      address => SPI_MEM_ADDR,
      data      => (others => '0'),
      q        => SPI_MEM_RDOUT

As you can see there is a GENERIC ==> "INIT_FILE" where you have to 
indicated the path of the file you want to load. And it is this path 
what I want to modify "on fly" when I receive the ethernet command...

Any idea how to implement this?


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von Roger S. (edge)

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What you’ve got here is a plain RAM, not a FIFO.

The INIT_FILE generic is evaluated during synthesis/assembly at design 
compile time.
The purpose of this is that the memory in question is initialized after 
FPGA configuration with what the initialization file described at 
compile time.

By using the ‘In Memory Content Editor’ you are able to update the RAM 
contents at runtime.

Obviously the configuration bitstream is not affected, meaning that when 
you reconfigure the FPGA, the RAM will hold its original contents.

To update the RAM contents via Ethernet, all you have to do is to 
provide a write port for the Ethernet module.
This is the same concept as how the ‘In Memory Content Editor’ is 
updating the RAM behind the scenes.

It looks like the RAM is a generated IP, so you can add this port by 
using the wizard.

Cheers, Roger

von Enrique (Guest)

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Hi!!! Thank zou vey much for your answer, Yes I can provde a write port 
to the RAM memory but then I observe the next problem: When I  power 
off/on the system, the RAM will load the init file indicated in the 
generic. And what I would like to keep the last file loaded. Is there 
any other possible solution for this?


von Roger S. (edge)

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How is your FPGA being configured?
If it’s Active Serial trough an EPCS device, you could use an empty 
sector as nonvolatile storage.

Cheers, Roger

von Enrique (Guest)

Attached files:

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Hello Roger, Thanks again for your answer. See the picture attached to 
take a look to the connection between the FPGA and the flash. I guess 
that I can do what you are indicatind "use an empty sector as 
non-volatile". But Could you explain in detail how to get this? Or How 
can I search this in internet?


von Roger S. (edge)

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The Flash is accessible from user logic. So all you need is the S25FL064 
datasheet and have a look at the instructions: READ, RDSR, WREN, SE, PP

You can read a configuration in one go with READ.
To update a configuration you’ll have to erase the sector (SE) and write 
the data with one or more page program (PP)
All modifying instructions require a write enable (WREN) upfront.
Erase/program completion can be checked with read status register 

However, your circuit connects the Flash in Quad mode to the FPGA.
AFAIK none of the Altera stuff Is making use of this.
Which suggests that you might have something in your design that
Already connects to the Flash, especially since the Flash is quite big 
compared to the bitstream size.
In that case you might want to team up with the solution in place.

Cheers, Roger

von Enrique (Guest)

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ok I will try it and I will tell you how it was....

Thank u very much!

von Enrique (Guest)

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But I don¨t know how to access to the flash from the FPGA? Can I do it 
with the currento flash configuration?? Is there any Altera IP 
Megawizard function to make everything easier??


von Roger S. (edge)

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Your Flash configuration is fine. There are two suitable IP for this:

-  EPCS Serial Flash Controller
-  Avalon Serial Peripheral Interface

Both of them are Avalon/Qsys IP and only take care of the SPI 
serialization/deserialization part.
Formulating Flash commands, programming/erasing etc. is not abstracted 
with this.
Altera provides a software driver for that but nothing in HDL.

Anyways, you can use almost any SPI IP or roll your own, this is super 
simple stuff.
As for the Flash commands, I doubt that you’ll find something ready-made 
that fits your needs.

Cheers, Roger


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