Which RAM chip to use for EBI and how to connect?

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Who has experience with using external RAM with ATXMEGA128A1?

I'm looking for a 16MB RAM chip, but I don't know should it be SRAM or SDRAM or whatRAM and how it should be connected (by hardware and software).

Does someone know for a working RAM chip that I can buy from eBay and that a regular PCB industry can get and the schematics of connecting that specific one?

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The Xmega128-A1 Xplained has a 64Mbit SDRAM chip on it.  You can download the schematic from the Atmel website.  There is a quickstart/example project that covers configuring the EBI to talk to the chip.  The EBI on the Xmega series only support a 4-bit data bus.  You have to move up to the 32-bit UC3 chips to get an EBI with a 16-bit data bus.

Greg Muth

Portland, OR, US

Xplained/Pro/Mini Boards mostly

 

Make Xmega Great Again!

 

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8-bit SDRAM was added to XMEGA AU.

Some 8bit SDR SDRAM though more likely to have 16bit SDR SDRAM in-stock and at a lesser price.

Schematics :


 Atmel Corporation

http://www.atmel.com/Images/Atmel-8331-8-and-16-bit-AVR-Microcontroller-XMEGA-AU_Manual.pdf

(page 325)

When four EBI ports are available, SDRAM can be connected with a three-port or four-port EBI configuration.

When a four-port configuration is used, an eight-bit data bus is available, and all four chip selects will be available.

 Atmel Corporation

http://www.atmel.com/images/Atmel-8385-8-and-16-bit-AVR-Microcontroller-ATxmega64A1U-ATxmega128A1U_datasheet.pdf

(page 48)

4- or 8-bit SDRAM with 4-port EBI configuration

https://www.avrfreaks.net/forum/ebi-4-port-sram-mode-sram-512k-sram-2m-correct-connection-xmega 

"Dare to be naïve." - Buckminster Fuller

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Now I'm confused. I don't know do I have an XMEGA AU or an XMEGA A. On the XAVRB's board ( http://www.alvidi.de/products/EN...), the top of the chip says

ATXMEGA128A1

AU 1105

While on my Ready for XMEGA board, the chip says

ATXMEGA128A1

AU 1310

Because of "AU", it could be an ATXMEGA128A1U, but on the MikroElektronika website, it said it's an ATXMEGA128A1 without an U. So which XMEGA do I have?

According to the one which I have, shall I use the 4-bit data bus RAM chip or 8-bit data bus RAM chip? These RAM chips probably have some full name like 128Mbit SDRAM and some parameters that are visible on the title. So can you tell me what I should be looking for exactly so that I don't get an incompatible chip?

 

And for some reason, I can't find a 16MB (128Mbit) RAM chip either in SMD form, in DIP package or on a breakout board.

I need all of the 16MB for my project. (Don't tell me to move to ARM. I'm trying to make an 8-bit device with most RAM as possible). I need the RAM first in DIP package or a breakout board before making the PCB so I can experiment with it and then in the final product, an SMD formed RAM must have the same pinout of the connection with XMEGA just like with the first RAM so that my source files work correctly.

Can someone find one for me? I seriously don't know why I'm getting results of serial RAM chips or ARM chips instead of just a simple RAM chip that is compatible with XMEGA.

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The AU in those is simply the package designation. The chip you have appears to be the old, buggy and now discontinued/replaced 128A1

 

In future buy eval boards from Atmel - they're pretty much guaranteed only to stock current (bug fixed) CPUs.

EDIT: But just a minute - while the link you gave gives a 404 Not Found error. The XAVRB V2.0 appears to be this:

 

http://www.alvidi.de/products/EN...

 

That page makes the point of it being  ATxmega128A1U-AU The first U in that is the important one meaning "USB". The "AU" on the end is, again, a package designation.

 

If it is that board the schematic is here:

 

http://www.alvidi.de/data_sheets...

 

The MT48LC16M4A2 in that is a 64Mb SDRAM (that is 8MB).

 

If the board really does have an SDRAM (the photo certainly seems to show one - the second largest package on the PCB) it kind of raises the question as to why you are asking about devices for EBI in the first place?

Last Edited: Mon. Jun 22, 2015 - 04:29 PM
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Alright, so I should get that board. But it has only 16MHz crystal. I need 32MHz. Is it somehow possible to connect the 32MHz crystal if I buy it?

 

About the question, the device with EBI is for project that I don't want to talk about yet. All I want is to get the most RAM out of XMEGA. There surely needs to be a 16MB chip for XMEGA.

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Foxcat385 wrote:
And for some reason, I can't find a 16MB (128Mbit) RAM chip either in SMD form, in DIP package or on a breakout board.
Appears that Alliance Memory is producing a possibly discontinued Micron SDR SDRAM; it's 64Mx8 so tie the unused address bits.

Digi-Key usually has more RAM chips than some distributors; the whopper URL :

http://www.digikey.com/product-search/en?pv142=131&pv142=132&pv142=136&FV=fff40027%2Cfff80434%2C2540016%2C254006c%2Cf040006&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

The in-stock part (industrial temperature range, TSOP) from above URL :

http://www.digikey.com/product-detail/en/MT48LC64M8A2P-75%20IT:C/1450-1248-ND/5155736

 

As a counter, another major US distributor is Mouser and appears to be ISSI there; fyi, ISSI was recently acquired by Microchip.

http://www.mouser.com/Semiconductors/Integrated-Circuits-ICs/Memory/DRAM/_/N-98x2d?P=1yzonphZ1z0wad3

 

TSOP - popular package and straight-forward to design a PCB to use that package; otherwise, likely that a TSOP-to-DIP adaptor PCB exists.

BGA - don't fear because there are BGA adaptors and the SDRAM BGA pitch is achievable with a relatively inexpensive 4 layer PCB.

Usually quick to go immediately to a custom PCB and quicker to modify/patch/hack an off-the-shelf development board for proof-of-concept and maybe first prototype.

"Dare to be naïve." - Buckminster Fuller

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Oh my! That shipping is so expensive! €90! How come? That PCB will be so expensive. Unless the PCB company has good shipping. What do you think what will happen with the price if I'm getting a PCB from a company to who I give my documentation? Is it usually expensive or do they have ways around to make the shipping cheaper?

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Alright, so I should get that board. But it has only 16MHz crystal. I need 32MHz.

 

You can use the PLL in the A1U to double the 16MHz XTAL to 32MHz, but what you should really do is quadruple to 64MHz because the EBI can be clocked at that speed.  Set prescaler C to divide by two so FCPU and FPER will be 32MHz, while FPER2, the one that clocks the EBI, will be 64MHz.

 

Greg Muth

Portland, OR, US

Xplained/Pro/Mini Boards mostly

 

Make Xmega Great Again!

 

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In the documentation of the SDRAM chip IS42S16800A http://www.issi.com/WW/pdf/42S16... on page 16, it says that the operating frequency is 143MHz if "-7" something and 100MHz if "-10." something.

An XMEGA that works at 32MHz needs 64MHz SDRAM clocking.

Can the SDRAM be underclocked from 143MHz and/or 100MHz to 64MHz?

And what do those "-7" and "-10." mean?

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What does -7 and -10 mean? It's detailed on the first page.

There is no minimum to the clock speed, but you need to refresh the chip in adequate time, so that implies a minimum clock speed.