SAM3U4E with external SRAM

Discussion around product based on ARM Cortex M3 core.

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marioR
Posts: 7
Joined: Sat Feb 18, 2012 2:21 am

SAM3U4E with external SRAM

Sun Feb 19, 2012 7:37 pm

Hello gentlemen,

I have a question regarding the connections. I have a 61LV256 (http://www.issi.com/pdf/61LV25616AL.pdf) 4 Meg SRAM chip. After studying the recommended settings found on the SAM3U4E datasheet (http://www.atmel.com/Images/doc6430.pdf, pg 356), I couldn't find pins for "UB" and "LB".

Where can I connect these two pins ?

Also, can some one let me know if the following is correct?

Code: Select all

61LV256   ----->       SAM3U
A0-A17 	----->       A0-A17
I/O0-I/O15	----->       D0-D15
CE		----->       NCS0
OE		----->       NRD
WE		----->       NWR0/NWE






LB, UB on 61LV256? grounded, shorted?

Thank you,
Mario
incognito
Posts: 32
Joined: Tue Jul 13, 2010 12:54 pm

Re: SAM3U4E with external SRAM

Sun Feb 19, 2012 10:10 pm

The info you want is on page 358 of the SAM3U data sheet

A0/NBS0 - Address Bit 0/Byte 0 Select Signal
NWR1/NBS1 - Write 1/Byte 1 Select Signal

Memory Connection for a 16-bit Data Bus

SAM3U -> 61LV256
D[15:0] -> D[15:0]
A[19:2] - > A[18:1]
A1 -> A[0]

NBS0 -> LB
NBS1 -> UB

NWE -> Write Enable
NRD -> Output Enable
NCS -> Memory Enable
CptTitanic
Posts: 871
Joined: Sat Oct 30, 2010 6:04 pm

Re: SAM3U4E with external SRAM

Sun Feb 19, 2012 10:14 pm

You need to handle byte lanes, A0 becomes NBS0

You do not direct map A0..A17 because the memory is 16-bit wide, A1..A18 of the ATMEL part needs to go to A0..A17 of the SRAM
marioR
Posts: 7
Joined: Sat Feb 18, 2012 2:21 am

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 1:02 am

Thank you for all the hints. After your suggestions, I made the following corrections (also on pg 355 of Datasheet):

SAM3U -----> 61LV256
------------------------------------
A2-A18 -----> A1-A17
D0-D15 -----> I/O0-I/O15
A1 -----> A0
NBS0/A0 -----> LB
NBS1/NWR1----> HB
NWR0/NWE -----> Write Enable
NRD -----> Output Enable
NCS0 -----> Chip Select


I only have one shot at this (working with BGA package), so can some one please advice corrections. My main concern is the connection of the memory address lines A1-A17

1) 61LV256 does not have A18 connection!
I counted up to A17 (not A18!) to connect to the A2-A18 (on SAM3U), since 61LV256 does not have a physical A18 connection

2)NCS0 connected to CE

THANK YOU !!!
incognito
Posts: 32
Joined: Tue Jul 13, 2010 12:54 pm

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 9:04 am

Don't worry about A18 connection if the RAM doesn't have A18.

If it was a bigger SRAM, it would have more Address lines to address the available memory.

It is only 4Mbit, arranged as 256k(11 1111 1111 1111 1111) 16bit words. Thus it needs only A0 - A17 to select the correct address, and the upper and lower byte select to be able to select the upper or lower byte of the 16-bit value at the corresponding address.

Make sure you set up your processor pins accordingly in the SAM3 software.
marioR
Posts: 7
Joined: Sat Feb 18, 2012 2:21 am

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 5:42 pm

Thank you for your help.

Unfortunately, I won't know for a while since I have not even drawn up the board yet.

Right now, I'm figuring out how to get everything connected.

When you suggest setting up the software correctly in software, do you have a reference to recommend?

I will be using avr-gcc + AVR Studio 5.
gerhardf
Posts: 554
Joined: Thu Dec 02, 2004 2:28 pm

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 9:19 pm

marioR wrote: I will be using avr-gcc + AVR Studio 5.
avr-gcc and avr-studio will not work for sam3.

regards
gerhard
marioR
Posts: 7
Joined: Sat Feb 18, 2012 2:21 am

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 10:31 pm

Are you serious ?!?!

Certainly you are not implying AVR32 Studio 32? I thought Atmel merged AVR Studio 32 into Studio 5?

I was hoping to use Jtagice MKII and AVS5 yo program my board
CptTitanic
Posts: 871
Joined: Sat Oct 30, 2010 6:04 pm

Re: SAM3U4E with external SRAM

Mon Feb 20, 2012 10:46 pm

He's serious, the SAM3U4E is an ARM device. You will need Keil, IAR or Rowley type development tools, or ARM GNU-GCC (WinARM, Yagarto)

ARM != AVR, AVR is an ATMEL specific architecture. The Cortex-M3 is an ARM device running Thumb2 16-bit instructions only.

For JTAG you'll need a SAM-ICE (Segger J-Link), or for Keil you could use a U-Link.
marioR
Posts: 7
Joined: Sat Feb 18, 2012 2:21 am

Re: SAM3U4E with external SRAM

Tue Feb 21, 2012 12:08 am

CptTitanic wrote:He's serious, the SAM3U4E is an ARM device. You will need Keil, IAR or Rowley type development tools, or ARM GNU-GCC (WinARM, Yagarto)

ARM != AVR, AVR is an ATMEL specific architecture. The Cortex-M3 is an ARM device running Thumb2 16-bit instructions only.

For JTAG you'll need a SAM-ICE (Segger J-Link), or for Keil you could use a U-Link.
When I bought my JtagIce MKII, I remember reading it having support for the ARM platform. And after going over some docs, I see support for AVR32, which is not ARM.

Wow, what a surprise.

It looks like I need more research before even starting.
Bob_Keil
Posts: 24
Joined: Mon Mar 28, 2011 7:10 pm

Re: SAM3U4E with external SRAM

Tue Feb 21, 2012 12:12 am

Hello

Keil uVision will work with SAM-ICE and Segger J-Link (black one) as well as ULINK2 or ULINKpro.
Serial Wire Viewer is supported with all.
Keil uVision has many examples for the SAM3U.

I soon have labs for SAM3S, SAM3X and SAM4S.

Bob Boys
ARM

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