Spartan3AN DDR2 - bad writing zeros

Tue Mar 09, 2010 9:04 pm   

I've got a problem with my DDR2 (MT47H32M16) on my Spartan3AN board. I
use MIG 2.3 controler. The burst lenght is 4. When I'm writing the
data like x"A1A1B2B2" or x"01010101" everything works. I'm reading the
data after data_valid is set and writing to internal registers. Then
I'm sending it to RS232.

Problem is when I want write data with zeros... like x"A100B2B2" or
x"01010001". Then data which I'm reading are wrong. For x"A100B2B2" A1
I can read but else data are wrong:/

I'm little confused why it happens..

Tue Mar 09, 2010 10:59 pm   

On Mar 9, 2:04 pm, lusch <lukaszschodow...@gmail.com> wrote:

My guess is that it's the RS-232 link dropping your zeroes, not
the memory controller. It's standard practice on serial links
to treat null characters (x"00") as nothing, and therefore drop
them. Make sure the software at the other end of your RS-232
link is set up to receive binary mode rather than ASCII text.

Regards,
Gabor

Wed Mar 10, 2010 1:59 am   

On 9 Mar, 21:59, Gabor <ga...@alacron.com> wrote:


I receive data in serial terminal and I set hexadecimal rather than
ASCII so I see exactly byte to byte what I receive.

Thanks for replay.
Regards

Wed Mar 10, 2010 11:11 am   

Is this a custom board or a 3rd party eval board?

How confident are you about the terminations between the FPGA and memory?

What exactly do you get back when you write x"A100B2B2"?

What do you get back if you write all zeros?

Can you slow the transfer down (half speed?).

I'd be worried about signal integrity, but then the x"01010101" case would
suggest this might not be a problem. ?


Sounds like you're confident about the RS232 connection, if you weren't this
is the sort of thing my 1Pin Interface is useful for.

http://www.1pin-interface.com :-)




Nial

Wed Mar 10, 2010 11:35 pm   

lusch <lukaszschodowski_at_gmail.com> wrote:


Probably a getchar() / C style strings problem.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico_at_nctdevpuntnl (punt=.)
--------------------------------------------------------------

Thu Mar 11, 2010 12:22 am   

Yes, the problem was in RS232 Actually I don't know why.
I wrote simple module to write data to RS232 from FPGA and problem
appeared when I'd like send "00"

Thanks for cooperation
Luka

Thu Mar 11, 2010 1:06 am   

On Mar 10, 2:22 pm, lusch <lukaszschodow...@gmail.com> wrote:

I think previously you said that you were using a displaying the
result in HEX in your terminal program. Gabor pointed out that RS-232
would ignore 00 unless you were in binary (vs ascii) mode. Your reply
here wasn't

The value 00 is the same as 0 which is also NULL or end-of-string in C
software. You haven't said how the value is sent to the RS-232 port,
but if you were using MicroBlaze and printf think that this could be
getting swallowed by the software routine.

In order to separate the issue between the Memory read/write and the
RS-232 transmit. I would suggest that you change your design to
simple write a number of zero and non-zero values to the RS-232 and
see if these appear correctly in your RS-232 terminal.

Ed McGettigan
--
Xilinx Inc.

Thu Mar 11, 2010 11:36 am   

"lusch" <lukaszschodowski_at_gmail.com> wrote in message
news:9b933786-e1b2-4648-bdd4-1df24785efcd_at_33g2000yqj.googlegroups.com...

A haaa, so the 1 Pin Interface would have been invaluable, how many hours
did you waste? (Without giving it too hard a sell).


At least the problem isn't FPGA or PCB based!



Nial.