Hi, to ease the routing of my PCB, I'd like to swap some data lines on a SDRAM. I'd like to be 100% sure that the swapping will not create problems once the PCB is built. I use a SDRAM MT48LC8M16A2 from Micron. The only documentation that I found is: http://www.freescale.com/files/32bit/doc/app_note/AN2582.pdf about DDR, and they say "Pin-swap within a given byte lane to optimize the data bus routes further. Caution: Do not swap individual data bits across different byte lanes." Is there any other recommendation ? Any positive experience ? Thanks
pin swap in SDRAM
Started by ●January 30, 2007
Reply by ●January 30, 20072007-01-30
On Jan 30, 8:59 am, "tullio.grassi" <tullio.gra...@gmail.com> wrote:> I'd like to be 100% sure that the swapping will not create problems > once the PCB is built.The datasheet's advice is good. Swap within bytelanes as you wish. Do not swap between bytelanes. What further information do you need?
Reply by ●January 30, 20072007-01-30
larwe ha scritto:> On Jan 30, 8:59 am, "tullio.grassi" <tullio.gra...@gmail.com> wrote: > > > I'd like to be 100% sure that the swapping will not create problems > > once the PCB is built. > > The datasheet's advice is good. Swap within bytelanes as you wish. Do > not swap between bytelanes. What further information do you need?I am trying to understand if there is any side-effect of pin-swapping. As an example, I was thinking to pin swap data lines of a Flash memory; but I realized that these devices have special commands sent on the data bus, so commands would get screwed-up (and myself too :)
Reply by ●January 30, 20072007-01-30
larwe <zwsdotcom@gmail.com> wrote:> > > On Jan 30, 8:59 am, "tullio.grassi" <tullio.gra...@gmail.com> wrote: > >> I'd like to be 100% sure that the swapping will not create problems >> once the PCB is built. > > The datasheet's advice is good. Swap within bytelanes as you wish. Do > not swap between bytelanes.Why not ? -- :wq ^X^Cy^K^X^C^C^C^C
Reply by ●January 30, 20072007-01-30
On Jan 30, 9:32 am, "tullio.grassi" <tullio.gra...@gmail.com> wrote:> I am trying to understand if there is any side-effect of pin-swapping. > As an example, I was thinking to pin swap data lines of a Flash > memory; but I realized that these devices have special commands > sent on the data bus, so commands would > get screwed-up (and myself too :)Well, yes - but this is easily handled with macros in your program. This sort of thing is very common.
Reply by ●January 30, 20072007-01-30
On Jan 30, 9:47 am, Ico <use...@zeev.nl> wrote:> > The datasheet's advice is good. Swap within bytelanes as you wish. Do > > not swap between bytelanes.>Why not ?Because you lose the ability to address individual bytelanes uniquely if you mix them up like this.
Reply by ●January 30, 20072007-01-30
larwe <zwsdotcom@gmail.com> wrote:> > > On Jan 30, 9:47 am, Ico <use...@zeev.nl> wrote: > >> > The datasheet's advice is good. Swap within bytelanes as you wish. Do >> > not swap between bytelanes. > >>Why not ? > > Because you lose the ability to address individual bytelanes uniquely > if you mix them up like this.Of course, I'm sorry, for some reason I misread your previous answer, I thought you ment to swapy *between* bytelanes, not *within*. My wrong. -- :wq ^X^Cy^K^X^C^C^C^C
Reply by ●February 3, 20072007-02-03
"tullio.grassi" ...> I am trying to understand if there is any side-effect of pin-swapping. > As an example, I was thinking to pin swap data lines of a Flash > memory; but > I realized that these devices have special commands sent on the data > bus, so commands would get screwed-up (and myself too :)Nope, not the data bus but the address bus - DO NO swap those lines... Regards, Arie de Muynck