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SDRAM initialization

Started by Jim Stewart July 15, 2006
I'm writing a new bios for an x86 processor
with an integral SDRAM controller.  I have
it working with the SDRAM, but I'm troubled
by a specification in the SDRAM datasheet that
requires a precharge of all banks to be issued
upon powerup.

As far as I can see, there is no way to run
a specific SDRAM "command".  Will a write to
all banks accomplish the precharge?


Jim Stewart wrote:
> I'm writing a new bios for an x86 processor > with an integral SDRAM controller. I have > it working with the SDRAM, but I'm troubled > by a specification in the SDRAM datasheet that > requires a precharge of all banks to be issued > upon powerup. > > As far as I can see, there is no way to run > a specific SDRAM "command". Will a write to > all banks accomplish the precharge?
This information is sometimes hidden away, usually near the MRS command and data register. A write is not the same as a precharge (look carefully at the commands - if you don't have a datasheet, go to this page for a typical SDRAM from Micron: http://www.micron.com/products/partdetail?part=MT48LC16M16A2BG-75) and get the datasheet. [I suggest Micron simply because they have the best datasheets]. Do you have a link to the specific device you are using? That might enable us to help. Cheers PeteS