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